Exotic Small Mammal Care and Husbandry

Exotic Small Mammal Care and Husbandry

Exotic Small Mammal Care and Husbandry

Ron E. Banks, DVM, DACLAM, DACVPM, CPIA Julie M. Sharp, DVM Sonia D. Doss, M.Ed., RLATG Deborah A. Vanderford, DVM

All authors are staff at the Office of Animal Welfare Assurance, Duke University, Durham, North Carolina

A John Wiley & Sons, Inc., Publication

Edition first published 2010 © 2010 Ron E. Banks, Julie M. Sharp, Sonia D. Doss, Deborah A. Vanderford Blackwell Publishing was acquired by John Wiley & Sons in February 2007. Blackwell’s publishing program has been merged with Wiley’s global Scientific, Technical, and Medical business to form Wiley-Blackwell. Editorial Office 2121 State Avenue, Ames, Iowa 50014-8300, USA For details of our global editorial offices, for customer services, and for information about how to apply for permission to reuse the copyright material in this book, please see our website at www.wiley.com/wiley-blackwell. Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by Blackwell Publishing, provided that the base fee is paid directly to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923. For those organizations that have been granted a photocopy license by CCC, a separate system of payments has been arranged. The fee codes for users of the Transactional Reporting Service are ISBN-13: 978-0-8138-1022-5/2010. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Disclaimer The contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and should not be relied upon as recommending or promoting a specific method, diagnosis, or treatment by practitioners for any particular patient. The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of fitness for a particular purpose. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. Readers should consult with a specialist where appropriate. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read. No warranty may be created or extended by any promotional statements for this work. Neither the publisher nor the author shall be liable for any damages arising herefrom. Library of Congress Cataloging-in-Publication Data Exotic small mammal care and husbandry / Ron E. Banks . . . [et al.]. p. ; cm. Includes bibliographical references and index. ISBN 978-0-8138-1022-5 (pbk. : alk. paper) 1. Exotic animals. 2. Pets. I. Banks, Ron E. [DNLM: 1. Animal Welfare. 2. Veterinary Medicine. 3. Animal Husbandry. Animals, Domestic. SF 745 E96 2010] SF413.E96 2010 636–dc22 2009041421 A catalog record for this book is available from the U.S. Library of Congress. Set in 9.5 on 11.5 pt Sabon by Toppan Best-set Premedia Limited Printed in Singapore 1 2010

4.

Contents

Acknowledgments

vii

1

Introduction

3

2

Enrichment

11

3

Preventive Medicine

21

4

Rabbits

49

5

Ferrets

61

6

Mice

73

7

Rats

81

8

Gerbils

93

9

Hamsters

103

10 Guinea pigs

115

11 Chinchillas

125

12 Degus

137

13 Hedgehogs

143

14 Sugar Gliders

157

15

169

Opossums

Index

175

Color plate appears between pages 80 and 81

v

Acknowledgments

The authors acknowledge the many unnamed and on occasion unknown contributors to our education and training in the field of husbandry and veterinary medicine. No accomplishment is a singular achievement, and without the assistance of many this book would not have been possible. Thank you. It is the desire and hope of the authors that this text will be used for the betterment of the animals with which we share this globe and for improvement of the condition and environment in which they live. Our commitment to

strong and effective stewardship of the conditions in which we and animals live is the highest ideal one can assign to a human-and-animal relationship; the engaged manner of our compassionate care and our progressive husbandry is the best reflection of our humaneness. The authors wish to acknowledge Mr. Ian Thomas for all line drawing illustrations as well as the following individuals for assistance with photographs: Amy M. McArdle, CVT, LATG; Dan Johnson, DVM; Judi Fox, Cynthia Prevost, and Dorcas O’Rourke, DVM.

vii

Exotic Small Mammal Care and Husbandry

1

Introduction

The role of the veterinary technician continues to develop and mature. Although historically the duties allotted to the veterinary technician have been supportive and responsive—that is, do what you are told when you are told to do it—the current, progressive veterinary climate offers increasing levels of responsibility for engagement. Principal to the modern veterinary technician is the ability to have a dramatic impact on the well-being of the pet by educating the pet owner and assisting with building and maintaining a strong relationship of stewardship and compassion of the pet owner with the pet. To best accomplish this task, the veterinary technician must clearly understand the impact of a variety of factors, both intrinsic and extrinsic, and the role each factor may play in the health and well-being of the small mammal pet. Any list of factors that affect the well-being of a pet would be incomplete, but to provide an outline for this discussion we should consider those in the following list as having the potential to affect the pet’s well-being: • • • • • • • • • • •

Genetics Age Gender Immune status Circadian rhythms Endocrine system Cage design Bedding choices Cage accessories Enrichment strategies Watering options

• • • • • • • • • • • • • • • • •

Feeding options Temperature Humidity Thermal neutral zones Ventilation Illumination Noise Transportation Overcrowding Isolation Social ranking Handling Chemicals used in sanitation Air quality Water intake Feeds and diets Adventitial diseases

The take-home questions for any discussion such as this are: • What is the pet owner doing that may impact the well-being of the pet? • Is the impact of those actions improving or detracting from the well-being of the pet? We will discuss the factors affecting the pet’s well-being by considering those which are intrinsic and those which are extrinsic.

INTRINSIC FACTORS AFFECTING WELL-BEING

Intrinsic factors are those that are inherent to the animal, including genetics, age, sex, health, 3

4

nutritional status, immune status, circadian rhythms, and endocrine factors.

Genetics Although genetic factors generally are not a concern for small mammal species, excessive inbreeding may present a spectrum of disease states which interfere with the well-being of the pet. For example, malocclusion in a rabbit is highly heritable, especially in selected lines, and will interfere with normal nutrition and regular animal-initiated activities. Malocclusion may interfere with grooming, and it will interfere with selecting and chewing preferred foodstuffs. Pet owners should be discouraged from breeding their own pets because they generally do not have sufficient numbers of animals to provide a varied genetic stock and because additional animals may also add to the abundance of unwanted pets. Breeders must have genetic diversity if they are to maximize a strong and healthy population of pet animals. Even in the best of circumstances, mismating, spontaneous mutations, chromosomal aberrations, and residual heterozygosity may result in undesirable offspring. Afflicted offspring should be neutered; if not, at least they should be prevented from mating.

Age Neonatal animals have an immature immune system. That may oversimplify the situation, but it is important to note that the very young are susceptible to conditions or circumstances which would not be important to older animals. Rodents less than 1 week of age are exothermic, which means they cannot control their body temperature. Neonatal pups or kittens, when removed from the nest, will become hypothermic relatively quickly. As a general statement, these young animals begin to develop their “internal furnace” around 1 week of age, and by 6–8 weeks of age are fully capable of maintaining a steady core body temperature. Age becomes critically important when considering placement of the cage in a room where the windows allow sunlight and there is variable air flow. A stable, and even warm, place is important for the well-being of neonatal animals. Although not as pronounced, the same kinds of concerns exist for the very old animal too. In both cases the status of

Exotic Small Mammal Care and Husbandry

immune function is important as neither the very young nor the very old can successfully mount a strong immune challenge to infection. The geriatric animal is prone to increased disease states as the organ systems begin to fail; the young animal is prone to similar concerns, but because of physiologic systems that are not fully functional at the time of birth. This is often species dependent: a guinea pig is “precocious” and ready for all that life can throw at it, whereas a ferret requires weeks of nurturing and care to survive to healthy adulthood.

Gender Gender may also mark an important consideration for animal well-being. For example, 80% of New Zealand White female rabbits will have uterine adenocarcinoma by 4 years of age; males are not affected (as they obviously lack a uterus). Biomedical research has shown a clear distinction between the susceptibility of mammary tumors to certain chemicals and gender. In the Wistar-Furth rat, 100% of females, but only 19% of males, will develop mammary tumors to DMBA (a carcinogenic chemical used in breast tumor research).

Immune system Immunologic dysfunction (including hypersensitivity and allergy, autoimmunity, and immunodeficiency) may influence experimental outcome. A litany of agents or situations can alter immune function, such as age, nutritional status, a host of chemicals, various drugs, select food additives, many metals, and specific microbes. In certain circumstances, the immune response may be decreased (most common) or increased in response to the interference of outside agents.

Circadian rhythms Many behavioral, biochemical, and physiologic parameters (daily, rhythmic, minima and maxima) occur at specific times. For example, blood counts and coagulation times, plasma steroid, body temperature, sensitivity to audiogenic seizure induction (in gerbils), drug metabolism and toxicity (e.g., anesthesia and analgesia), and susceptibility to neoplasia are influenced by circadian rhythms. Although the veterinary technician may not be able to impact most of these items by modulating circadian

Introduction

rhythms, it is worthwhile to recognize that circadian rhythms may impact therapies, enrichment strategies, and outcomes of the pet patient.

5

approach is generally desirable (e.g., rodents’ preference for solid floors over wire floors), it must be managed for its effectiveness (e.g., a preference for sunflower seeds may interfere with generalized nutrition and well-being).

Endocrine factors Sex hormones are important determinants of hepatic cytochrome P450 enzyme activity. Castrating male rats decreases the ability to biotransform xenobiotics and, by extension, can affect the required amount of anesthetic for subsequent events (i.e., castration may extend the effectiveness and duration of anesthesia). Neonatal gonadectomy of select strains of mice leads to high incidence of estrogen-secreting adrenal tumors; so if small mammals are to be neutered, awaiting puberty in the species may be worthwhile. EXTRINSIC FACTORS AFFECTING WELL-BEING

Extrinsic factors are those that are external to the animal and include physical factors (macroenvironment vs. microenvironment, cage design, caging accessories), chemical factors (air, water, diet, and drugs), microbial agents, stressors, and environmental factors (temperature, humidity, ventilation, illumination, and noise).

Physical factors The single most important thing a veterinary technician can do is to stop thinking of small mammals as small humans. Just because humans would like something does not mean it is a good choice for the small pet. The focus of consideration for the pet’s well-being is the animal’s environment: The microenvironment is the environment immediately surrounding the animal. It may be the cage, the pen, the box, or the room. The microenvironment is where the animal lives. By extension, the macroenvironment is where the animal’s container is maintained—the macroenvironment is where the humans live. Although the macroenvironment contributes extensively to the microenvironment, one must be principally focused on the “nose of the beast” to achieve a preferred, healthful, supportive, and enriching microenvironment. One way to state it is “what is the animal’s preference?” Even though this

Cage design The style or design of the cage used for housing the animal affects its well-being. All other factors being the same, cage design can determine the amount of air, light, and sound the animal receives. Cage design can also impact the amount of heat, humidity, and gaseous waste dissipated into the macroenvironment. Again, all items being equal, plastics or polycarbonate caging materials tend to be an acceptable compromise for most situations. Plastics filter the light, diminish the sound, and foster a stable microenvironment (heat or cool). However, if not properly ventilated, plastics may also limit the amount of fresh air available and thus increase ammonia level, humidity, and the risk of airborne infection. Studies generally indicate that static (plasticwalled) caging is preferable to slatted wirewalled caging for most small mammals. Many pet owners choose slatted wire-walled cages because it allows for increased “communication and interaction” with their pet, but such caging can have significant disadvantages. For example, a slatted wire-walled cage will allow free exchange of air, but air flow through an accumulation of fecal matter is not a good idea. The preferred caging design is one that provides for normal physiologic and behavioral needs, allows conspecific social interaction, facilitates development of hierarchies within or between enclosures, remains clean and dry, has adequate ventilation, assures access to food and water, serves as a secure environment, is free of sharp edges, and allows an animal to be observed with minimal disturbance. Cage accessories should receive the same general consideration as caging materials. Items that come in direct contact with the pet should be nonreactive, nonpalatable, smooth and impervious, durable, corrosion resistant, and sturdy. In certain specific situations natural materials such as wood may be used, although the wood should be in the form of branches from pesticide-free trees, without signs of tree disease or damage, and replaced frequently to

6

prevent ingestion or allow for it to become unsanitary. Wood of certain trees may have undesirable products (e.g., tannins in oak, aromatic hydrocarbons in pine and cedar) that could negatively impact the pet animals, and therefore such wood should not be used. Galvanized metal and rubber stoppers may be used, but only if the animal shows no interest in chewing or licking the metal or rubber. Both the zinc in galvanized metal and the rubber of the stopper may have a negative impact on the animal’s well-being.

Water Too little water is not good and too much water is not good either. Water should be checked daily, as lack of water can kill in as little as 24 hours! Many small animals will not eat if they are not able to drink; considering that most animal feeds are dry kibble, an absence of water may also result in feed intake concerns. In species with a large cecum or appendix (e.g., guinea pigs and rabbits), where the microbes are dependent upon a fluid environment, lack of sufficient water may also result in gut dysbiosis and could result in disease from microbial toxin production or dieoff of desirable microorganisms.

Feeders The style of feeder used for a species is dependent upon the needs of the species, but all feeders have common criteria for selection. A feeder should allow access to food, minimize contamination with feces and urine, and accommodate group housing considerations, which may require multiple feeding and watering points, while also optimizing the diet consumption.

Temperature and humidity Species-specific temperature and humidity preferences are reviewed in the species chapters, but certain generalized concepts and issues remain. Management of a stable environment is the most critical aspect of temperature and humidity. Constantly changing temperature and humidity is more harmful to the well-being of the animal than any specific temperature (within reason of course). A general recommendation for all species is 30% to 70% relative humidity. Although there is little evidence for strict control of relative humidity, it is also

Exotic Small Mammal Care and Husbandry

true that variations in relative humidity are better tolerated at lower temperatures, due to heat loss mechanisms of most animals. Low relative humidity may be more associated with pollution- (e.g., ozone and dust) associated respiratory disease while high relative humidity may be more closely linked to infectious disease (e.g., fungi and bacteria) transmission. Temperature extremes also have an effect on other aspects of animal care and support. Lactating rats exposed to 95 °F (35 °C) for 6 hours daily produced less milk than rats housed at 72 °F (22 °C) Reproduction in rats also decreases markedly at 90 °F (32 °C) (e.g., retarded testicular development).

Thermo-neutral zone The thermo-neutral zone (TNZ) is that range of temperatures where no energy is expended by an animal to either cool or heat itself. The TNZ differs by species and does not necessarily relate to the comfort of the animal. As a general rule, animals are most comfortable at a temperature toward the low end or just outside of the low TNZ temperature. Exposure of unadapted animals to temperature higher than 85 °F or lower than 40 °F without access to shelter may produce clinical effects that could be life threatening. If the temperature change is of short duration and low magnitude, then few signs are expected and even fewer will be observed. However, if the temperature deviation continues (duration and magnitude), animals will exhibit huddling, curling up, nest building, and increased general activity (all are signs indicating a desire to remove itself or protect itself from the environment). If the deviation continues further (duration and magnitude), animals will alter their metabolism rate and will consume more water and more (or less) food; the growth rate will also be affected. In cases where the temperature changes are colder, animals will enter into hibernation, torpor, or aestivation, will begin nonshivering thermogenesis (brown fat utilization), will have peripheral vascular changes shunting more blood to the core of the body and away from the appendages (the tail of rodents is used for thermoregulation to eliminate excess heat), and will exhibit piloerection (hair standing up).

Introduction

If the temperature deviation (duration and magnitude) lasts for 14–21 days, then the body increases its fat stores, thickens the fur coat, and significantly restricts heat radiation.

Ventilation The purpose of ventilation in most circumstances is to remove thermal loads, dilute gaseous and particulate contaminants, and adjust moisture content. Few, if any, pet cages are so secure that oxygen needs of the animal are ever in doubt. The macroenvironment of most homes provides a fresh air exchange of one to two air changes per hour. Adequate room ventilation does not necessarily ensure adequate ventilation of the microenvironment! Although not generally a concern, if ammonia in the cage is high or the bedding remains moist for extended periods, then the cage’s location should be considered and perhaps changed or a supplemental fan should be provided to assure a sufficiently dry cage. Because small mammals may also cause an allergic response, a response that can be cumulative, it is generally preferable to maintain the cage as close to an exhaust air duct as possible, but not immediately adjacent to the exhaust vent to prevent strong drafts that can stress the animal.

Illumination Small mammals are generally crepuscular (more active at dusk or dawn). They do not require light as intense as humans and in fact will tend to withdraw from intense light levels. They will adjust to the light schedules we use in our homes, but left alone small mammals prefer 14 : 10 (light/dark) to 10 : 14 (light/dark). Increasing or decreasing light levels can affect breeding receptivity in some species, but less so in others. Albino animals have pink eyes and are relatively more susceptible to phototoxic retinopathy than pigmented species. Albino animals, if maintained in continuous light, can develop blindness within 18 months. Illumination can also affect medicinal treatment through hepatic enzyme activation. During the light cycle, rodents given a barbiturate will sleep longer than rodents given the same dose during their dark cycle. It is important to ask the pet

7

owner whether the animal is kept exclusively indoors (where light and dark are generally the same year round) or whether the animal is principally an outdoor animal (where light and dark cycles may vary significantly over the year). As a general guideline, small animals require only 325 lux (approximately 30 footcandles) of light for normal function and development.

Noise Noise is a significant factor for the well-being of small animals, but it is rarely considered. Small animals tend to hear at a higher frequency compared with humans, but most also hear well at the human upper end (yes, heavy rock music is heard by the pet rat). Noise levels around animals should never exceed 85 dB as auditory effects of noise can occur at >85 dB. The effects are dependent upon the intensity of the noise and the duration (either point or cumulative) of the noise event. Destruction of sensory hairs and supporting cells can start at 90 dB, mechanical damage in rats occurs at 160 dB, and pain has been reported in rats at 140 dB. Rats have developed inner ear damage after prolonged exposure to 100 dB. Noise also produces direct physiologic effects. Increases in serum cholesterol and in adrenal weights occur in rats exposed to 83 dB and intermittent sound of 114 dB. Audiogenic stress due to pulsed noise exceeding 83 dB may cause reduced fertility in rodents, and audiogenic seizures occur in gerbils and select strains of mice. Radios, alarms, and timers should not be placed close to small animals. Computer video screens, large fans, and other household motors frequently have ultrasounds that can be highly distressful to small animals. These devices should not be used near small animals unless they have been checked for ultrasonic frequencies. In some cases, artificial background noise may be useful in masking sudden unexpected noise.

Transportation Any time the animal leaves its home cage, it is being transported—usually just for a trip to the backyard but sometimes much further. Transportation can be a significant stressor for these species, requiring an acclimation period after

8

transportation before “normal” signs are once again observed. Adolescent rats require 1–5 days for complete physiologic recovery after being transported. The use of a similar cage, with familiar accessories, the same food, and some of the same water can lessen the effect of the transport. During transport, animals should be protected from sunlight or wind by placing an opaque cover over the cage. The vision system of animals sees things differently from humans, and the rapid and repeated movement that occurs during transit can be highly stressful. If transport occurs in a vehicle the cage should be secured on the floor or seat of the car using a bungee cord or similar device to prevent tumbling in the event of a quick stop. Care should be taken to secure the top and bottom of the cage to prevent dislodgement and escape of the animal during transit.

Overcrowding and isolation Animals are generally social creatures (certain exceptions occur during breeding season or due to reproductive processes). Animals may experience adverse conditions from being either overcrowded or isolated. Overcrowding can be mitigated to some degree by effective utilization of enrichment paradigms (e.g., hiding boxes, red film). In many cases, aggressive behavior will be strain- or even sex-specific. Group-housed mice show marked adrenal response that is directly proportional to the animal density. In these conditions, the subordinate animal has the higher adrenal weight and plasma cortisone level due to its stress associated with being subordinate. Once social groups have been established, fighting may occur if the groups are reassorted or if a new member joins the group. Breeding and reproduction can also be influenced by group housing. Grouped-housed rodents frequently become anestrous and will synchronize the estrous cycles in the presence of a male (Whitten and Bruce effect).

Handling Regular and gentle handling reduces animal stress and decreases the risk of fear-provoked biting. Correct handling and restraint techniques are critical. Failure to handle gently and correctly may result in injury to the animals and to the handler. The ears of the rabbit are

Exotic Small Mammal Care and Husbandry

not genetically placed handholds, and the tail of a mouse was not placed there so you could safely pick it up. Veterinary technicians have a special duty to teach and train pet owners on proper methods of restraint and handling.

Chemicals The potential list of chemicals that could negatively impact animals would be an entire study in toxicology, but we shall concentrate on general concepts and issues related to chemical exposure. Air, feed, water, bedding, and caging materials may all present potential chemical concerns. Chemicals may enter via damaged skin, the intestinal tract, or the respiratory tract. While the list of potential effects of chemical insult is long, the more common outcomes are changes in the hepatic microsomal enzymes, the biotransformation of medications, and the regulation of oxygen radical removal (associated with cancer development). Chemicals may serve as local irritants, produce generalized disease, alter immune functions, provide allergen exposure, be a source of mutagen, or even function as a teratogen.

Air quality Air quality is not simply an argument for clean air or sufficient air, but rather for appropriate air. Air can become a disadvantage for these small mammal species. At 68 °F (20 °C), air moving at 60 linear feet per minute has a cooling effect of 45 °F (7 °C). Air this cold, no matter how clean, can significantly stress the animals, especially the neonate or the geriatric animal. High airflow also has a “wash-out effect” upon pheromones. Clean air is not necessarily a good concept either. Because animals communicate by pheromone, in some cases even to the exclusion of verbal communication, elimination of pheromones prevents the creation of a “home sweet home” for the pet and never allows its complete integration into the cage environment. Air can also be excessively dirty. Humans can sense airborne ammonia at around 25 ppm (parts per million). Animals begin to show respiratory impact of elevated ammonia at 10 ppm. In some cases, low-level ammonia enhances the potential disease impact. Mycoplasma pulmonis, in the presence of low-level ammonia, will

Introduction

have an increased severity of lung lesions, enhanced growth of the organism, and greater adherence (decreased clearance) of secondary bacteria in the lungs.

Water quality Most pet animals are provided drinking water from the home tap. In some cases, it is wonderful water, but in other cases, it may be a concern for the pets and their owners. Although most municipal water is treated with chloramines to discourage bacterial growth, high levels of chloramines may affect the immune system. Stressed or injured animals may benefit from filtered water until their return to a healthy state.

Diets Dietary requirements are addressed in the species chapters of this text, but they deserve a general mention in our review of external factors that may affect the well-being of the pet. Likely the most common cause of dietary modification is provision of treats. Many pet owners will use treats to encourage specific behavior to get the pet to eat. Treats should be limited and never exceed 5% of the total required dietary intake of the animal. Variations in quantity or quality of essential vita-

9

mins or minerals may alter drug metabolizing systems, affect membrane integrity, or predispose to the effects of carcinogens. In certain cases, selection of specific treats may serve to benefit the animal’s well-being, as in the case of vitamin C requirements and guinea pigs, or roughage requirement and rabbits. In all cases, diet milling date and storage conditions should be monitored because fat-soluble vitamins will be leached when stored at high temperatures and other vitamins may lose potency if stored for excessive periods of time. Just because it looks like a pelleted pet ration doesn’t mean it is worth feeding to the pet. The most important concern for a dietary discussion is to avoid abrupt diet changes; when changes are required, do so over a period of 2–3 weeks if possible. Although not as habitual as other animals, these small mammals can benefit from changing the feed from time to time and familiarizing them with alternate feedstuffs. Such planning has on occasion facilitated the medical management of a sick patient when presented with diets different from those served at home.

Adventitial diseases Diseases common to particular species will be addressed in each of the species chapters.

Enrichment

The strong and interactive relationship between a pet and its human companion serves to benefit both. If we begin with the premise that “animals are what make us humane” (another way to say it is “animals are the basis for our compassionate relationships to other creatures, including humans”), then our desire to maximize their environment and make their lives as comfortable as possible becomes a logical reason for considering enrichment of the pets’ environment. Recognizing the bond that exists between humans and animals, as well as the value animals bring to the human existence, makes the desire to enhance the environment of animals an easy discussion. Enrichment in many contexts simply means creating an environment that both allows and encourages species-specific activities. For example, rodents like to burrow and aquatic species like to hide behind or within structures. If we provide a deep layer of soft sand for the aquatic creatures and a box for the rodent pet, we haven’t caused any harm, but we have missed an opportunity to make their environments as “normal” as possible. “Normal” is quite difficult to truly assess in animals, especially those that have never seen the out-of-doors. Our perceptions of normal must be guided by the animal’s interest in and motivation to use the enrichment item. Even though many captive animals have never lived in the “wild,” enrichment strategies can be guided by the natural habitats and behaviors of their wild counterparts. A clear recognition of normal is critical to a complete patient assessment as well as selection of enrichment

2 strategies for the patient under consideration. If you are unaware of normal, how will you be able to assess a change, either positive or negative, in the animal you are observing? Knowing normal is the key to quality enrichment of the animal’s life! Development of an ethogram is one way to determine normal. An ethogram compares the time budgeted by the animal for a given task or activity. By observing the actions or activities from a range of options, one can deduce that this animal finds greater satisfaction with activity A over activity B. The more the observations, the more confidence one has in the outcomes of animal ethograms. A word of caution is necessary at this point: each of us would rather eat candy than swim four lengths of the pool, but we would all agree that the pool exercise would be more beneficial, especially if performed daily. Consideration of animal “preferences” using educated judgments can guide the technician in selecting beneficial activities or devices for the environmental enrichment. The goal of an enrichment strategy is to improve (or maintain) the health of the animal. Animals that are active and engaged in their environment are also generally more healthy than those that sit quietly for hours and hours with little to do and nothing to explore. “Doing” is a part of being healthy. Enrichment can also be used as a tool for assessing the health and well-being of animals. Animals that lack exploratory behavior may be in discomfort from osteoarthritis or other disease states. Providing enrichment through exploratory 11

12

behavior (e.g., hiding treats in grass, in hay, or inside boxes), especially when provided just prior to the dark cycle, will decrease stereotypic behaviors common of poorly enriched animals. Keen observation of an animal during enrichment activities will provide several useful clinical tools for assessing the condition of the patient. Observation of an animal’s activity level is one method the veterinary technician may use to “hear” what the animal is saying. Enrichment falls into two general categories: social enrichment and nonsocial enrichment. Social enrichment requires interaction of the animal with other animals or with humans. Social enrichment may include time spent holding, petting, walking, or playing with the pet. Social enrichment is important to decrease the pet’s anxiety or “reactiveness” to humans. Generally speaking, an animal that has spent significant quantities of time with humans, and has been handled gently during those interactions, is less likely to bite or scratch than one that has had limited human contact or rough handling. However, having human social interaction is not the only way to provide enrichment to the animal. Often, conspecific interactions (e.g., interaction with one’s own kind) are the most advantageous. Conspecifics already understand the language of the species; they recognize common odors, see common visuals, and react in a similar manner to other stimuli. In other words, conspecifics already know how to read moods, respond appropriately, and communicate readily. For social species, whenever possible, animals should be housed with members of their own species. In certain cases, there are restrictions on how conspecific housing should occur. For example, hamsters raised alone and then grouped as adults will often attack and severely injure each other. Rats, however, are highly social animals and, given the option, will curl together when sleeping and will be in close contact when awake. These are examples of direct social enrichment. Social enrichment may also be indirect. Animals may be placed nearby, but without the ability to touch. Since most small animals communicate in a hearing range above human hearing (ultrasound), proximity of location may provide good social enrichment while pro-

Exotic Small Mammal Care and Husbandry

tecting the individual animals. Although not the same as direct contact, being able to hear each other and see each other may provide sufficient interaction to decrease stress and improve well-being. Mirrors may be used for animals that have well-developed sight, but shiny surfaces can also be a detriment, especially if the animal is frightened by reflections or is an individual that is aggressive toward other members of its species. Seeing a reflection in a mirror can stimulate social behavior, encourage activity, and even provide for a sense of companionship. Exercise can be either social or nonsocial. Small mammals may be transferred from their home cage to an exercise pen for various periods of time. The novelty of the exercise pen will stimulate the pet and encourage exploration. The use of an exercise pen also requires that we consider the advantages and disadvantages of such an arrangement, especially if there are multiple species using the same area. The exercise pen should be sanitized effectively between uses. Most of the small mammal species are either prey or predator, depending upon the context of the moment. A rat is generally considered a predator to a mouse, but if a ferret were introduced, then the rat could be considered the prey species. Placing a ferret in an exercise pen, then removing it and placing a rat in the same pen without sanitation, would not be a pleasant experience for the rat: it would sense the predator animal and would be more concerned with escaping and evading the predator than with the novelty of curious exploration. Small rodents, especially gerbils, mice, and rats, are thigmotactic, meaning they prefer to be near a wall than in an open space. Knowing this, one should consider maximizing wall surfaces as an enrichment strategy and, to the extent possible, minimizing the wide-open spaces in the home cage or the enrichment pen. This can be accomplished by use of tunnels, boxes, or other devices that provide wall surfaces. Small mammals (e.g., rodents, rabbits) are crepuscular, a term used to describe animals that are primarily active during twilight (either or both dawn and dusk). There are two behavioral relationships of such animals that can facilitate selection of an appropriate environment and care strategy.

Enrichment

First, crepuscular animals have decreased bright light vision and enhanced dim light vision. The best overall enrichment strategy for these animals includes protection from direct or intense sunlight. Crepuscular animals will be most active when the lights are low. Light in most homes is at the high end of the preferred intensity for small mammals, so decreasing light levels by turning off a light or two may increase the pet’s activity level. Using a night light in the pet’s room may simulate a moonlit night and, for crepuscular species, may keep the animal active most of the night. Second, crepuscular animals lack the ability to sense red or yellow light. We can take advantage of this knowledge by surrounding a sleeping box with red or yellow color (e.g., a film or a plastic sheet). The animal will believe it is dark, but humans can view the animal inside. Using a red or yellow film may allow good observation of the patient without the patient being aware it is being observed. As an aside, the definition of crepuscular includes the terms matutinal (or matinal, indicating activity at dawn) and vespertine (indicating activity at dusk). Most small mammals prefer one or the other, but will have activity during both time periods. In addition to exercise, proper caging selection can be considered a nonsocial enrichment. Sanitizable products (e.g., metal, plastics) are generally preferable to nonsanitizable products (e.g., wood). Certain metals should be avoided (e.g., zinc–coated metals, copper, and iron) as these products can be ingested or absorbed into the animal’s system and cause disease. From a sanitary standpoint, the use of hard plastic or metal provides an easily sanitizable surface. However, from the perspective of an animal’s well-being, such materials can be highly disruptive to the animal’s comfort. Metal is cold and hard, and plastic can be too. Both products are nonabsorbent, preventing the segregation of waste products in the environment. Some have suggested the use of wire mesh or screening for animals. In theory it allows waste products to migrate from the animal’s environment and keep the animals dry. However, studies have shown that animals prefer hard surfaces to wire surfaces. When considering that a geriatric animal may have difficultly moving on wire or that a heavy animal may have ulcers or feet

13

sores from the wire surface, the use of wire flooring in most applications is not recommended. A modification of the wire flooring concept is the slatted floor, where the surface is composed of flat bars approximately ¼ inch wide or larger. These floors are preferred to wire and do assist in keeping the animal dry and clean, but they do not allow for bedding products and, depending upon the caging type, may be drafty for the animal. In most applications, the preferred outcome is a compromise between the most easily sanitizable environment and the most enriched environment. For burrowing animals, providing clean, absorbent, and soft material on a solid nonporous surface (e.g., plastic) to dig and construct nests and passageways allows the animal an opportunity to explore, to follow its curiosity, and to build its “home.” At times, the compromise between providing soft and absorbent materials and providing materials that can be effectively sanitized becomes troublesome. Selection of an appropriate substrate for the comfort of the animal while assuring effective sanitation often requires the use of different materials (e.g., a hard easily sanitizable surface for the exterior and a soft absorbent material for the interior). For most species, cage placement is a critical item. For example, the placement of the cage near a window could offer some species an enriching atmosphere with novel stimuli during the course of the day; for others, especially guinea pigs, placement near a drafty window would provide short-term enrichment but increase the infectious disease potential (e.g., guinea pigs are highly stressed by drafty conditions). Placement near a window also requires close monitoring of the cage temperature. Sunlight streaming through on a sunny day can increase the cage temperature above the optimal range in a very short period of time, even to dangerous levels. Small mammals are more tolerant of cold than of heat, and they can rapidly develop hyperthermia when in direct sunlight. When we remember the crepuscular nature of many of these species, most will sleep during the day; thus the placement near a window for novel stimuli becomes more of a health concern than an enrichment advantage. The cage environment is another variation of nonsocial enrichment. Cages may have

14

hiding places and foraging opportunities (hiding feed in burrows, burying feed in Astroturf, mixing a desirable feed into the fibers of a sheet of synthetic fleece, or other similar devices that encourage the animal to “work” for the feed reward). The cage environment may also include balls, mobile toys, oddly shaped items to chew, natural wood products, or even small sections of fabric that were used by the human companion (a small square of old bedding used by the human companion will have residual human scents that can facilitate a familiarity between the animal and the human). Natural products, such as branches or leaves, should be removed and replaced when they become excessively soiled with excrement. Bedding can serve an enormous role in the well-being and enriched environment of these animals. The amount of bedding used should be sufficient to keep the animal dry between cage changes, without coming into contact with watering devices. Bedding selection is also an important variable affecting the well-being of the pet. Bedding made of softwood products such as pine or cedar may affect the animal’s metabolism and may in some cases actually interfere with recovery from anesthesia or even disease states. For example, red cedar shavings are commonly used for pet bedding because the red cedar smells fresh. That fresh smell is principally two aromatic hydrocarbons (cedrene and cedrol) that induce specific liver enzymes, which can alter rates of anesthesia and interfere with metabolism of certain medications. Likewise, spruce and pine shavings contain alphapinene, another volatile hydrocarbon that also induces hepatic enzymes. Heat treatments (such as autoclaving) can reduce the concentration of aromatic hydrocarbons and might prevent induction of hepatic microsomal enzymes. Hardwood shavings (beech and aspen) or corncob chips are generally preferred over the softwood beddings. Hardwood products do not have the volatile compounds found in softwood products. Hardwood is absorbent and can serve as effective bedding material. Hardwood bedding is available in a variety of chip sizes (to be discussed later). Hardwood may also cause injury to the neonate or the infirm

Exotic Small Mammal Care and Husbandry

from the sharp edges commonly found on the chips. Paper products, depending upon the source and processing of the paper, may be useful to consider, but there may also be disadvantages with these products. Paper may have residual ink or bleaching agents that may affect their use. Fibrous products can be very useful for small mammal bedding. The long fiber length facilitates nest building, encourages manipulation, and provides enhanced opportunity for foraging. Disadvantages may include the source of fibrous products. Corn or beet husks may have residual fungal contamination if not properly treated (generally autoclaved) and managed (kept cool and dry). These concerns with fungal interference intensify when the fibrous products become wet. Bedding type also affects thermoregulatory stability, core temperature, and motor activity. Mice housed on deep bedding maintain significantly higher core temperatures during the day. During the night, however, core temperatures and motor activity show no difference, probably more related to activity on the bedding rather than burrowing into the bedding. Although deeper bedding has a positive impact upon core body temperatures, deep bedding can also present a risk of touching the water bottle sipper and draining the bottle of water, wetting the bedding, and causing hypothermia in the caged animals. In this case, the deep bedding presents the opportunity to injure the animal rather than to support its well-being. Animals do have preferences for certain types of bedding. Beddings consisting of relatively small particles (1.2 mm × 1.6 mm) are generally avoided by rodents, whereas large fibrous bedding materials are preferred by mice and rats. Size and manipulability are among the main determinants of the appreciation of bedding particles by mice and rats. Lastly, when considering the air in the cage, ammonia is the single most common and most important airborne pollutant in the pet cage. Certain beddings have a higher ammonia generation potential than do other bedding materials. The following bedding materials are ranked from highest to lowest in ammonia generation potential: aspen shavings; pine shavings; reclaimed wood pulp; loose virgin pulp; hard-

Enrichment

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wood chips; recycled paper; pelleted virgin cellulose; and corncobs. We must note, however, that routine and regular cage cleaning can overcome concerns with ammonia generation in any of the bedding products. How then should a bedding product be assessed for supporting the well-being of the pet? An ideal bedding material should be dust free, nonpalatable, absorbent, and free of microbial and toxic contaminants. No bedding is ideal for all species. No bedding is ideal for all care conditions. However, bedding is a controllable environmental factor—one that may enrich or detract from the environment! A good place to start is with hardwood bedding. Feed products may also be used as a means of enrichment, though overfeeding of supplements can have deleterious effects. All pets require a nutritious ration. Small pets consume small quantities of feed, and provision of too much enrichment feed can interfere with the required basic nutrition of the pet. As a general rule, supplements and food enrichments should not exceed 10% of the standard diet. Feed supplements must also be selected based upon the species. Rabbits enjoy carrot tops, but should not be given too many carrots (excessive amounts of carrots can cause gastritis and

subsequent gastrointestinal distress). Guinea pigs enjoy green leafy vegetables such as kale, but should not be given iceberg lettuce since it has almost no nutritional value and may cause GI distress in large volumes. Hamsters and gerbils are hoarders and prefer to hide feed for eating at a later time; providing at least some of the ration on the floor of the cage and mixed into clean bedding is a more natural situation for these species and will foster positive behaviors (as opposed to feeding in a food bowl, or especially feeding with a wire-bar hanging lid). Rodents enjoy oil seeds (e.g., sunflower seeds), but the quantity should be restricted since given the choice rodents will consume only sunflower seeds and develop nutritional deficits by failing to consume sufficient balanced ration. At other times, the use of supplementation can have medicinal value. Although most animals internally manufacture the components of vitamin C and therefore do not require vitamin C in the diet, guinea pigs are one species that cannot, and therefore must consume sufficient quantities of vitamin C or they will develop scurvy. Providing guinea pigs a small enrichment of a citrus fruit (e.g., orange, lemon), especially if the ration being fed is not

Table 2.1 Rodents (mice, rats, hamsters, gerbils, degus): These normal behaviors should be considered in the development of an overall strategy of enrichment. Gnawing

The teeth of many rodents grow continually and, without gnawing, will overgrow and cause pain or disease. Gnawing is a critical life behavior for rodents.

Burrowing, hiding, daylight sleeping

Rodent eyes are sensitive to intense light, such as occurs during the day. Burrowing is one method of escaping from intense sunlight.

Exploring, climbing, seeking feed

Rodents are “explorers”; they prefer to search for their food as a means of “normal” food acquisition. Hiding feed encourages exploration, increases exercise, and provides normal behavior.

Grooming

Grooming of one’s cage mates is a strong social activity that builds bonds of trust and relationship. Grooming also serves as basic sanitation for the coat, removing excess debris and dander while combing and smoothing the fur.

Nesting

Nesting is a behavior that consolidates the “family,” provides social contact, facilitates grooming, and gives a sense of a thigmotactic environment.

Thigmotactic

Rodents do not have good vision; therefore they depend upon their whiskers and sensory fibers around the head and shoulders. Rodents prefer being next to a wall and will choose a close and confined space rather than an expanse of floor.

Neophobia

Although novel stimuli are useful, presentation of new-tasting food enrichments will generally be met by a small nibble, then restraint from further consumption until time has passed. This evolutionary survival mechanism prevents the ingestion of poisonous foodstuffs. Novel foodstuffs may initially be rejected but subsequently preferred to another novel introduction.

Table 2.2 Guinea pig: These normal behaviors should be should be considered in the development of an overall strategy of enrichment. Scatter, freeze

When sensing “danger,” the guinea pig will do one of two things: either run quickly to a less dense location or freeze in place and hope the danger passes.

Linear hierarchies

Guinea pigs form strong relationships to other guinea pigs in the area. Separating or regrouping animals may engender unnecessary distress.

Territorial

Guinea pigs are strongly territorial. They do not readily accept newcomers and will chase or corner new inhabitants.

Vocalizations

Guinea pigs have a large repertoire of sounds and inflections to communicate their intentions. This is one species where vision is less important than indirect communication such as vocalization.

Cover

Being a burrow-dwelling rodent, guinea pigs prefer some form of cover to be “safe.” Enrichment strategies should always include opportunities to hide.

Table 2.3 Rabbit: These normal behaviors should be considered in the development of an overall strategy of enrichment. Chewing

Rabbits require regular chewing to maintain proper apposition of the front teeth.

Thumping

Rabbits do not vocalize very well or very frequently, but rather use thumping as a means to communicate their message. Often associated with an aggressive posture, thumping can be the harbinger of an aggressive action to follow.

Locomote (hop or roll)

Rabbits use these maneuvers to escape or evade. Rabbits in a playful mood may also exhibit these behaviors.

Nudging, nose

Rabbits use nudging as a softer means of communicating (softer than thumping). The rabbit will press its nose in the direction it desires the opponent to move.

Fur pulling

Does will pull their fur immediately prior to kindling to provide soft down for their kits.

Grooming

Rabbits groom constantly, never satisfied with the present status of things. Rabbits that are prevented from grooming may appear depressed.

Table 2.4 Ferret: These normal behaviors should be considered in the development of an overall strategy of enrichment. Alligator roll

This is a behavior important for establishing dominance between two animals. Single animals may grab the socks, feet, or loose skin of their human companions in an attempt to “alligator roll” them.

Backing into a corner

This is a behavior seen for urinating and defecating, but it may also be a sign of fear. If the animal hisses, the fear response is likely. Picking up these animals can result in serious injury.

Bottle brush, “puffy” tail

A “puffy” tail, or “bottle brush tail,” is an indication of fright or excitement. Other signs should also be noted (hissing would be fear) to determine the actual meaning of this sign.

Chasing or lunging

This is a playful behavior.

“Dancing”

Jumping from side to side in a playful series of antics, “dancing” is generally a sign of excitement, but it may also be an indication of aggression.

Dooking or chirping

This is the sound made while excited.

Food, water, litter-pan digging

This is a normal behavior where the animal digs for its feed or for a place to defecate. This can occur at any time and, while not harmful, can be a mess to clean up.

Food or water bowl tipping

This is a behavior probably related to the curious and digging nature of the animal.

Hissing

Hissing is a behavioral sign of fear or anger or a show of intimidation.

Running into things

This is not necessarily a behavior of its own; ferrets have poor eyesight and, when in a hurry, can run directly into things—or off a balcony or stairs.

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Enrichment

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Table 2.5 Sugar glider: These normal behaviors should be considered in the development of an overall strategy of enrichment.

Table 2.7 Chinchilla: These normal behaviors should be considered in the development of an overall strategy of enrichment.

Nocturnal

Social

Chinchillas are highly social and active animals that like companionship. In their natural habitat, they live in herds ranging up to 100 or more animals.

Nocturnal

They are most active at night and sleep during the day. Eating occurs at night.

Fur dropping

Frightened animals will “drop fur” rapidly.

Chirps or squeaks; barks

These are common communication sounds indicating any number of expressions from play to fear.

Sugar gliders have acute night vision, but limited day (bright-light) vision.

Vocalization They often vocalize for no apparent reason, but likely for simple communication. Social

In nature they may be found in groups of 30–50.

Territorial

Sugar gliders use urine and scent glands to identify territory (even humans).

Table 2.6 Hedgehog: These normal behaviors should be included in an overall strategy of enrichment. Curling

This is a behavior to indicate “enough,” or simply a need to escape for a time.

Anointing, or anting

Production of a large amount of foamy saliva when they encounter an unfamiliar smell—they will lick at the novel item until frothy saliva develops, then rub the saliva on their quills. This is the process of anointing, also called anting.

Chirping, whistling, purring

These are sounds indicating comfort and contentment—a happy hedgehog.

Snorting, hissing, clicking

These are sounds indicting discomfort, fear, or aggression—an unhappy hedgehog.

Foraging for food

Digging and climbing are beneficial hedgehog behaviors.

Solitary

These are not social animals and should be housed separately.

Diurnal

They are most active at dawn and dusk, although some remain on the move until 3 a.m. Frequent handling during the day can help change the hedgehog’s habits and help reduce the nighttime activities.

fresh, will prevent the development of this disease while also providing a pleasing enhancement to the regular diet. Enrichment strategies should always be developed in the context of the natural behavior of the animal. For example, rodents generally have limited vision but a well-developed sense of smell and hearing. Providing visual stimulation to the pet rat or gerbil will likely not provide an enriching activity. However, providing items that stimulate the sense of smell or the sense of hearing may be far more engaging and satisfying to the animals. All animals have certain behaviors, sometimes based upon physiological needs (e.g., gnawing in rodents to keep the teeth trimmed). Examples of behaviors include those given in Tables 2.1–2.7.

ENRICHMENT STRATEGIES

Enrichment strategies must be considered species by species. The types and styles of enrichment for one species can be inappropriate for another species. Enrichment strategies should be formulated according to the normal behaviors of the pet; therefore it is key to clearly recognize normal behavior in a species prior to recommending any enrichment strategy.

Rodents Almost any item that is nontoxic and safe can be used as part of a rodent enrichment strategy. These may include the following: • Bedding (burrowing and exploring for rodents)

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• • • • • • • • • • • • • • • • • • • •

Burrows (generally a plastic product) Cage dividers (increasing wall surfaces) Climbing accessories Exercise devices (running wheels) Film canisters Foraging devices Tunnel (provides closeness and wall surface) Gnaw blocks or sticks Group or social housing (not hamsters, adult male mice, or female rats) Hide boxes Ladders Mazes Soft music Nest boxes or nest-building material (hay, tissues, or wood-wool) Platforms PVC pipe (½- to 1-inch diameter is best) Ramps Shelves Shuttle box (also called transport box) Tubes (such as those from rolls of toilet tissue or paper towels)

Rabbits Almost any item that is nontoxic and safe can be used as part of a rabbit enrichment strategy. These include the following: • • • • • • • • • • • • • • • • •

Balls (hard plastic) Bedding (straw, wood chips) Burrows (oatmeal cans, boxes) Free range (e.g., a clean and pesticide-free backyard) Fresh fruits or vegetables (limit sugary fruits; use more vegetables) Gnawing objects (aspen wood or apple wood) Group housing Soft music Nest boxes Nesting material (tissues, straw, dust-free hay) Pair housing (except adult males) PVC pipe Resting shelf Roughage or forage (limit alfalfa; prefer grass hay) Varied diet Suspended shiny objects Brass “canning rings” (tough enough to chew, soft enough to bend)

Exotic Small Mammal Care and Husbandry

Ferrets Almost any item that is nontoxic and safe can be used as part of a ferret enrichment strategy. These include the following: • • • • • • • • • • • • • • •

Balls Bite cups Crickets Foraging devices Fur-covered movable toys Hammocks Hide-and-seek tunnels Mazes Moving preymodels Music Nest boxes Plastic burrows PVC tubes Shelters Swimming pans

Sugar glider Almost any item that is nontoxic and safe can be used as part of a sugar glider enrichment strategy. These include the following: • • • • • • • • • • • • • • • • •

Bedding Burrows Cage dividers Climbing accessories Climbing frame Foraging devices Group or social housing Hide boxes Mazes Soft music Nest boxes or nest-building material (hay, tissues, or wood-wool) Platforms in cages PVC pipe (2- to 3-inch diameter is best) Ramps Shelves Shuttle box (also called transport box) Tubes (such as those from rolls of toilet tissue or paper towels)

Hedgehog Almost any item that is nontoxic and safe can be used as part of a hedgehog enrichment strategy. These include the following:

Enrichment

• • • • • • • • • • • • • • • •

Bedding Burrows Cage dividers Foraging devices Group or social housing Hide boxes Ladders Mazes Soft music Nest boxes or nest-building material (hay, tissues, or wood-wool) Platforms PVC pipe (2- to 3-inch diameter is best) Ramps Shelves Shuttle box (also called transport box) Tubes (such as those from rolls of toilet tissue or paper towels)

Chinchilla Almost any item that is nontoxic and safe can be used as part of a chinchilla enrichment strategy. These include the following:

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• • • • • • • • • • • • • • • • • •

Bedding Burrows Cage dividers Dust baths Foraging devices Group or social housing Hide boxes Ladders Mazes Soft music Nest boxes or nest-building material (hay, tissues, or wood-wool) Platforms PVC pipe (2- to 3-inch diameter is best) Ramps Sand bath Shelves Shuttle box (also called transport box) Tubes (such as those from rolls of toilet tissue or paper towels)

Preventive Medicine

Veterinary technicians are often required to consult and advise clients concerning the health of their pets and the potential diseases that may be transmitted to the client’s family. Even more frequently, veterinary technicians work alongside the veterinarian in diagnosing and treating communicable diseases. A clear understanding of the potential diseases that our pets, or our patients, may share is crucial for the veterinary technician to achieve maximum impact. Let’s begin, therefore, with the recognition that we have a closely intertwined relationship with our pets and our animal charges. We live with animals and we work with animals. Diseases that we may pick up at work can affect our pets at home, and diseases at home can affect the health of our patients at work. Animals can carry a number of diseases that are important to our pets—and our family members. The term for diseases transmitted between animals and humans is “zoonoses.” The World Health Organization defines zoonoses (zoonosis, sing.) as “Those diseases and infections which are naturally transmitted between vertebrate animals and man.” The effects of zoonotic disease may be direct illness, negative feelings of family members about the pet, monetary cost of treating the disease, potential legal implications if the animal infects or injures a neighbor child, and the loss of the friendship and companionship of the animal due to unmitigated disease. Recognizing zoonotic disease and the potential for zoonoses is an important aspect of quality medical service. However, before discussing specific zoonoses,

3 we must understand a few basic concepts about zoonotic disease. There are five primary modes of zoonotic disease transmission: fecal material, urine, blood, saliva, and milk. Certain of these modes of transmission are easy to envision. For example, fecal contamination has and will make people ill; parasites and other diseasecausing agents are often transmitted in fecal material. Other methods of transmission may not be as obvious; for example, saliva is not something we think we are sharing with our patients, but as they groom themselves they are spreading their saliva on their fur coat. We then pet them or brush them, and in addition to removing loose fur we are also removing dried saliva proteins or potentially infectious particles. Recognizing the mode of disease transmission is important to understanding how to limit the spread of disease. Each of these primary modes of transmission may be further subdivided according to the specific route by which a contagion gains admittance to the body: aerosolization (breathing in airborne contaminants), mucous membrane (touching our mouth, eyes, or nose with contaminants on our hands), or contact with the bedding or animals (this route may include direct contact with the skin). Considering these routes of infection, and adding the modes of transmission, we can see that washing our hands to protect ourselves from fecal or urinary output may not be sufficient. Fecal material may dry out, releasing small particulate matter that becomes airborne and is subsequently inhaled. 21

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Knowing the mode and route of infection is not sufficient alone to clearly understand the probability of disease transmission from animals to humans. The probability of developing a disease is influenced by several factors, including the following: A. Length of time the animal is infective: Animals with parasitic diseases often are infective for years. Animals with viral diseases often are infective for days to weeks. B. Length of the incubation period in animals: For diseases with long incubation periods, infected animals may be observed as “normal” for long periods of time, because the animals may move housing locations or even die before becoming infective for humans. C. Stability of the agent in the environment: Enveloped viruses (e.g., canine coronavirus, murine hepatitis virus) are less hardy and can be more easily destroyed by common disinfectants than nonenveloped viruses (e.g., feline leukemia, parvovirus, rabies), which are very hardy and may persist for long periods of time. This factor is most important in direct transmission, where the virus may be exposed to environmental changes. D. Population density of the animals in the home or clinic: Large concentrations of animals spread disease more rapidly than few animals in a common location. E. Husbandry practices: Daily sanitation, especially when tied to an appropriate disinfecting chemical, can disrupt or break the infectious cycle and prevent transmission of disease. F. Control of wild rodents and insects: Generally, wild animals have a variety of infectious agents, some of which may be significant to the pet or the client. G. Virulence of the agent: Another way to think of virulence is how “hot” is the agent, or how “aggressive” is it, or how “rapidly will it spread?” For example, Coxiella burnetti requires only 10 organisms to cause disease, whereas Pasteurella generally requires thousands of organisms to cause disease.

Exotic Small Mammal Care and Husbandry

H. Route of transmission: Viral infections more readily result from mucous membrane contact than “palm of the hand” contact. Zoonoses may also be classified in a number of ways. A useful system of classification is based on the type of life cycle of the infective organism. This system is most practical and seems the most useful in planning a preventive medicine program. The following categories are recommended by the World Health Organization Expert Committee on Zoonoses: A. Direct zoonoses: Agent is transmitted from infected vertebrate host to a susceptible vertebrate host by direct contact, fomite, or a mechanical vector. No developmental change or propagation of the organism occurs during the transmission. Examples are rabies, trichinosis, and brucellosis. B. Cyclozoonoses: Agent requires more than one vertebrate host, but no invertebrate host. Examples are human taeniasis, echinococcosis, and pentastome infections. C. Metazoonoses: Agent multiplies, develops, or both in an invertebrate host before transmission to a vertebrate host is possible. (This means that a definite prepatent or incubation period must be completed before transmission.) Examples are arboviruses, plague, and schistosomiasis. D. Saprozoonoses: Transmission of these infections requires a nonanimal development site or reservoir, such as food plants, soil, or other organic material. Examples are larva migrans and some of the mycotic diseases. The direction of disease transmission is also worthwhile knowing. For example, if a disease is common in animals and easily transmitted among animals but only rarely infects humans, then the control and prevention measures are very different from a disease that is shared readily and equally between humans and animals. The manners of describing the direction of transmission are as follows: Anthropozoonoses: Infections transmitted to humans from lower vertebrates. Zooanthropozoonoses: Infections transmitted from humans to animals.

Preventive Medicine

Amphixenoses: Infections maintained in both humans and lower vertebrates; may be naturally transmitted in either direction. Zoonoses may also be organized by etiologic (causative) agent. This is the structure we will follow for our continuing review: A. Bacterial 1. Bacteria 2. Spirochetes 3. Chlamydia 4. Rickettsia 5. Mycoplasmas B. Fungal C. Viral D. Parasitic 1. Protozoan 2. Helminth a. Nematode b. Cestode

BACTERIAL DISEASES

Systemic infections Brucellosis Agent: Brucellosis is caused by the following organisms: Brucella Brucella Brucella Brucella

abortus—cattle, sheep canis—dogs melitensis—sheep, goats suis—swine

Reservoir and incidence: Of the preceding species, we will only casually recognize the significance of the agricultural impact of B. abortus. Instead we will focus our attention on B. canis, once considered the most likely zoonotic agent, due to extensive numbers of roaming animals. Even today, the prevalence of Brucella may be as high as 10% in dogs in the US and the UK, and substantially higher in other parts of the world (e.g., Mediterranean and Arabian Gulf regions, Latin America, Africa, and Asia). Brucella canis is well adapted to dogs and is not the subject of any large-scale eradication program in the general dog population, as Brucella has been in agricultural animals. Humans appear to be quite resistant to B. canis infection, although occa-

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sionally it has been transmitted to humans. Veterinarians and veterinary technicians exposed to the blood of infected animals are the primary risk populations; pet owners are generally considered not at risk of this disease, except in the cases where there are immunecompromised people (e.g., cancer patients, HIV-infected individuals, transplantation patients). These groups should not handle infected dogs. Transmission: There are two recognized modes of transmission of B. canis: 1. Most likely cause for technicians—contact with infected animals, especially aborted fetuses, fluids or membranes, or urine 2. More likely cause for pet owners—airborne Disease in animals: In animals, the disease may cause the following: 1. Abortions 2. Infertility, testicular abnormalities, poor semen quality in dogs 3. Inapparent infection, which may also be common, as indicated by seropositivity (presence of antigen or antibody) Disease in humans: In the few human cases recorded, bacteremia was a fairly common finding, along with lymphadenopathy, splenomegaly, fever, headache, chills, orchitis, weakness, nausea, and weight loss. However, many of these same symptoms could be caused by the annual flu outbreak or any number of other minor diseases. Diagnosis: A rapid slide agglutination test is available. Standard tube agglutination has been used, and a 2-mercaptoethanol test can distinguish an active disease from a recovery from earlier illness. In certain cases, blood cultures and additional serologic tests may be used to confirm slide test results. Treatment: The therapy varies by geography. Generally, tetracycline/streptomycin combination has been used in the United States, whereas doxycycline/rifampin combination has been the preferred option in Europe.

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Prevention and control: Although the risk is low, individuals working with suspect positive animals should use disposable gloves and protective eyewear. Chlorine, oxidizers, organic iodine, and quaternary ammonium compounds are rapid bactericidal agents.

Exotic Small Mammal Care and Husbandry

reservoir is swine (pharynx may be heavily colonized), so veterinary care of swine— whether farm-reared or pet pigs—should include consideration of this agent. There have also been cases of this disease associated with caring for sick puppies and kittens but without a clear connection to swine.

Yersiniosis Agent: Animals are susceptible to three Yersinia species that are potentially zoonotic, all of which are gram-negative, rod-shaped bacteria: (1) Y. pseudotuberculosis; (2) Y. enterocolitica; (3) Y. pestis.

Yersiniosis—Y. pseudotuberculosis Agent: Yersinia pseudotuberculosis are gramnegative, non-spore-forming rods. Reservoir and incidence: This organism is ubiquitous in nature and can be isolated from dust, soil, water, and milk. Natural infections occur in humans, birds, rodents, rabbits, guinea pigs, mice, cats, nonhuman primates, sheep, swine, and goats. Direct zoonotic transmission has been documented from rabbits to humans, although other species may potentially transmit the disease as well. Transmission: Yersinia is generally transmitted by fecal contamination in food or water. Good feed and water sanitation will disrupt most transmission from animals to humans. Disease in animals: Guinea pigs, rabbits, and hamsters exhibit poor condition and enlarged lymph nodes. Nonhuman primates exhibit ulcerative colitis. Disease in humans: Humans exhibit mesenteric lymphadenitis, which can be confused with appendicitis and septicemia. Diagnosis: Isolation using cold enrichment technique (difficult to isolate).

Yersiniosis—Y. enterocolitica Yersinia enterocolitica (sometimes called Pasteurella X disease) causes a form of yersiniosis that may produce gastroenteritis in humans, with an acute watery diarrhea. On rare occasions, it may produce a mesenteric lymphadenitis that mimics appendicitis. The primary

Yersiniosis—Y. pestis Agent: Yersinia pestis is a gram-negative rodshaped bacteria and is the causative agent of plague. Reservoir and incidence: This disease is endemic in certain wild rodent populations in southwestern United States as well as in Africa and Asia. Plague surveys have also found evidence of this agent widespread in wild animal populations all across the western Great Plains region of the United States. Whereas prairie dogs and select peromyscus (deer mouse) and related species are reservoirs in the United States, the more important reservoirs worldwide are the roof rat, Rattus rattus, and the urban rat (sometimes also called the Norwegian rat), R. norvegicus. In the United States, from 1970 to 1995, a total of 341 cases of human plague (average, 13 cases per year) were reported (CDC, 1996). The disease is also associated with cats, goats, camels, rabbits, dogs, coyotes, prairie dogs, and fox squirrels. Cats have been the source of infection in several human cases. Domestic cats are a principal cause of human pneumonic plague in the United States. Persons working in veterinary practices should be especially aware of the risks involved in handling Y. pestis–infected cats. Dogs and cats may serve as passive transporters of infected rodent fleas into the home. Transmission: The primary method of transmission involves contact with infected rodent fleas (over three-quarters of human cases) or direct rodent contact. Fleas may remain infected for months, so the disease may be apparent, go into “hiding,” and recur at a later time. A protein secreted by Yersinia serves as a coagulase that causes blood ingested by the flea to clot in the proventriculus. The bacillus proliferates in the proventriculus, and thousands of organisms are subsequently produced. The flea regurgitates to clear its obstruction after biting

Preventive Medicine

an animal or person. The material is injected intradermally or subdermally, and a new infection is born. This coagulase produced by the organism is inactivated by high environmental temperatures and this is believed to explain the disruption of plague transmission during very hot weather—the blood fails to coagulate and the organisms cannot reproduce in the flea’s proventriculus. Human infections from nonrodent species usually result from direct contact with infected tissues, by scratch or bite injuries, and handling of infected animals. The pulmonary form of this disease is often rapid in onset and dramatic in its incapacitation of the patient; the disease results from airborne or droplet infection from infected animals. Disease in animals: In dogs, this is generally a brief self-limiting illness. In cats, the disease is often severe and a fatal infection, with fever, lymphadenopathy, hemorrhagic pneumonia, and encephalitis. Cats may also develop a long-term infection resulting in the development of abscesses containing thick, creamy pus. Rodents may carry the disease asymptomatically (the method of the disease surviving a “hot environmental spell”) or develop fatal disease and die. Disease in humans: Incubation of the plague agent is 2–6 days; it may be called bubonic, septicemic, or pneumonic plague depending on the pattern of distribution of the infection. Bubonic is the most common form, causing fever and swollen, tender lymph nodes (called buboes). Pneumonic plague is systemic plague with lung involvement. Mortality may exceed 50%.

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5. Radiographic examination of the thorax will help determine whether the animal has pneumonic plague and, thus, whether aerosol transmission is a danger. Treatment: Streptomycin with tetracycline or chloramphenicol is commonly used to treat the infection. Prevention and control: The easiest and most effective recommendation for prevention of this disease is the elimination of wild rodents in and around the home and fleas on the family pet. In some areas of the world where endemicity is present, public health departments provide a sentinel animal program. There are vaccines available for high-risk personnel, but these are not often required. If you suspect an infected animal, isolate the animal, use appropriate gloves and protective clothing, and treat with an effective parasiticide (if eliminating the fleas) or an appropriate antibiotic.

Tuberculosis Agent, reservoir and incidence: Tuberculosis (TB) is caused by the gram-positive, acid-fast, aerobic bacillus of the Mycobacterium genus. The three most common species of mycobacteria and their susceptible hosts are the following:

Diagnosis: This disease is diagnosed by:

1. M. bovis (susceptible hosts include most warm-blooded vertebrates) 2. M. avium–intracellulare complex (susceptible hosts are birds, swine, sheep, cattle, mink, dogs, cats, humans, and cold-blooded animals) 3. M. tuberculosis (susceptible hosts are humans, nonhuman primates, dogs, and swine)

1. Impression smears of aspirates or blood stained with Gram’s or Giemsa’s stain. Organisms have a typical “safety pin” appearance. 2. Culture of the organisms can be performed by reference laboratories. 3. Fluorescent antibody (FA) assay of smear is confirmatory. 4. Serology via complement fixation, passive hemagglutination, and immunofluorescence [indirect fluorescent antibody (IFA) assay].

In addition to the “common” forms of TB, there are also uncommon forms that occur in certain situations. “Atypical Mycobacterium,” M. scrofulaceum, M. kansasii, and M. intracellulare, have been reported in monkeys and may be present in soil and water. People who keep primates as pets, especially if these individuals or members of their family are immunocompromised (due to other diseases such as HIV), should be alert for pulmonary disease that can be resistant to treatment. The incidence of

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human TB has decreased dramatically in the past several decades due to the Bovine Test and Eradication Program and the availability of effective therapy. Tuberculosis does still occur in humans in the United States and other countries. Although all three types are capable of causing disease, M. tuberculosis (var hominis) is by far the most common. Currently, the incidence of human tuberculosis is increasing as a result of the AIDS epidemic. The late 1990s saw an increase in the number of human cases, reversing a declining trend from the middle of the century up until the mid-1980s. The rise in human tuberculosis is also complicated by a rise in drug-resistant cases. Nonhuman primates may carry all three forms of the disease, but most infections found in pet animals are caused by M. tuberculosis var hominis; this is an example of an anthropozoonosis. In close confinement the disease can spread rapidly. Transmission: Mycobacterium bacilli are transmitted from infected animals or infected tissue primarily via the aerosol route, but the disease may also be contracted via ingestion or cutaneous inoculation of the bacilli. Personnel caring for infected animals as well as those performing necropsies on infected animals are at higher risk for contracting the disease. Exposure to dusty bedding of infected animals, coughing of infected animals, and aerosolization of the organism during sanitation procedures may also be sources of the disease in the veterinary hospital environment. Once within the body the organism may spread throughout the lungs, lymphatics, blood vascular system, and many visceral organs. Disease in nonhuman primates: Signs of TB may be insidious with only slight behavioral changes noticed, followed by anorexia and lethargy. Often animals die suddenly while appearing, up to the point of death, as being in good condition. Other signs that might be seen include diarrhea, suppuration of lymph nodes, ulceration of the skin, and palpable splenomegaly and hepatomegaly. The organ of predilection is the lung, but lesions may also be seen in the pleura, intestines, lymph nodes, liver, kidney, spleen, and peritoneum. Under the surface of these tissues are yellowish-white to

Exotic Small Mammal Care and Husbandry

gray nodules filled with caseous material that may rupture and produce cavitation. Although skeletal involvement is rare, tuberculosis of the spine may cause paralysis of the hind limbs, commonly called Potts disease. Disease in humans: In humans the clinical signs depend on the organ system involved. The most familiar signs related to pulmonary TB are cough, sputum production, and hemoptysis. The human patient may be asymptomatic for years. General signs may include anorexia, weight loss, lassitude, fatigue, fever, chills and cachexia. Tuberculosis may affect virtually every other organ system, with signs or symptoms relating to the individual system. Miliary TB may be more often associated with the very young or old people. Cutaneous TB is also called pathologist’s wart. Mycobacterium avium ssp. paratuberculosis (formerly M. paratuberculosis) has been implicated as a possible cause of Crohn’s disease in people. Diagnosis: The diagnosis of TB is often difficult. Three tests are commonly used for presumptive diagnosis: Animals are generally diagnosed by an intradermal TB test, radiography, or an acid-fast stained smear. In cases where the animal has died, histopathology may also be used. Prevention and control: The best measures of prevention include a multifaceted approach of pet owner education (especially if the owner has immunocompromised individuals in their lifestyle and there are primate pets involved). A regular health surveillance program for humans and monkeys is critical to catching the disease during the early phases, and it offers the best surveillance tool for this disease. Although a vaccine is available in Europe, it is not used in North America because it results in a positive TB test, which requires additional assessment tools to rule out active infection. The vaccine, BCG (Bacille Calmette-Guerin) is a modified strain of M. Bovis and is effective when used in high risk groups. Isoniazid therapy is currently effective in treating nonresistant mycobacterial strains, but the survival of this disease for thousands of years would suggest prevention is the better option than attempting to cure the disease.

Preventive Medicine

Listeriosis Agent: There are seven recognized species of Listeria, with L. monocytogenes and L. ivanovii considered pathogenic—presumably related to the presence of a hemolytic enzyme, listeriolysin O. Listeria are gram-positive, small pleomorphic rods. Reservoir and incidence: This agent is isolated from fish, birds, swine, horses, ruminants, guinea pigs, ferrets, gerbils, rabbits, and chinchillas. Transmission: Oral and conjunctival routes are most common but other means of transmission can occur. Cutaneous listeriosis appears to be the occupation-related form most likely acquired by animal care and technical staff. In one case, reported in a dairy farmer who assisted in delivering a calf, the organism was subsequently isolated from vaginal pustules on the cow. Disease in animals: The signs observed with this disease depend in some part upon the species infected. For example, in rabbits, vaginal discharge, abortion, and metritis in pregnant does is common; in rodents and birds it is more likely to find generalized septicemia; in ruminants, encephalitis or mastitis may be seen. Disease in humans: Cutaneous involvement, coryza, conjunctivitis, metritis with abortion, sepsis, and meningitis all have been reported in humans. Most cases of listeriosis develop in people who are immunocompromised, elderly, or pregnant or who have handled fetal or newborn tissues from infected animals while not using adequate personal protective measures. Diagnosis: This is not an easy organism to culture and will require special media and laboratory equipment. Prevention and control: Caution and protective clothing when handling infected tissues are the best measures to prevent an infection from this agent.

Leptospirosis Agent: The agent is a spirochete, Leptospira (130 serotypes).

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Reservoir and incidence: Most animal species have one or more serotypes of Leptospira that may infect them. Rats, mice, field moles, guinea pigs, gerbils, squirrels, rabbits, hamsters, reptiles, nonhuman primates, livestock, and dogs have all been reported to host leptospira organisms. Up to 40% of stray dogs have been found to be seropositive to one or more serotypes of Leptospira. Rodents (especially rats and mice) can host and shed L. ballum throughout their entire life and during shedding may not exhibit any clinical manifestations. This is a unique feature of rodent infection with leptospires. On occasion the first indication of an infected animal will be reports of human infections with this agent. Transmission: Infection generally occurs from handling affected animals or tissues, contaminating hands or abrasions with rodent urine, or aerosol exposure during cage cleaning. There is a single case of a mother transmitting the disease to her breast-fed infant, presumptively through the breast milk, although fomite contamination from the environment could not be ruled out. Disease in animals: In animals, the disease is generally inapparent but conjunctivitis, pneumonia, jaundice, and hemorrhage have been reported. Pet monkeys have exhibited hepatic necrosis and interstitial nephritis. Abortion and persistent renal infections have also been reported in some animals. Generally speaking, host-adapted strains produce mild illness in the host animals, with nonadapted strains causing more severe disease in the new species. Disease in humans: The disease in humans ranges from inapparent infection to severe infection and including death. There is generally a biphasic illness that consists of weakness, headache, myalgia, malaise, chills, and fever, followed by leukocytosis, painful orchitis (testes not usually enlarged), conjunctival effusion, and rash. Diagnosis: This agent has a characteristic presentation under a silver stain such as Warthin–Starry, but serological diagnosis and isolation of organisms and culture are necessary for definitive diagnosis. Culturing leptospires is

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difficult and requires several weeks. Serology is accomplished by indirect hemagglutination, agglutination, complement fixation (CF), microagglutination, and FA techniques. The “preferred test” is the Modified Microtiter Agglutination Test. A 1 : 100 or greater titer is of diagnostic importance. Leptospires can be recovered only from mature mice even though antibodies can be detected from infected mice of all ages. Treatment: Chlortetracycline, dihydrostreptomycin, penicillin G, and amoxicillin have all been used effectively to treat this disease. Leptospira ballum was eliminated from a rodent breeding colony (mice) by using 1,000 g chlortetracycline HCL/ton of feed for 10 days. Prevention and control: The best prevention in this case is vaccination of cattle, swine, and dogs. There are no vaccines for rodents or other pets.

Lyme disease (borreliosis) Agent: This agent varies around the world. Borrelia burgdorferi is found in the United States and Canada; B. garinii and B. afzelii are found in Europe; B. japonica is found in Japan and Asia. Incidence: Borreliosis was first implicated in 1982 as the causative agent in a 1975 epidemic of juvenile inflammatory arthropathy in Old Lyme, Connecticut, and named after the town where the disease occurred. Lyme disease is now considered endemic in more than 23 states and southeastern Ontario, Canada. It is the most frequently reported tick-associated disease in North America. With over 15,000 cases reported annually, eight states accounted for 91% of the nationally reported cases (Connecticut, Rhode Island, New York, New Jersey, Delaware, Pennsylvania, Maryland, and Wisconsin, from most to fewest cases reported). Reservoir and incidence: Lyme disease is transmitted principally by Ixodes spp. ticks. Ixodes are three-host ticks with a 2- to 3-year life cycle. Larvae feed primarily on rodents, especially mice. Nymphs feed on all hosts and are primarily responsible for transmission of the disease to people. Infected ticks must be

Exotic Small Mammal Care and Husbandry

attached to the host for approximately 48 hours before spirochetes are transmitted. Ixodid ticks have a broad range of hosts. Ixodes scapularis is the primary vector in the eastern and midwestern United States, I. pacificus on the Pacific Coast of the United States, I. ricinus in Europe, and I. persulcatus in eastern Russia and Eurasia. Peromyscus leucopus, the white-footed mouse, is the primary reservoir in the northeastern United States. The deer mouse (P. maniculatus), chipmunks (Tamias striatus), voles (Microtus pennsylvanicus), house mice (Mus musculus), Norway rats (Rattus norvegicus), and rabbits (Oryctolagus cuniculus) can also transfer infection to ticks, but with less efficiency than the white-footed mouse. In northern California the dusky-footed woodrat (Neotoma fuscipes) is the primary reservoir, and I. pacificus serves as a vector for transmitting the disease to humans. In northern Colorado borreliosis transmission is maintained by the Mexican woodrat (N. mexicana) and I. spinipalpis. Cotton rats (Sigmodon hispidus) and rice rats (Oryzomys palustris) are potential reservoirs. Reptiles and birds can be infected with spirochetes, but their role as reservoirs remains poorly defined. White-tailed deer (Odocoileus virginianus) and roe deer can serve as primary hosts of adult ticks, but they do not appear to serve as reservoirs for the spirochete. Recent studies have suggested that arthropod vectors may not be necessary for transmission; in these cases it appears the organism was transmitted by direct contact with mice and dogs. Assuming direct transmission is possible, it is most likely via infected urine; the agent has been found in the kidney and urine of feral hosts. It has also been isolated from blood, cerebrospinal fluid (CSF), tissues, and joints. Transplacental infection has occurred in humans. Spirochetes can penetrate skin, but the public health risk from this mode of transmission is not known. Disease in animals: Clinical signs of infection are not seen in the primary reservoirs. In dogs, diagnosis is usually clinical due to sensitivity and specificity problems with serologic test kits. Signs include transient, recurrent, brief episodes of gait abnormality associated with swollen joints, anorexia, lethargy, and response to antibiotic treatment.

Preventive Medicine

Disease in humans: Multisystemic disease that may have chronic sequelae is the more common finding. An annular rash known as erythema chronicum migrans (ECM) develops in the area of the tick bite. The outer edge of the ECM lesion expands and develops a ringlike appearance as the center of the lesion clears. Human patients may also experience flulike symptoms, which resolve in about 3 weeks. Eight percent of people develop mild cardiac involvement several weeks after infection, which is generally transient. Fifteen percent of affected humans develop neurologic disorders such as facial nerve palsies that usually resolve without treatment. Sixty percent of human cases develop the most common sequelae, arthritis. Disease may remain latent with symptoms developing 4 years after seroconversion. Diagnosis: The recommended test is detection of antibody titers. Evaluation for CSF antibody can be used to diagnose Lyme neuro-borreliosis. Culture of the expanding border of an ECM lesion is definitive but is difficult and requires special media such as Barbour–Stoener–Kelly media. Diagnosis may be made histologically with Dieterle silver stain or immunoperoxidase stains but is often unrewarding. Treatment: Antibiotics such as doxycycline for adults, amoxicillin for children, and intravenous ceftriaxone for active neuro-borreliosis have been successfully used. Prevention and control: Tick control is the best method of preventing the spread of this disease. Technical staff should be careful when removing ticks or when handling potentially infective materials. There are two vaccines currently marketed for dogs, both of which are reasonably effective. For humans, a proposed vaccine containing two “outer surface proteins” (A and B) provides dual protection by protecting the host as well as eliminating the spirochete in the intestinal tract of the attached ticks.

Enteric infections Campylobacteriosis Agent: Campylobacter (Vibrio) fetus ssp. jejuni is a gram-negative, microaerophilic,

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curved, motile rod that is worldwide in distribution. Reservoir and incidence: This agent is commonly found as a commensal in the gastrointestinal tract of ruminants, swine, dogs, cats, fowl, rodents, and monkeys. Of 218 human cases of C. jejuni infection in the northwest United States, 6.3% were attributed to exposure to animals with diarrhea (principally dogs). Many of these cases were diarrhetic puppies from pounds or shelters. Prevalence surveys showed that Campylobacter can be isolated from an average of 25%–30% of all dogs and 10%–15% of all cats tested. Pet birds, chickens, and kittens have also been implicated as reservoirs of this disease. Veterinary technicians have occasionally contracted this disease but usually from cleaning excretions of infected animals. The organism was first isolated in 1979, so it is a relativly “new” disease. Transmission: Transmission is generally via a fecal–oral route, through contamination of food or water, or by direct contact with infected fecal material. The organism has also been isolated from house flies, so good insect control is valuable when sick or diarrhetic animals are present. At 4 °C, the organism is viable for 3 weeks in feces and milk, 4 weeks in water, and 5 weeks in urine. Winter temperatures may preserve the organism rather than eliminate it. Campylobacter may be shed in the feces for at least 6 weeks after infection. Commercial animal feeds have been considered as potential sources of the organism. Disease in animals: Affected animals are generally presented with a history of diarrhea, which may range from excessive soft stool to watery and fetid. Campylobacter may be shed for extremely long periods of time in stool. Carrier animals may not show any signs of disease (they may have “normal” stool). Younger animals seem more likely to acquire the infection, but it is unclear whether the increased infection rate is related more to their generally more curious behavior or to their immature immune system. In either case, young animals have been implicated as more commonly being the cause of the disease. Ferrets appear to be especially susceptible, having

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signs ranging from asymptomatic to proliferative colitis. Ferrets have been shown to shed organisms for up to 16 weeks. Campylobacter has also been shown to cause hepatitis in poultry and abortion in ruminants. Disease in humans: Humans will experience acute gastrointestinal illness, diarrhea with or without blood, abdominal pain, and general constitutional symptoms, without fever. Usually, campylobacter is a brief, albeit painful, self-limiting disease. The asymptomatic carrier state in humans is rare. Reinfection is possible in both animals and humans. Diagnosis: Campylobacter may be identified using dark field or phase contrast microscopy of fecal material. This should be confirmed by stool culture, which requires a special selective growth medium (CAMPY-BAP) and incubation at 43 °C with 10% CO2, 5% O2, and 85% nitrogen. A Warthin–Starry silver stain and histology sections may also be employed. Various seroconversion techniques may also be considered. Treatment: Animals may be treated based on culture and sensitivity. Currently erythromycin is the drug of choice, but it does not eliminate the carrier state. Prevention and control: In select circumstances, vaccines provide partial protection of short duration; however, routine use is not recommended. Control should be aimed at isolation of affected individuals and improvement of personal hygiene. An increased awareness of the potential of infection due to Campylobacter is of primary importance to preventing a common animal pathogen from affecting humans in the area. Related organisms, Arcobacter cryaerophilus and A. butzleri, formerly called Campylobacter-like, also cause diarrhea and enterocolitis in humans. In farm animals they have been shown to cause abortion, stillbirths, and diarrhea. Many consider Arcobacter as a new and emerging human and animal pathogen.

Salmonella Agent: Salmonella is a gram-negative bacteria. It is suggested that all salmonellae belong

Exotic Small Mammal Care and Husbandry

to a single species, S. enterica, with multiple serotypes. Out of 2,296 recognized serotypes of Salmonella, S. typhimurium and S. enteritidis have been associated most commonly with lab animal colony infections. The most frequently isolated serotypes from nonhuman sources in the United States are S. typhimurium, S. enteritidis, S. heidelberg, S. hadar, and S. choleraesuis. A multiple-drug-resistant strain of S. enterica serotype typhimurium known as Definitive Type 104 (DT104) has emerged as an increasing cause of Salmonella infections. DT104 isolates are highly resistant to antimicrobial agents, frequently demonstrating a pattern of resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracyclines. All Salmonella infections, except for S. typhi, S. paratyphi A, and S. paratyphi C, are considered zoonoses. Reservoir and incidence: Salmonella occurs worldwide. Salmonella inhabits the intestinal tract of many animals, including birds, rodents (rats, mice, hamsters, guinea pigs), monkeys, and humans. Salmonella DT104 has been isolated from cats, wild birds, rodents, foxes, and badgers, and it has been transmitted from cattle and sheep to people. The house mouse may also be a reservoir of the infection and may play a role in human and animal salmonellosis. Humans or animals may serve as asymptomatic carriers of Salmonella. Salmonella prevalence in the US canine population has been reported to range from 5% to 10%. In another study, 11% of humane society cats were found to carry Salmonella. Birds, reptiles, and turtles are especially dangerous sources of salmonellosis; over 90% of all reptiles harbor Salmonella. In 1970, turtles alone caused 280,000 human cases of salmonellosis. Responding to the public health crisis, the Food and Drug Administration (FDA), in a 1975 ruling, issued a prohibition against the selling of viable turtle eggs or live turtles with a carapace length <10.2 cm (4 inches). The small “box turtle” was a common pet at that time and the cause of almost all cases of zoonotic salmonellosis in children. After the FDA ruling, there was a 77% decrease in turtleassociated salmonellosis. As a side note, marine (ocean) turtles have not been shown to be a reservoir of Salmonella.

Preventive Medicine

Transmission: This infection occurs via indirect transmission through contaminated food and water. It is possible, but less likely, that transmission may also be by direct contact and inhalation. Salmonella DT104 is associated with contact with sick farm animals and eating contaminated meats. Salmonella is a common contaminant of sewage and is found in many environmental water sources. Environmental contamination (low-lying wet areas, swampy areas) continues to be a potential source of infection for animals and secondarily for personnel handling those animals. Animal feed containing animal by-products may be a source of Salmonella contamination, especially if the diets consist of raw meal and have not undergone the pelleting process. Neonates, old animals, animals with concurrent infections, and stressed animals are most susceptible to disease. Disease in animals: There are five basic patterns of infection in animals: 1. Primary salmonellosis—septicemia, acute enteritis, or chronic enteritis. 2. Concurrent disease or stress—another disease creates conditions making the individual more susceptible to a secondary disease such as salmonellosis. 3. Chronic carrier—shows no signs of the disease, appears healthy yet continues to seed the environment with the disease agent. 4. Temporary carrier—is generally quite ill, but provides large quantities of disease agent to the environment. 5. Latent infection—does not express the disease, appears healthy. Disease in humans: This disease manifests itself as acute gastroenteritis with sudden onset of abdominal pain, diarrhea, nausea, and fever. It may lead to septicemia, or it could show as a long-term inapparent infection. Diagnosis: The preferred manner of diagnosis is fecal culture with selective media. Caution: False negatives do occur because organisms may be shed intermittently. In certain animals, the carrier state bacterium has been localized to the gall bladder (monkeys).

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Prevention and control: Obtain pets from a “clean” source. Treatment should be based on culture and sensitivity, rather than prophylactic therapy that may cause bacterial resistance. Use good sanitation, protective clothing, and gloves when working with suspect animals. Rodent, bird, and wild animal control is important, and cleanup of contamination may be helpful in preventing infection in pets. The best measure of prevention is strong personal hygiene.

Helicobacter Agent: Although there are numerous helicobacters known to science, only Helicobacter heilmannii (H. bizzozeronii) and H. felis have been implicated in zoonotic transmission at this time. Reservoir and incidence: Currently reports are sparse, but because these agents colonize in a small percentage of humans with gastritis (primary species in humans with gastritis is H. pyloris), and no environmental source for these bacteria has been recognized, pets have been implicated as a possible source of infection. Three reports of human gastritis caused by these two species implicate cats and dogs as the probable sources of infection. Helicobacter pylori has recently been isolated from commercially reared cats and it has been shown to experimentally colonize in both dogs and cats. It has also been shown experimentally that the specific (human) strain of H. pylori also infects and induces persistent gastritis in cats. Transmission: This is principally a fecal–oral transmission, although one case suggested a child was infected by repeated exposure to infected dog vomitus. Disease in animals: This disease may range from inapparent infection to active chronic gastritis. Disease in humans: Clinically, the same range of expression observed in animals may also be observed in humans. Diagnosis: Culture, biopsy, and histopathology are the most frequent methods of diagnosis. A urease tissue assay, urea breath test,

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serology, or polymerase chain reaction (PCR) may also prove worthwhile in select cases. Treatment and prevention: Treatment consists of a triple therapy regimen with amoxicillin or tetracycline; metronidazole; and bismuth subsalicylate. Other regimens with reported success include ranitidine or omeprazole.

Respiratory or cutaneous infections Erysipeloid Agent: The agent is Erysipelothrix rhusiopathiae (insidiosa). It was discovered by Robert Koch, who called it the Bacillus of Mouse Septicemia. Reservoir and incidence: A saprophyte of soil, water, and decaying organic matter, erysipelothrix may be a pathogen in pigs, lambs, calves, poultry, aquatic species, and wild and pet rodents. Although many pet species may be affected, pigs probably represent the most likely source of exposure. Zoonotic transmission from pet rodents has not been reported. Transmission: The potential for zoonotic transmission is contamination of wounds by handling infected tissues. Disease in animals: Called Diamond Skin Disease in pigs due to the characteristic lesions. The organism causes clotting in the small arteries of the skin, resulting in a diamond-like appearance due to the affected branching vessels not having blood supply and the surrounding tissue dying. The same organism causes arthritis in many species, and has been reported to manifest as “bluing” of the redskinned areas of poultry. It is generally a septicemic disease, and the sequelae associated with systemic disease should be considered. Disease in humans: Disease in humans is called erysipeloid and is primarily occupationrelated to owners of pigs, or those who work or care for sick or injured pigs. Inflammatory lesions of the skin, with elevated erythematous edge that spreads circumferentially, are the most common findings. Septicemia is an infrequent complication. Diagnosis: The organism can be cultured from the lesion or blood.

Exotic Small Mammal Care and Husbandry

Prevention and control: Although personal protective measures (gloves, hand washing, etc.) may prevent zoonotic potential, treatment of infected animals can be accomplished with penicillins. A vaccine is available for swine and turkeys, but it should not be used in pets.

Meliodosis Agent: Burkholderia pseudomallei (Pseudomonas pseudomallei) is a motile, gram-negative rod. Reservoir and incidence: This agent is a normal inhabitant of surface soil and water in many tropical areas, especially Southeast Asia. It occurs in wild rodents, goats, pigs, and sheep, and it has been identified in numerous nonhuman primate species. Transmission: Transmission occurs via the bite of an infected rodent, or by inhalation from moist soil or a stagnant water reservoir, or by ingestion of contaminated feeds. Disease in animals: Skin lesions appear with chronic draining, fistulous tracks. Emaciation and multiple abscesses in lung, bone, and viscera also occur. A chronic draining purulent skin lesion should be suspect. Incubation period in a host can be 6 months to 3 years, making identification of the source of transmission extremely difficult. Disease in humans: Clinical disease is not common in humans, but subclinical disease in endemic areas (based on serology) is common. There is a high case fatality rate (80%) for people who do develop clinical signs of multiple abscesses or draining fistulas. Diagnosis: This disease is diagnosed by culture and isolation from lesions.

Tularemia (rabbit fever) Agent: Two strains of Francisella tularensis are agents: Type A strain (F. tularensis var. tularensis) is only seen in North America and causes the disease in humans and rabbits. Type B strain (F. tularensis var. palaearctica) is found worldwide except for Australia and Antarctica (marine animals) and has lower virulence.

Preventive Medicine

Reservoir and incidence: This is a common and often fatal septicemic disease of rabbits, squirrels, muskrats, deer, bull snakes, sheep, wild rodents, cats, and dogs. The major reservoirs in North America include rabbits, ticks, and muskrats. It has also been reported in monkeys at city zoos, most probably infected by wandering rabbits or rodents. Recent reports suggest that tularemia should be considered in cats with a history of ingesting wild prey that manifest signs of malaise, lymphadenopathy, and oral ulcers. Transmission: The handling of tissue from infected animals is the primary means of transmission. Direct contact with skin (it doesn’t have to be a skin lesion) is sufficient for human infection to occur. There have been reported human infections also due to a cat bite, a cat scratch, or a pet monkey bite. The disease may also be transmitted by biting insects, such as ticks or deerflies. Less commonly, it has been transmitted by inhalation, ingestion, and exposure of mucous membranes. Disease in animals: The most typical gross lesions are white-gray foci of necrosis found on surfaces of the spleen, liver, and lymph nodes. Generalized illness and cutaneous hemorrhage has also been reported. Disease in humans: Two forms of this disease exist: the ulceroglandular form (75%–85% of cases), and the typhoidal form (5%–15% of cases). Pleuropulmonary complications develop in 30%–80% of typhoidal cases and 10%– 15% of ulceroglandular cases. Diagnosis: The agents may be cultured, but this requires specialized laboratory equipment and agar (glucose cysteine agar with thiamine or cystine heart agar). Immunofluorescent techniques may be used for agent identification in tissues, and an agglutination titer (must see fourfold rise in titer between acute and convalescent serum) can also serve as a diagnostic tool. Prevention and control: As with many diseases, strong personal protective measures are always worthwhile. Technicians should at a minimum wear gloves while handling poten-

33

tially infected animals or tissues. Controlling ticks is an important aspect of disease management. An experimental vaccine for high-risk personnel does exist in specialized research settings (this agent has been suggested as a potential biological warfare agent; the vaccine is available just in case). Treatment is fairly simple; caught in the early stages, streptomycin or gentamicin is effective at eliminating the agent.

Streptococci There is an overlap of disease-producing streptococci of animals and humans, but generally speaking zoonotic transmission appears rare. Agent:

There are three agents:

1. Gram-positive cocci, many pathogenic species of Streptococcus, including S. pneumoniae, S. pyogenes (Group A), S. suis, and S. (Enterococcus) faecalis. 2. Lancefield serologic Group C organisms produce most disease in pet animals. Only occasionally are Groups A, B, D, and G implicated in animal infections. 3. Most human infection is caused by Lancefield Group A. Groups B, C, D, F, and G can also be pathogenic in humans. Reservoir and incidence: Streptococcus occurs in many species, including calves, monkeys, guinea pigs, rats, and humans. Pet cats and dogs have been implicated in recurrent strep sore throat infections in members of the household. However, if a Group A Streptococcus is found (which is the more common finding), it is highly unlikely that an animal reservoir was involved. Streptococcus suis has been isolated from swine, cattle, cats, and horses; human infections have been reported mostly in western Europe with two cases reported in Canada. Transmission: Fomite transmission may occur, but inhalation is also a common means of transmitting the disease. Disease in animals: Often this disease is inapparent, but it may range from mild respiratory disease to severe pneumonia. Meningoencephalitis has been reported in monkeys (S. pneu-

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moniae). Streptococcus suis causes meningitis, pericarditis, and pneumonia in pigs. Disease in humans: As with animals, this disease is highly variable and may be observed as a sore throat, pneumonia, or other systemic condition such as mastitis or abscessation. When S. suis becomes systemic, generalized septicemia, joint pain, and meningitis may occur. Streptococcus pyogenes (Group A) has resulted in a toxic-shock-like syndrome and necrotizing fasciitis. Diagnosis: Isolation and culture. Prevention and control: The key to preventing this disease is wearing of protective clothing and proper safety equipment when working with animals having the disease. Hand washing after working with any animal is considered a minimum, and this is a case where hand washing is highly effective at preventing incidental transmission.

Pseudomonas Agent: Pseudomonas aeruginosa is a small, motile, gram-negative rod. Reservoir and incidence: Normally, pseudomonas is a saprophytic (not dangerous) organism that is ubiquitous (found many places) in the environment.

Exotic Small Mammal Care and Husbandry

where the abscess has grown to a remarkable size and the animal continues to be “normal.” The medical concern begins when the abscess occurs in a physiologically important area of the body where it may be life threatening— nervous system, liver, kidney—rather than a subcutaneous location (rarely are significant signs observed). Disease in humans: This disease is rare in an immunologically “normal” individual, but immunosuppression or other ongoing diseases may provide the “open door” for a serious, even fatal, infection with pseudomonas. Client education is critical when there are immunosuppressed humans living near or with animals that may have pseudomonas. Diagnosis: Culture and treatment of the affected animal is generally successful. In advanced cases, draining the abscess and treatment of secondary sequelae may be necessary. Prevention and control: Due to the ubiquitous nature of this agent, it is difficult to truly prevent the agent from being in or near animals. The best measure of prevention is a strong program of good animal husbandry and rapid treatment of affected animals with properly selected antibiotics.

Staphylococci Agent:

Transmission: Pets and their human companions may both serve as the disease host. Two outbreaks of Pseudomonas infection within a small mouse colony were linked to the infected human companions. What is curious is that while we clearly recognize pseudomonas in animals and humans, and the same subtypes of the agent are found in both human and animal disease conditions, there has yet to be a single case of documented animal-to-human transmission. It is likely that animal-to-human transmission has occurred, but the ubiquitous nature of this agent makes it difficult to be certain of the incident source. Disease in animals: Often animals carry this agent with no evidence of disease. There are, however, plenty of cases of pseudomonas abscessation, especially of rodents and rabbits,

Staphylococcus spp.

Reservoir and incidence: Normally a saprophytic (not dangerous) organism that is ubiquitous (found many places) in the environment, this agent can be found on all mammals, from the skin to the gastrointestinal tract. Transmission: Because this agent is a commensal for mammals, discussion of transmission is not necessary. It becomes more of a review of the stress factors on the individual that allowed for the development of disease from the individual’s own staphylococcus colonies. As with pseudomonas, while we clearly recognize staphylococcus in animals and humans, there had yet to be a single case of documented animal-to-human transmission. It is likely that animal-to-human transmission has occurred, but the ubiquitous nature of this

Preventive Medicine

agent makes it difficult to be certain of the incident source. Supporting an argument of potential zoonotic transmission, human phage types of S. aureus have caused disease with immune-compromised research rodent colonies. In these same research rodent colonies, human care providers have been found to have seroconverted to the same phage type, thereby supporting an argument for zoonotic transmission of this agent. However, the real potential of zoonotic transmission remains poorly understood. Disease in animals: Often animals carry this agent with no evidence of disease. There are, however, numerous examples of staphylococcus abscessation in rodents and rabbits. The majority of these cases present simply as a “normal” animal with a very large abscess. As with pseudomonas, the medical concern occurs when the abscessation occurs in a physiologically important area of the body where it may be life threatening—nervous system, liver, kidney—rather than a subcutaneous location (rarely are significant signs observed). Disease in humans: This disease is rare in an immunologically “normal” individual, but immunosuppression or other ongoing diseases may provide the “open door” for a serious, even fatal infection. Client education is critical when there are immunosuppressed humans living near or with animals that may have staphylococcus. Diagnosis: Culture and treatment of the affected animal is generally successful. In advanced cases, draining the abscess and treatment of secondary sequellae may be necessary. Prevention and control: Due to the ubiquitous nature of this agent, it is difficult to truly prevent the agent from being in or near animals. The best measure of prevention is a strong program of good animal husbandry and rapid treatment of affected animals with properly selected antibiotics.

Rat bite fever Agent: Gram-negative, pleomorphic bacillus. Two different agents can cause disease:

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1. Streptobacillus moniliformis (Haverhill fever—named after a 1926 outbreak in Haverhill, Massachusetts, attributed to contaminated milk). 2. Spirillum minus (Sodoku). Reservoir and incidence: The agent is present in the oral and respiratory passages of a large number of asymptomatic rodents, especially rats and mice. Incidence of disease, however, appears to be low. Transmission: Generally, human infection comes from close association with infected rodents, usually the bite of an infected rodent. Historically, or in parts of the world where dairy or food sanitation is lacking, infection may also occur via ingestion of contaminated milk or food. Disease in animals: In rats and mice, the infection of an immune-competent animal is inapparent. For conditions where the rodent is diseased, acute, systemic and fatal conditions occur, exhibiting suppurative polyarthritis, swelling, and loss of digits or limbs (for survivors of the disease). Disease in humans: In humans, an acute febrile disease may result following a bite from a rodent. Clinical symptoms include inflammation, lymphadenopathy, and nonspecific signs such as a rash on the extremities (often just the soles and palms). Arthritis has occurred with S. moniliformis. Because the two agents have vastly different incubation periods, the time from potential infection to onset of disease may offer insight into which agent is at fault. Streptobacillus moniliformis only requires hours to 1–3 days for clinical disease. Spirillum minus incubates in the body for 1–6 weeks prior to erupting with clinical disease. In both cases, and in immune-competent individuals, symptoms usually resolve spontaneously, assisted by the appropriate antibiotic. If left untreated, complications may lead to pneumonia, hepatitis, enteritis, and endocarditis. Diagnosis: Culture is the primary method of confirming the disease. Streptobacillus moniliformis requires 10%–20% horse or rabbit serum and reduced oxygen tension. Spirillum

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minus cannot be grown under laboratory conditions; culture may require tissue samples from the infected individual or inoculation into a test rodent with subsequent identification by histology and dark field microscopy. Prevention and control: Proper post-bite treatment of a rodent bite is the best prevention. Extensive washing or scrubbing of the bitten area and application of a topical antibiotic are generally considered effective.

Pasteurellosis Agent: Pasteurella multocida Reservoir and incidence: This agent inhabits the oral cavity and upper respiratory tract of many animals (rabbits, dogs, cats, mice, birds, pigs). Transmission: Infection may occur from an infected animal or via inhalation. One such report noted that a pet owner kissing her dog on the mouth cultured positive for the disease. A subsequent assessment considered the numerous dental caries as being the entry point into her body. Disease in animals: This agent can cause acute pneumonia or septicemic disease in many species. Especially in the rabbit, one may see chronic infection of the upper respiratory tract and the middle ear. Disease in humans: The symptoms and clinical presentation depend upon the development of the disease. Humans may develop septicemia after being bitten by an infected or carrier animal.

Exotic Small Mammal Care and Husbandry

Reservoir and incidence: Bordetella is a common cause of acute respiratory disease in dogs, cats, guinea pigs, rats, rabbits, pigs, horses, monkeys, and sometimes humans. Sometimes called kennel cough, this agent may reside at kennels or animal lodging locations and be spread to new boarders. Transmission: This agent is spread by shedding of respiratory droplets to susceptible animals in close contact or at least near enough for inhalation. Transmission from animals to man has not been reported. Most rabbits and many humans are carriers for bordetella and are the species where bordetella is of greatest significance; one should never house or maintain rabbits and guinea pigs in the same space. In rabbits, the disease is generally inconsequential. In guinea pigs this can be a fatal and rapidly spreading (to other guinea pigs) disease. Disease in animals: Bordetella in animals is an acute respiratory disease, with a hacking cough as the most common presentation. Many of these animals will become carriers of the disease. It is generally not an important disease from the standpoint of being life threatening, but the damage to the client’s “good-will” when retrieving their boarded animal may be significant. In the very young, the aged, ill, or immune-compromised animals, this disease may be life threatening. Disease in humans: Rarely an important disease in humans, it can cause lung abscesses or a whooping-cough-like syndrome.

Prevention and control: The best prevention involves proper treatment of bite wounds with washing and rinsing and the use of effective antibiotics (penicillins, tetracycline, others). When working with potentially infected animals, technicians should wear protective clothing: at a minimum a mask, clothes cover, and gloves.

Prevention and control: A bacterin is available for this agent, but the nasal vaccine is generally considered adequate. In either case, immunity, while strong, is short lived and should be repeated every 6–8 months if animals will be group-housed or if reinfection becomes a potential. Because there have been no zoonotic cases reported, the potential for human infection is low; however, the possibility of transmission by humans to other animals is high. Protective clothing, a face mask, and gloves are recommended.

Bordetellosis

DF-2 and DF-2-like

Agent: Bordetella bronchiseptica, a gramnegative bacillus

Agent: Historically known as Dysgonic Fermenter 2 (DF-2) or DF-2-like organisms, this

Preventive Medicine

group of agents has been renamed Capnocytophaga canimorsus and C. cynodegni, respectively. Reservoir and incidence: Both are found as part of oral flora of normal dogs and cats. The C. cynodegni is closely related to C. canimorsus and causes localized infections following bite wounds but is incapable of causing septicemia like C. canimorsus. Serious C. canimorsus infections in humans are most commonly reported in splenectomized or immunocompromised people, following a bite from dog or cat. More than 40 cases have been reported, many fatal, since first reported in 1976. Transmission: This agent generally requires close contact, a bite, or a scratch from dog (most common), cat, sheep, or cattle. Disease in humans: Capnocytophaga canimorsus infection can lead to cellulitis and overwhelming bacteremia, meningitis, endocarditis, and disseminated intravascular coagulation (DIC). Most serious disease and fatalities have occurred in splenectomized people; however, Capnocytophaga spp. have been associated with infections in both immunocompromised and immunocompetent people. Diagnosis: The diagnosis often occurs through a combination of history, clinical signs, and culture. This organism is very slow growing and may require 8 days or longer of incubation to be visualized. The microscopic examination of the blood smear or buffy coat with Gram’s stain is necessary to detect gramnegative bacilli in neutrophils. Prevention and control: This disease is yet another case in which the technician should be aware of the risk to immune-compromised family members or friends. High-risk individuals may wish to avoid petting or playing with dogs and cats; at a minimum, good hand washing after the interaction has occurred is important. All bite wounds should be treated, but simple antibiotics, even penicillin, are generally effective against this agent. In high-risk individuals, treatment even without signs of infection is recommended.

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Chlamydial diseases Bartonellosis (previously cat scratch disease) Agent: There are four agents: Bartonella henselae [historically associated with cat scratch disease (CSD)], B. quintana (trench fever), B. vinsonii, and B. elizabethae. An indirect fluorescent-antibody (IFA) test for the detection of humoral response to Rochalimaea henselae was developed; its relatively high sensitivity (88%) and specificity (94%) for CSD suggested that R. henselae or a closely related organism may have had an etiologic role. Although a polymerase chain reaction (PCR) assay for Afipia felis showed positive results against specimens from patients with CSD, most investigators believed that R. henselae was the primary etiological agent, with A. felis playing only a minor role. In 1993, convincing evidence was provided to justify reclassification of the four species in the genus Rochalimaea. These four species were united with the genus and named B. henselae, B. quintana, B. vinsonii, and B. elizabethae. This reclassification resulted in the transfer of these organisms from the family Rickettsiaceae to the family Bartonellaceae and removed the family Bartonellaceae from the order Rickettsiales (JAVMA, 1995, p.16). Historically CSD produced a nonfatal and usually mild disease that was also called benign inoculation lymphoreticulosis or nonbacterial regional lymphadenitis. Bartonella spp. are also associated with bacillary angiomatosis, a vasoproliferative tissue reaction seen mainly in immunocompromised individuals, such as AIDS patients or individuals undergoing cancer therapy. Bartonella spp. have also been associated with several other distinct clinical syndromes in people, including bacillary peliosis hepatitis, relapsing fever, endocarditis, retinitis, and pulmonary granulomas. Reservoir and incidence: Bartonella henselae bacteremia has been documented in 25%–41% of healthy cats. Serologic surveys show an overall prevalence of 28% in the United States, lower in the Midwest and Great Plains and higher in the Southeast. High seroprevalence correlated with warm, humid climates. The Centers for Disease Control and Prevention estimates 22,000 cases of CSD

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annually in the United States [(MMWR, 1995 (43:49, p. 915)). Transmission: Human cases of CSD have been strongly associated with cats less than 1 year old, a history of a bite or scratch, contact with fleas. Bartonella henselae has been isolated from fleas obtaining blood meals from naturally infected cats, but vector competence has not been reported. Disease in humans: A primary lesion, most common on the neck or extremities, will develop in 50% of cases and appears approximately 10 days after a bite or scratch. A pustule persists for 1–2 weeks; 10–14 days after the lesion appears, lymphadenopathy develops and usually regresses within 6 weeks. Thirty to fifty percent of the enlarged nodes become suppurative. Of the approximately 65% who develop systemic illness, fever and malaise are the symptoms most often noted. Approximately 10% of previously recognized CSD cases were accompanied by tonsillitis, encephalitis, cerebral arteritis, myelitis, granulomatous hepatitis, splenitis, osteolysis, pneumonia, pleural effusion, and thrombocytopenic purpura. The disease is usually benign and most patients recover spontaneously without sequelae within 2 months. Many unrecognized cases probably occur. Disease appears to confer lifelong immunity. Diagnosis: 1. Isolation of organism 2. PCR 3. Seroconversion [IFA or enzyme-linked immunosorbent assay (ELISA)] with acute disease Prevention and control: 1. Education 2. Wash hands after handling cat 3. Wash cuts and scratches promptly and do not allow cat to lick an open wound

Rickettsial diseases Ehrlichiosis Agent: Ehrlichia chaffeensis.

Exotic Small Mammal Care and Husbandry

Reservoir and incidence: The existence of a reservoir other than the tick is unknown. Because of the similarity between the clinical presentation of E. canis infection in dogs and E. chaffeensis infection in people, and the serologic cross-reaction between the two species, E. canis was considered the etiologic agent of human ehrlichiosis in North America until E. chaffeensis was isolated and characterized in the early 1990s. Ehrlichia canis is not a human pathogen. Transmission: Transmission is via tick bite— the Lone Star tick, Amblyomma americanum, which has a geographic and seasonal distribution compatible with the epidemiology of monocytic ehrlichiosis. Disease in humans: human pathogen.

Ehrlichia canis is not a

Diagnosis: The nonspecific signs and symptoms compatible with ehrlichiosis, added to a history of tick bite or tick contact, may provide strong suspicion. Indirect IFA showing fourfold rise in antibody titer or PCR can be used to confirm the infection. Prevention and control: This disease is best prevented by control of the tick vectors.

Rocky Mountain spotted fever (RMSF) Agent:

Rickettsia rickettsii

Reservoir and incidence: Dogs, wild rodents, and rabbits may each serve as a reservoir host for this disease, which is reported most commonly from the continental United States. The name for this disease comes from its index reports of tick fever in the Rocky Mountain region; however, less than 1% of the cases of the disease occur in this area. Most cases of Rocky Mountain spotted fever (RMSF) occur in the south Atlantic, south central, and southeast states. Twothirds of all human cases are reported in children. Transmission: Distribution of RMSF centers around three vector ticks: Dermacentor andersoni (American wood tick), D. variabilis (American dog tick), and Amblyomma ameri-

Preventive Medicine

canum (Lone Star tick). Ticks are both reservoir and vector, transmitting the organism transovarially. Direct transmission from dogs to humans does not occur, and dogs are unlikely reservoirs as they develop a low rickettsemia. Disease in animals: The signs are highly variable, but they include fever, vomiting, diarrhea, depression, and dependent edema. Ocular lesions are common in dogs and include subconjunctival hemorrhage, hyphema, anterior uveitis, retinal petechiae, and focal retinal edema. Disease in humans: Symptoms are multisystemic with fever, headache, myalgia, maculopapular rash (12%), shock, coma, and death (5%–10%). Diagnosis: Serology is accurate. However, it takes several days using the Weil–Felix testing (agglutination of sera with Proteus spp. antigens), and it is only accurate after the second week of illness. Complement fixation and microimmunofluorescent tests are also used. Direct FA of infected tissues appears a promising modality for the future. Treatment, prevention, and control: Treatment of the active disease consists of tetracycline or chloramphenicol. Chloramphenicol may thwart the increase in antibody concentration in dogs and interferes with serodiagnosis. The most effective measure is the control of ticks on newly arrived animals. Technicians should note that after removal from the animal, the ticks remain infected. Proper removal and disposal with appropriate precautions is required.

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Transmission: The rodent mite, Allodermanyssus sanguineus, transmits the infectious agent to mice and humans. Disease in animals: General malaise and signs of “not feeling well.” Animals may die, but often it is from secondary infections or other causes. Disease in humans: The disease causes chills, fever, and rashes. Usually it is self-limiting, lasting about 1 week. Prevention and control: The key for this disease is to prevent wild mice from accessing the home or the areas where pets are held. Although mites are the vector for the disease, a good mite control program for pet animals is also worthwhile, especially in areas where urban vermin infestation is a potential.

Murine typhus Agent:

Rickettsia typhi (R. mooseri)

Reservoir and incidence: This is a natural pathogen of rats and mice. Other mammals that may serve as a reservoir include cats and their ectoparasites. Outbreaks continue to occur in the United States, and more commonly along the southwest border states. Transmission: The organism is transmitted by fleas (Xenopsylla cheopis, Nasopsyllus fasciatus). Infected flea bites will transmit the disease to either rodents or humans. Disease in animals: Signs would be expected to be similar to humans, but recording chills is difficult, and capturing a fever is dependent upon the time of assessment. Rashes may be the only indication of a problem.

Rickettsial pox Agent: Rickettsia akari Reservoir and incidence: The house mouse is the reservoir host. The disease is most commonly seen in rodent-infested urban dwellings (e.g., New York City and other eastern US cities). Rats and moles can also harbor the organism. Pet rodents may also become infected, but usually through association with vermin-infested dwellings.

Disease in humans: In humans, symptoms include chills, fever, and rash. These are usually self-limiting, lasting only a few days to weeks. Prevention and control: Similar to other conditions, the key is controlling the reservoir and the vectors. In endemic areas, eliminating fleas and preventing access of rats into the house or areas where pets are maintained is necessary to prevent infection.

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Typhuslike (unnamed) disease Agent: Rickettsia felis Reservoir and incidence: This is a “new” rickettsial disease identified by comparison of 16S rRNA and 17-kDa protein gene segment comparisons. In select areas such as southern California and Texas, the classic rat–flea–rat cycle of R. typhi has been replaced by a peridomestic animal cycle involving free-ranging cats, dogs, and opossums and their fleas. Rickettsia felis was identified from the blood of a hospitalized febrile patient and from the patient’s fleas in the course of epidemiologic investigations. Rickettsia felis has also been isolated from cat fleas.

Exotic Small Mammal Care and Husbandry

M. canis (pathogen for dogs) has been isolated from the throat of a pet dog and from each human member of the household. M. fermitans (incognitus) (human pathogen), commonly associated with genital disease, has been suggested to be a cofactor for HIV infections but certainly is a common “opportunistic pathogen” in HIV patients. It remains unclear whether actual infection with clinical disease can result from such colonization. On rare occasions, veterinarians or veterinary technicians may contract mycoplasma while treating infected pets (e.g., cat abscess).

FUNGAL INFECTIONS

Transmission: This disease may be transmitted by fleas (Xenopsylla cheopis, Nasopsyllus fasciatus) to other animals or humans.

Dermatomycosis (ringworm)

Disease in animals: Signs would be expected to be similar to humans, but recording chills is difficult, and capturing a fever is dependent upon the time of assessment. Rashes may be the only indication of a problem.

1. Geophilic—inhabit soil 2. Zoophilic—parasitic on animals 3. Anthropophilic—primarily infect humans

Disease in humans: The symptoms in humans are the typical typhuslike symptoms of chills, fever, and rash. Prevention and control: Similar to other conditions, the key is controlling the reservoir and the vectors. In endemic areas, eliminating fleas from pet cats and preventing access of infested cats into the house or areas where pets or humans live is necessary to prevent infection.

Mycoplasma infections Mycoplasma Agent: Mycoplasmas lack a cell wall and are the smallest known organisms capable of freeliving existence. They are believed to be relatively host specific, but mycoplasmas that cause disease in lower animals have been isolated from man, for example: Mycoplasma arthritidis (rodent pathogen) has been isolated from the human genital tract, synovial fluid, bone marrow, and lymph nodes.

Agent: Ringworm agents are classified as follows:

All of these can produce disease in humans and animals. Ringworm agents are also grouped in three genera: 1. Microsporum 2. Trichophyton 3. Epidermophyton Reservoir and incidence: Exposure to reservoir hosts harboring different dermatophytes determines the type and incidence of infection in humans. Trichophyton mentagrophytes is most commonly transmitted to humans from rodents (dogs are frequent carriers); M. canis from cats (dogs are also frequent carriers); T. verrucosum from cattle; and M. gypseum from dogs and rodents (occasionally cats). Transmission: Direct or indirect contact with asymptomatic animals or with skin lesions of infected animals is the primary mode of transmission. Contaminated bedding and diagnostic or care equipment may also serve as fomites for disease transmission. Fungi in air, in dust, or on surfaces of a room provide long-term con-

Preventive Medicine

cerns for reintroduction of the disease (spores persist on contaminated surfaces). Disease in animals: In rodents and cats, the disease is often asymptomatic and not recognized until people are affected. Dogs often show classic skin lesions. Disease in humans: While usually self-limiting, the human may have mild scaling, redness, and occasionally vesicles or fissures. There will be thickening and discoloring of nails, and there may develop circular lesions that clear in the center forming a ring. Fungal infections in humans are categorized as to the location on the body: 1. Tinea capitis—scalp and hair 2. Tinea corporis—body [extremities (arms and hands) are most often affected in infections acquired from animals]. 3. Tinea pedis—foot 4. Tinea unguim—nails Diagnosis: KOH mount of skin scrapings remains a tried and true method. Fungal cultures may serve as definitive diagnosis. Treatment: A variety of antifungals, even dilute sodium hypochlorite (Clorox) or 2% iodide wash, may be effective in eliminating the disease. Prevention and control: All newly received pets should be screened by closely inspecting all body surfaces for hair loss, patchiness, or rashes. Routine sanitation of the environment and caging should serve to prevent contamination. Technicians should wear gloves and protective clothing when treating affected animals. VIRAL DISEASE

Hemorrhagic fever with renal syndrome (HFRS) Agent: The Bunyaviridae family, Hantavirus genus, includes four distinct groups of Hantaan-related viruses. Reservoir and incidence: Recognized originally in troops serving in the Korean War,

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this virus was named Hantaan after a river in the endemic area of Korea where it was found. There are five hosts (all rodents) of this virus: Apodemus sp.—striped field mouse Rattus norvegicus and R. rattus—rats (both may be pets) Microtus pennsylvanicus—meadow vole Peromyscus leucopus—white-footed mouse Clethriomys glareolus—bank vole Disease in animals: This is a chronic, asymptomatic infection. The virus is shed for extended periods in body fluids. Disease in humans: In the “renal form” of the disease, after a 13- to 22-day incubation period, clinical symptoms of high fever, myalgia, headache, lumbar pain, diarrhea, nausea, vomiting, nephritis, hemorrhage, and shock occur. Mortality may reach 10%. Transmission: This disease is aerosolized from urine, feces, or respiratory secretions of infected rodents. There have been unconfirmed reports of transmission by rodent bite. It is spread horizontally between rodents by saliva. Vertical transmission is thought not to occur. Person-to-person transmission is thought not to occur. Arthropods do not serve as important vectors. Diagnosis: Diagnosis can be based upon serology using indirect immunofluoresence, HI to further determine type of hantavirus, and virus isolation. Prevention and control: Unless wild-caught rodents are being held as pets, there is little risk of this disease. Education and general sanitation that discourages rodent harborage and removes buildup of dust and debris are effective control measures.

Lymphocytic choriomeningitis (LCM) Agent:

Arenavirus

Reservoir and incidence: Wild mice (Mus musculus) of the United States, Asia, Africa, and Europe. The virus has not been isolated from mice in Australia. Wild mice will usually be the index case that may infect pets or

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humans. Of many latent viruses present in mice, only the lymphocytic choriomeningitis (LCM) virus naturally infects humans. The LCM virus can easily be transmitted from animals to humans. This virus was first isolated by Armstrong and Lillie during investigation of a St. Louis encephalitis outbreak in 1933. Mice and hamsters are the only species in which long-term, asymptomatic infection is known to exist. There have been over 200 documented cases associated with pet hamsters in the United States.

Exotic Small Mammal Care and Husbandry

Prevention and control: Infection can be prevented by keeping wild mice out of homes and areas where animals are kept and by controlling ectoparasites and roaches. Technicians should use protective clothing and proper care when handling infected animals or tissues. Basic hand washing is an important step to prevent personal infection.

BITES AND SCRATCHES

Bites Transmission: Humans can be infected with LCM virus directly from feces or urine of mice or hamsters, or indirectly by inhaling the dried excreta carried on aerosolized dust originating from the animal cages or rooms. Technicians may become infected by improper handling of infected murine tissues or being bitten by infected mice. Disease in animals: Acute disease and death, runting, nonspecific signs, or asymptomatic mice all occur. Most mice will recover but become persistent tolerant infection (PTI) spreaders. These animals have no antibody response, making it very difficult to diagnose by common methods. Mice that are congenitally infected are normal at birth and appear normal for most of their life span, and they consistently shed virus in the blood, tissues, and urine. A rudimentary but accurate assessment tool is the production of characteristic convulsive seizures that can be produced in LCM mice by picking them up by the base of the tail and twirling them. This assessment should be performed carefully so as to not injure the animal. Disease in humans: The signs and symptoms can vary dramatically, from a mild flulike syndrome with or without involvement of the CNS, up to a fatal meningioencephalitis. A small number of patients will be hospitalized for prolonged periods and may experience debilitating, chronic sequelae, including fatigue, headache, and depression. Diagnosis: A variety of tests may be used for diagnosis, including IFA, rising antibody titers, and virus isolation.

Health authorities report that more than 1 million people are bitten by dogs each year; however, it is estimated that only half of all bites are reported: Dogs—84% Cats—10% Rodents—4% Skunks and foxes—1% Other (small mammal pets)—1% It is estimated that more than 43,000 people are bitten by rats and mice in the United States each year. Bites cause pain, anxiety, wound disfigurement, and wound infections. Many organisms are capable of infecting animal bite wounds, including Pasteurella spp., V-hemolytic Streptococcus, Staphylococcus aureus, Bacteroides, Fusobacterium, Capnocytophaga canimorsus (previously DF-2), Clostridium tetani, Streptobacillus moniliformis, and Spirillum minus and have been previously discussed. Pasteurella multocida may be responsible for up to 50% and 90% of infections from dog and cat bite wounds, respectively. Treatment: There are specific steps technicians should follow for treatment of bite wounds: 1. Maintain records of all bites and scratches in the animal facility. 2. Notify a physician. The veterinary hospital should have an occupational medicine physician who understands the problems associated with animal handling and is informed about zoonotic diseases. 3. Clean the wound properly, using lots of water, soaps, and disinfecting agents.

Preventive Medicine

Allergic sensitivities Allergic skin and respiratory reactions are quite common in people who have rodent pets and personnel who work closely with rodents. Hypersensitivity reactions in response to animals include the following: a. b. c. d. e. f. g.

Nasal congestion Runny nose Sneezing Itching of eyes Angioedema Asthma A variety of skin manifestations (localized urticaria and eczema)

43

use exhaust hoods (for treatment or surgical procedures), filter tops or closed bags for dirty bedding, and facility clothing, masks, and respirators. An important concept of protecting one’s self and family is to remove all clothing worn while working at the veterinary hospital and launder that clothing at the hospital rather than taking it home to be laundered (and thereby exposing one’s family and pets to potential disease agents).

PARASITIC INFECTIONS AND INFESTATIONS

Toxoplasmosis Almost any animal can cause an allergic sensitivity. Maximal allergenic activity in humans resulted from the albumin fraction of pelt extracts from rats, mice, and rabbits. The fraction of guinea pig extract with maximum allergic activity seems to be a prealbumin. Two major allergens in mouse serum, skin, and urine have been identified. The major urinary protein complex in rodents (especially rat and mouse) is an extremely high allergenic agent. The mechanism of transport involves drying of the rodent urine and adherence of the urine protein to dust or bedding particles, which become airborne and are then inhaled. Diagnosis: Diagnosis of acquired allergies may require a history of animal relationship (pets at home plus animals worked with in the veterinary hospital), a physical exam, pulmonary function tests, skin testing, and laboratory tests [CBC, immunoglobulins and IgE antibody specific to one allergen as measured by the RAST (radio-allergosorbent test) as well as nasal smears for eosinophilia and serum precipitants to specific allergens]. Treatment, prevention, and control: In some cases, pharmacologic treatment is the best approach, but allergen immunotherapy, complete avoidance of the antigen, and reducing exposure to the offending antigen are critically important. Steps veterinary technicians may take to improve their ability to work with animals include the following: reduce the direct animal contact time, increase room ventilation,

Agent: The Toxoplasma gondii organism is 4–7 microns long and 2–4 microns wide. It belongs to the subphylum Apicocomplexa, family Eimeriidae. Reservoir and incidence: Infection in humans and lower animals is widespread. An estimated 500 million humans have been infected with the organism, and close to 40% of adults in the United States have antibodies to T. gondii. Serologic surveys in the United States using the Sabin–Feldman dye test have demonstrated T. gondii infection in 30%–80% of cats. The significance of this finding is that, presumably, all serologically positive cats have shed Toxoplasma oocysts and could re-shed organisms during reinfection or reactivation. Although this text does not include cats as a discussed species, this is a disease that involves cats but causes disease in rodents and humans. The life cycle of this organism begins with a definitive host (sexual reproduction and shedding of oocysts). The domestic cat predominates as the reservoir for zoonotic transmission in the home. Intermediate hosts include mice, rats, hamsters, guinea pigs, other rodents, rabbits, and many other species. Transmission: For pets, dried cat fecal matter is sufficient to result in an infection. For humans, consuming meat containing cysts or tachyzoites, or contamination of the hands while cleaning litter pans and subsequent ingestion of oocysts results in human infestation. Because oocysts become infective only after 2–3 days of sporulation, cleaning of the litter

44

pan daily will prevent the development of infective oocysts. Disease in animals: Most postnatally acquired infections in cats are asymptomatic. When infected, cats shed for 1–2 weeks, during which time this becomes a public health hazard, especially to pregnant women. Oocyst shedding is reactivated by induction of hypercorticism or superinfection with other feline microorganisms. Disease in humans: Although the disease is very common in humans, clinical disease is of low incidence and occurs only sporadically. Postnatal infection is less severe and commonly presents as a generalized lymphadenopathy that may resolve without treatment in a few weeks. Congenital infection (infection of the infant during pregnancy) may result in systemic disease with severe neuropathological changes. Rarely, serious ocular or systemic toxoplasmosis can be acquired by older individuals or reactivated in immunocompromised individuals. At any age, clinical symptoms may include fever, skin eruption, malaise, myalgia, arthralgia, cervical lymphadenopathy, pneumonia, myocarditis, meningoencephalitis, and chorioretinitis. Diagnosis: Serology, isolation, microscopic demonstration of organisms in smear or section, and demonstration of oocyst are the most common methods to diagnose the disease. Paired serum samples taken one or more weeks apart may also be evaluated by the following: a. IFA—serial titers of suspected infections b. Sabin-Feldman dye test—most sensitive test, but not readily available c. IHA—for screening, but not definitive because can be negative early in disease d. ELISA While serology of humans is useful, serology in cats is not useful because either a seropositive or seronegative cat could potentially shed oocysts at a later time. Prevention and control: Technicians are key for assuring effective prevention. The answer? Education, education, education. Recognizing

Exotic Small Mammal Care and Husbandry

the significant impact of disease upon the unborn, the immunocompromised, and the aged may require particular protections or procedures to assure their health and safety. Pet owners should carefully control their cat’s diet, feeding only known items and preventing the consumption dead rodents. Rigorous sanitation of the cat’s living space is effective, especially if litter pans are cleaned daily (because oocysts are not infective for 2–3 days after the fecal matter is dropped in the litter pan). Veterinary technicians and others should wear gloves when cleaning sick or injured animals (because subsequent stress such as another disease can cause a recurrence of oocyst excretion in cats). By all means, be sure to wash your hands vigorously prior to eating, and avoid rare (or raw) meat, especially pork or mutton. Cooking to greater than 65 °C, or until color changes to light tan, is sufficient to kill oocysts. Lastly, pregnant women should avoid contact with cat feces and should avoid working in soil or gardens that could be contaminated by cats, etc.

Pneumocystis carinii Agent: Pneumocystis carinii is a protozoan parasite that occurs worldwide and causes Pneumocystic pneumonia. It is an extracellular organism that some scientists believe is a distinct organism from animals to humans. The taxonomy is uncertain. Reservoir and incidence: All rodents, rabbits, and numerous other animals may harbor this agent. The incidence is unknown due to the high variability of the agent in species and location. Transmission: Although the contagious pattern suggests patient-to-patient transmission in humans and acquisition from the environment are the primary routes of infection, recognizing the high degree of similarity in the agents found in animals and humans, zoonotic transmission cannot be ruled out. Disease in animals: Respiratory disease has been reported that clinically is similar to that reported in humans. Disease in humans: This disease is more often observed in infants or debilitated individuals

Preventive Medicine

45

with neoplasia, poor nutrition, or immunodeficiency. It is frequently fatal in humans, resulting in a diffuse desquamative alveolitis as the parenchyma fills with edematous and foamy fluid containing numerous parasites.

Disease in animals: In animals, severe watery diarrhea occurs; however, the disease is often inapparent in guinea pigs. Two strains of Cryptosporidium with different host ranges parasitize the intestinal tract of guinea pigs.

Treatment: Trimethoprim and sulfamethoxazole appear to be effective at controlling the disease (it is not possible to fully eliminate the organisms).

Disease in humans: Most recorded cases in humans have occurred in immunodeficient individuals, but the organism is capable of causing disease by itself. Prognosis for immunologically compromised individuals is grave because effective chemotherapeutic means of eliminating the parasite are not available. Usually the signs present after a 4- to 12-day incubation period with flulike disease including fever, malaise, nausea, and protracted watery diarrhea. It is usually self-limiting, with complications in those with impaired immune response.

Cryptosporidiosis Agent: Extracellular protozoal organisms, similar to coccidia, in the genus Cryptosporidium with 19 species, suborder Eimeriorina are the agent for cryptosporidiosis. The taxonomy of species is somewhat controversial but is considered to be infective across species lines. Reservoir and incidence: This agent may be found in guinea pigs, mice, rats, rabbits, and many other species. Among animals, dogs appear to be resistant to infection, although they have been found to be serologically positive. Transmission: No intermediate host is required, thus infection can occur by ingestion of infective sporulated oocysts. In contrast to other coccidians, these oocysts are sporulated and infectious at the time of excretion. In fact, the organism can exist within the host, causing immediate reinfection. Most commonly, the oocyst localizes in the small and large intestines but it may also be associated with invasion of the stomach, bile ducts, pancreatic ducts, and gallbladder. Cryptosporidium parvum commonly parasitizes the intestinal tract of humans. Cryptosporidium muris infects the stomach of mice and is thought to be more host- and tissue-specific than C. parvum, although it has been found in the gastric glands of adult cattle as well. Although strains of Cryptosporidium that are predominant in calves and humans are cross transmissible and can infect various other host species, isolates from guinea pigs and calves probably have different host ranges. The isolate of Cryptosporidium sp. from chickens is not infectious for mice. There is no evidence that C. muris can infect human beings.

Diagnosis: The organism may be identified by H&E staining of intestinal specimens taken within 1–2 hours of death of the animals. The small size of the organisms, 4–6 microns, and low excretion rates in infected individuals make detection difficult. Centrifugation of fecal flotation in a high-gravity salt or sugar solution, and smears of the supernate stained with Giemsa, PAS, Kinyouns, or Ziehl–Nielsen aid in identification of oocysts and maximizes detecting the organism. Phase contrast aids detection with coverslip flotations. Formalin fixation is recommended due to the potential of fecal–oral transmission. Prevention and control: A 5% ammonia or 10% formalin solution will kill oocysts after 18 hours, or heating of contaminated materials to 65 °C for 30 minutes. Freezing will also kill oocysts. No treatment is known to eliminate it in the host. Treatment consists of supportive therapy. The organism is refractory to antibiotic therapy. Cages or pens should be thoroughly cleaned with ammonia solution and allowed to dry for several days between animals. Immunosuppressed individuals should not work with or have as pets infected animals.

Helminth infections Many of the helminth parasites common to both animals and humans have an indirect life cycle that can be easily interrupted, but if left

46

unchecked will become zoonotic. Parasites with a direct life cycle do not require an intermediate host and therefore may cause infection more readily. Proper quarantine, surveillance, and treatment to decrease endoparasitic burden, routine sanitation to eliminate parasitic ova before they can become infective, and education of pet owners on standard hygiene practices are measures that can be taken to prevent transmission of these diseases.

Nematodes Capillariasis Agent: Capillaria hepatica (capillary liver worm). Reservoir and incidence: These parasites have a worldwide distribution with selected locations having a high prevalence. They are primarily a parasite of rodents, but other rodent and mammalian species may be affected. Peromyscus maniculatus and Clethrionomys gapperi are the major hosts in North America. Transmission: In nature, rats and mice are usually infected by eating meat containing the parasite. They then seed the environment with eggs passed in their feces, which are ingested by other animals or humans. When eggs are ingested by another animal or human host, the parasite penetrates the intestinal wall and migrates to the liver via portal circulation. Disease in animals: With heavy infections the animal may become emaciated, jaundiced, and show ascites. Parasites mature and deposit eggs in liver tissue. Disease in humans: Subclinical infection is suspected in humans, as in rodents. When not treated, the infection may lead to death. More commonly, fever, hepatomegaly, eosinophilia, leukocytosis, and hypergammaglobulinemia occur.

Exotic Small Mammal Care and Husbandry

cooking of foods and water when living in nature, preventing pica, and other sanitary practices.

Hymenolepis diminuta Agent: Hymenolepis diminuta is the common tapeworm of rats. Size varies from 100 to 600 mm. Hosts: This parasite is found in the small intestine of rats, mice, humans, and hamsters. Insects that serve as obligatory intermediate hosts include beetles, cockroaches, earwigs, fleas, and mealworms. Occurrence: Historically a common parasite, its occurrence is rare due to improved sanitation and vermin control. Distribution: It is found in Africa, South America, the Caribbean, Italy, Japan, the United States, and the countries of the former USSR. Transmission: The transmission is simple: rat—insect—rat or rat—insect—human. Rats ingest various arthropod intermediate hosts. Humans become infected by accidental ingestion of the cysticercoid larvae that are present in infected intermediate arthropod hosts in contaminated grain. This parasite is rare in the mouse due to faster intestinal emptying time in mice. Disease in animals: This disease produces no symptoms or pathological lesion. Disease in humans: There is no known serious pathology in humans. Diagnosis: Diagnosis examination.

is

made

by

stool

Prevention and control: Elimination of insects will prevent the continuation of the life cycle and development of the infective cysts.

Diagnosis: A liver biopsy, history of living in nature or unsanitary conditions, and clinical symptoms collectively offer the diagnosis.

Hymenolepis nana

Prevention and control: The key to preventing this disease is health education, boiling or

Hosts: Mice, rats, and occasionally humans may serve as host for this parasite. The parasite

Agent:

Hymenolepis nana (dwarf tapeworm)

Preventive Medicine

measures 5–90 mm long, with its size inversely proportional to the number of worms in the host. A distinguishing feature of the mature segment is the “three testes,” one on the left and two on the right side of the median line. Reservoir and incidence: This parasite is cosmopolitan in distribution, just as common in cold as in warm climates. Infection rates are higher in children than in adults, and more common in institutions such as children’s homes and orphanages, than in children who live in single-family homes. Transmission: The parasite uses either a direct fecal–oral cycle or indirect ingestion from accidental ingestion of infected insects. Human infection is caused by ingestion of H. nana eggs, or by ingestion of infected intermediate hosts such as fleas, mealworms, beetles, or cockroaches. Although the more common life cycle is direct, insects that may serve as intermediate hosts include Ctenocephalides canis, X. cheops, P. irritans, and B. germanica. The eggs are infective when passed from the body of the host but do not survive long outside the body. Autoinfection can occur from eggs hatching within the intestine. Disease in animals: There is no serious pathology or symptoms associated with this parasite in animals. The parasite does consume carbohydrate from the intestine of the host and therefore may compete for nutrition, including vitamins and amino acids. Young rodents are more resistant than older rodents, due to the short length of the intestine in young mice. Autoinfection is responsible for persistent infection in murine and human hosts. Disease in humans: Symptoms depend on the number of worms in the body. Metabolic wastes from the parasite can be absorbed and

47

may cause toxemia in humans. Considerable irritation of the small intestinal mucosa may also occur with large numbers of worms. Some human patients may experience headaches, diarrhea, anal itching, anorexia, and convulsions. Autoinfection may occur and the disease may last for as long as 22 months. Diagnosis: This parasite is easily observed in a fecal flotation (segments are not passed in feces, look for eggs only). Prevention and control: A variety of treatments are available for this parasite, but to prevent autoinfection, treatments should be repeated or extended. Treatment intervals should not exceed 7 days. Additional supportive measures include good personal hygiene, effective use of protective clothing and gloves, strong vermin control, and protection of feed grain from grain beetles.

REFERENCES Centers for Disease Control and Prevention (CDC). 1994. Summary of Notifiable Diseases, United States, 1994. MMWR 1995 43(49). Centers for Disease Control and Prevention (CDC). 1996. Summary of Notifiable Diseases, United States, 1996. MMWR 1997 45(53). Available at www.cdc.gov/ncphi/disss/nndss/ annsum (accessed September 9, 2009). JAVMA. 1995. Zoonosis Updates. J. American Veterinary Medical Association 207. Margileth, A.M., and Hayden, G.F. 1993. Cat scratch disease – From feline affection to human infection. New England Journal of Medicine 329:53–54. Small Animal Compendium. 1993. Small Animal Compendium for Continuing Education 15:3, March 1993.

Rabbits

4

Rabbits are generally docile and engaging animals. Their quiet nature and relatively simple housing and husbandry requirements have contributed to their increasing popularity as pets. COMMON BREEDS

Currently more than 45 breeds are recognized by the American Rabbit Breeders Association, all derived from the domestic rabbit, Oryctolagus cuniculus. Many rabbit breeds have been developed for physical traits such as body conformation and fur characteristics. A complete index of recognized breeds is available on the website of the American Rabbit Breeders Association, Inc., at www.arba.net. BASIC ANATOMY AND PHYSIOLOGY

Rabbits have a large muscle mass compared to their skeleton. The muscle mass comprises greater than 50% of the body weight and the skeleton only 7%–8% (Donnelly, 2004). This feature makes them predisposed to fractures of the limbs or vertebrae if not properly restrained during handling. Rabbits can be removed from a cage by grasping the loose skin over the shoulders with one hand to lift the rabbit from the cage while supporting the hindquarters by placing a hand under the rump. They can be carried by tucking the head into one arm while supporting the rear in the other (Fig. 4.1). This will prevent the rabbit from kicking its powerful legs and causing injury to its back.

Fig. 4.1 Proper rabbit manual restraint. For color detail, please see color plate section.

Rabbits’ fur is very fine and their skin very delicate. Extreme care should be taken, using fine clipper blades, when clipping hair for surgery to avoid tearing the skin. Their feet are covered with coarse fur instead of footpads. Ulcerative pododermatitis, commonly called sore hocks, is frequently encountered in overweight rabbits housed on wire cage flooring. Male and female rabbits have well-developed scent glands, including the chin glands, the anal glands, and the inguinal glands. Male rabbits mark their territory more aggressively than females, and dominant animals of both sexes mark more than submissive animals. Rabbits have a very well-developed sense of smell. Breathing is characterized by twitching the nostrils to direct the flow of air over the turbinates where olfactory cells are located. 49

50

Exotic Small Mammal Care and Husbandry

Table 4.1 Basic biological parameters. Body weight

Adult male: 2–5 kg Adult female: 2–6 kg Birth weight: 30–60 g

Body temperature

37.8 °C–39.4 °C (100 °F–103 °F)

Reproductive data

Sexual maturity Female: 4–9 months Male: 6–10 months Estrous cycle: 15–17 days Ovulation: induced Gestation length: 29–35 days Litter size: 4–10 Weaning age: 4–6 weeks

Life span (captivity)

5–7 years

Heart rate

130–325 beats per minute

Respiratory rate

32–60 breaths per minute

Food intake

50 g/kg/day

Water intake

50–100 mL/kg/day

From: Bradley (2001); Carpenter (2005); Donnelly (2004); Suckow and Douglas (1997).

Because rabbits are obligate nasal breathers, open-mouthed breathing is generally considered a poor prognostic indicator (Donnelly, 2004). The teeth of rabbits grow continuously throughout their lives. The dental formula is 2(2/1 incisors, 0/0 canines, 3/2 premolars, 3/3 molars) = 28. The two lower incisors rest between the four large upper incisors and peg teeth. Incisor malocclusion is seen commonly in pet rabbits, particularly with mandibular prognathism (Fig. 4.2). The relatively small mouth opening makes endotracheal intubation in rabbits challenging. The gastrointestinal tract of rabbits is very large and contains a coiled cecum that can hold up to 40% of the ingesta. The colon regulates the formation of hard and soft fecal pellets. Rabbits consume soft pellets, or cecotrophs, directly from the anus for nutritional benefit, primarily protein and B vitamins (Suckow et al., 2002). Table 4.1 gives the basic biological parameters of rabbits. Urine is a major route of calcium excretion in rabbits, with normal urine having a cloudy appearance ranging to a thick and creamy con-

Fig. 4.2 Mandibular prognathism and malocclusion. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.) For color detail, please see color plate section.

sistency due to the high concentration of ammonium magnesium phosphate and calcium carbonate monohydrate precipitates. The color can vary from yellow to reddish, often mistaken for blood, and is somewhat dependent upon the diet. (See section “Clinical techniques,” Table 4.3.) REPRODUCTION AND SEXING

Sex determination is performed by gently applying pressure above the genitalia. In males, the penis will evert and appears like a rounded protrusion with a circular opening (urethra) at the distal tip. The vulva has a more slit-like appearance (Bradley, 2001) (Fig. 4.3a). Males have two scrotal sacs cranial to the penis (Fig. 4.3b). Male rabbits have open inguinal rings and can retract their testes. Puberty generally occurs between 5 and 8 months of age in larger breeds and between 4 and 5 months in smaller breeds. The reproductive life of a doe generally lasts up to 3 years, though bucks will remain useful as breeders for 5–6 years. Spaying and neutering pet rabbits has many benefits. Neutered males and spayed females tend to mark their territory less and be less aggressive. Spaying females can prevent reproductive neoplasia. Uterine adenocarcinoma is reported to have a high incidence of up to 80% in certain breeds (Antinoff, 1999).

Rabbits

a

51

b

Fig. 4.3a External genitalia of a female rabbit. For color detail, please see color plate section.

Fig. 4.3b External genitalia of a male rabbit. For color detail, please see color plate section.

The breeding cycle in rabbits is influenced by day length and environmental temperature, with the highest conception rates in the spring. Receptive does exhibit lordosis (flattening of the back, raising of the pelvis) in response to attempts by a buck to mount. The gestation period is approximately 30–32 days. In the last days of gestation, mammary gland development occurs and does can be observed pulling hair from the abdomen to make a nest. Kits are usually born in the early morning. Litter sizes vary with breed, with smaller breeds producing 4–5 kits, and large breeds producing 8–12 kits. Kits typically nurse only once a day for 3–5 minutes, in which time they can drink up to 20% of their body weight. Solid food can be consumed by 3 weeks of age, and kits can be weaned at 5–8 weeks of age. There are several published formulas available for hand-rearing rabbits if needed in cases of orphaned kits or poor maternal care. Combinations of KMR Kitten Milk Replacer and Multi-Milk powder (PetAg, Hampshire, IL, www.petag.com) will provide appropriate

nutritional support for neonates. Neonates should be fed three times a day until they establish a regular feeding pattern. To stimulate urination and defecation, the anogenital area should be gently stroked with a warm, wet cotton-tipped applicator. HUSBANDRY

Rabbits can be housed indoors or outdoors. Wire cages are preferable to aquariums as they provide better ventilation and allow feces and urine to fall through the floor. Cages should be three times the length of the rabbit when fully stretched out (Bradley, 2001). A portion of the cage can be bedded with straw, shavings, or cardboard to provide a resting place off the wire. Aromatic wood shavings, such as pine and cedar, can cause respiratory and dermatological problems and have been associated with elevated liver enzymes (Bradley, 2001). Rabbits can be easily trained to use a litter box, as they commonly urinate and defecate in the same place repeatedly.

52

Outdoor housing should provide shade and shelter from wind and temperatures below 39.2 °F (4 °C). Rabbits are more tolerant of cold temperatures than heat and are generally intolerant of temperatures above 82.4 °F (28 °C) as they are unable to sweat and they pant ineffectively (Donnelly, 2004). NUTRITION

Rabbits are strict herbivores. The ideal diet for maintenance is comprised of a good quality pelleted feed with a protein content of 16% and a fiber content of 16% (Brooks, 2004). Unlimited amounts of grass hay should be offered daily. Timothy hay is preferred over legume hays such as alfalfa. A minimum of 1 cup of fresh leafy vegetables per each 4 lb of body weight should be offered daily. Vegetables high in oxalates, such as spinach, kale, and cabbage should be fed sparingly. Free-choice feeding of pelleted food alone can result in overeating, obesity, and diarrhea. ENRICHMENT

Toys and other distractions are beneficial to promote activity and prevent boredom in caged rabbits. Sturdy plastic, nontoxic toys are appropriate. A tunnel or hidebox can simulate a burrow in the wild. HANDLING AND RESTRAINT

As mentioned previously, proper restraint is imperative for rabbits to prevent skeletal injuries. One hand should lift and support the rear end, with the other grasping the forelegs. Rabbits should not be lifted by the ears or scruff. With proper restraint, rabbits can be safely carried and restrained for physical examinations. PHYSICAL EXAMINATION

The examination table should be covered with a towel to prevent slipping. To facilitate abdominal palpation, roll the rabbit on its back and cradle it against your abdomen. This posi-

Exotic Small Mammal Care and Husbandry

tion is also helpful for examining the perineal region and taking a rectal temperature. Oral examination is very challenging in rabbits due to the small size of their oral cavity. An otoscope cone with a light source can be used to visualize the caudal aspects of the oral cavity. Many specialized products are now available to assist in oral examination in rabbits. For more detailed oral examination, chemical restraint is often required.

CLINICAL TECHNIQUES

Blood samples can be obtained from multiple readily accessible sites in rabbits: the marginal ear vein, central ear artery, lateral saphenous vein, and the jugular vein (under anesthesia). For smaller rabbits, it is preferable to puncture the vein with a 25- or 27-gauge needle and allow blood to drip from the needle hub into a collection tube, as the use of a syringe generally causes collapse of small vessels. Annual blood work is recommended for rabbits older than 4 years to screen for common geriatric conditions. Reference ranges for hematological and biochemical values are presented in Table 4.2. Cystocentesis can be performed in rabbits by a technique similar to that used in cats. Rabbits should be scruffed with one hand, with feet restrained by the other, on their backs. Samples should be analyzed using standard methods. Interpretation of results should take into consideration that pigment and mineralization is normally found in rabbit urine. Normal urinalysis values in rabbits can be found in Table 4.3. Fecal examination should be performed in juvenile rabbits and in any rabbit presenting for diarrhea. A direct smear should be performed to evaluate for coccidea and to check for the presence of intestinal parasites. Rabbit feces normally contain a moderate amount of yeast organisms. Indwelling catheters are indicated in hospitalized rabbits that are critically ill, to deliver intravenous (IV) medications and fluid therapy. The preferred sites for intravenous catheter placement are the saphenous and cephalic veins. Complications associated with phlebitis have been reported with indwelling catheters in the ear veins (Mader, 2004).

Rabbits

53

Table 4.2 Reference ranges for hematology and serum biochemical values for rabbits.

Table 4.3 urinalysis.

Value

Specific gravity

1.003–1.036

pH

8.2

Crystals

Calcium carbonate monohydrate, anhydrous calcium carbonate, ammonium magnesium phosphate

Casts, cells, bacteria

Rare

Reference Interval

RBC (×10 cells/μL)

4.9–7.8

Hemoglobin (g/dL)

10.0–17.4

6

Hematocrit (%) WBC (×103 cells/μL)

31–50 5.2–12.5

Reference

Neutrohphils (%)

20–75

WBC

Occasional

Lymphocytes (%)

30–85

RBC

Occasional

ranges

Monocytes (%)

2–10

Albumin

Occasional in young

Eosinophils (%)

0–5

130 mL/kg/day

Basophils (%)

0–8

Average urine production

Platelets (×103 cells/μL) Total blood volume (mL/kg)

250–650 55–70

Total protein (g/dL)

5.4–8.3

Albumin (g/dL)

2.4–4.6

Globulin (g/dL)

1.5–2.8

Glucose (mg/dL)

75–155

Cholesterol (mg/dL)

10–80

Blood urea nitrogen (mg/dL) Creatinine (mg/dL)

13–30 0.5–2.5

Aspartate aminotransferase (U/L)

14–113

Alaline aminotransferase (U/L)

14–80

Alkaline phosphatase (U/L) Total bilirubin (mg/dL) Sodium (mmol/L) Potassium (mmol/L) Chloride (mmol/L)

4–16 0.0–0.75 131–155 3.6–6.9 92–112

Phosphorus (mg/dL)

2.3–6.9

Calcium (mg/dL)

5.6–14

From: Carpenter (2005); Mader (2004); Vennen and Mitchell (2008).

for

rabbit

From: Carpenter (2005); Mader (2004); Vennen and Mitchell (2009).

Oral medications are best delivered in a suspension form. Alternatively, tablets can be crushed and mixed with a palatable nutritional supplement and offered by mouth (PO). Nasogastric intubation can be performed in patients that require delivery of nutritional support [Critical Care for Herbivores, Oxbow pet products (www.oxbowanimalhealth.com), Murdock, NE]. PREVENTIVE HEALTH

There are no routine vaccinations recommended for pet rabbits. COMMON DISEASES

The rabbit formulary is presented in Table 4.4.

Gastrointestinal diseases Preferred sites for intramuscular (IM) injection are the large epaxial muscles on either side of the spine or the quadriceps. Volumes from 0.25 to 1.5 mL can be safely administered depending on the size of the rabbit. Subcutaneous (SC) injections and fluids can be delivered in the loose skin over the shoulders. Up to 100 mL volume of replacement fluids can be administered to mildly dehydrated rabbits. Intravenous injections can be administered in the lateral saphenous or cephalic veins.

Many gastrointestinal problems in rabbits are induced by feeding inappropriate diets that alter the intestinal microflora and affect pH and motility. Gastric stasis syndrome is common in rabbits and is associated with a low-fiber high-carbohydrate diet, stress, decreased exercise, and hair ingestion (Jenkins, 2004). Rabbits present with prolonged anorexia and decreased stool production. Radiographs may not be helpful in differentiating between this condition and gastric trichobezoar (hair

Table 4.4 Rabbit formulary. Agents

Dosage (mg/kg)

Route

SC, IM, IV

Antimicrobial Agents Amikacin

5–10 divided q8–24h

Amoxicillin

Do not use

Amoxicillin/clavulanic acid

Do not use

Ampicillin

Do not use

Cephalexin

11–22 q8h

PO

Ciprofloxacin

10–22 q12–24h

PO

Clindamycin

Do not use

Doxycycline

2.5 q12h

PO

Enrofloxacin

5–15 q12h

PO, SC, IM

Gentamicin

4 q24h

SC, IM

Metronidazole

20 q12h

PO

Penicillin G

40–60,000 IU/kg q48h

SC

Trimethoprim-sulfa

30 q12h

PO, SC

Griseofulvin

12.5 q12h

PO

Lime sulfur dip (2.5%)

Dip q7d for 4 treatments

Topical

Fenbendazole

10–20 repeat in 14 days

PO

Imidacloprid

1 cat dose q30d

Topical

Ivermectin

0.2–0.4 q10–14d

SC

Lufenuron

30 q30d

PO

Antifungal Agents

Antiparasitic Agents

Praziquantel

5–10 repeat in 10 days

PO, SC, IM

Pyrantel pamoate

5–10 repeat in 14 days

PO

Sulfadimethoxine

50 once, then 25 mg/kg q24h for 10–20 days

PO

Selamectin

6–10

Topical

Sulfmerazine

100

PO

Sulfaquinoxaline

1 mg/mL

Drinking water

Chemical Restraint, Anesthesia, Analgesia Acepromazine

0.25–1.0

IM

Atipamazole

0.001 for medetomidine reversal

SC

Atropine

0.1–0.5

IM, SC

Buprenorphine

0.01–0.05 q6–12h

SC, IM, IV

Butorphanol

0.1–0.5 q4–6h

SC, IM, IV

Carprofen

1–2.2 q12h

PO

Diazepam

1–3

IM, IV

Flunixin meglumine

0.3–2.0 q12–24h

SC, IM

Glycopyrrolate

0.01–0.02

SC

Isoflurane

3%–5% for induction, 2%–3% for maintenance

Inhalation

Ketamine

20–50

IM

Ketamine + acepromazine

25–40(K)/0.25–1.0 (A)

IM

54

Rabbits

55

Table 4.4 Continued Agents

Dosage (mg/kg)

Route

Ketamine + diazepam

10–15(K)/0.3–0.5 (D)

IM, IV

Ketamine + medetomidine

0.35 mg/kg(M) IM, 5–20 mg/kg(K) IV 15 minutes later

IM + IV

Ketamine + midazolam

25(K)/2–5(M)

IM

Ketoprofen

1 q 12–24h

SC, IM

Medetomidine

0.25

SC, IM

Meloxicam

0.1–0.2 q24h

PO

Midazolam

1–2

IM

Morphine

2–5 q4h

IM

Naloxone

0.01–0.1

SC, IP

Oxymorphone

0.05–0.20 q8–12h

SC, IM

Pentobarbital

20–45

IP

Propofol

2–3 mg/kg for induction, maintain with 1 mg/kg

IV

Yohimbine

0.5–1.0

IM, IV

Miscellaneous Agents Calcium gluconate

100

IM

Cimetadine

5–10 q8–12h

PO, SC, IM, IV

Cisipride

0.5 q8–12h

PO

Dexamethasone

0.5–2.0

IM, SC, IV

Diphenhydramine

2

SC

Epinephrine

0.2

IV

Furosemide

2–5 q12h

PO, SC

Metoclopramide

0.5 q8–24h

PO, SC, IM

Oxytocin

0.1–3.0 IU/kg

SC, IM, IV

Papain enzyme

1–2 tablets q24h for 3–5 days

PO

Pineapple juice

10 mL/animal q24h for 3–5 days

PO

Prednisone

0.5–2.0 q12h

PO

From: Carpenter (2005); Morrisey and Carpenter (2004).

ball), which will have a similar radiographic appearance and presentation. Rabbits are often treated symptomatically with oral lubricants, protein-digesting agents (e.g., papain, pineapple juice), rehydration, and force-feeding (fruit or vegetable baby food) to stimulate gastric motility. Antibiotics and motility-enhancing agents are sometimes indicated. Rabbits requiring surgical treatment for this condition have a poor prognosis. Enteritis caused by bacterial agents is a common clinical disease in pet rabbits. Symptoms range from mild diarrhea with soft or pasty stools to acute, severe enterotoxemia progressing to death. Clostridium spiroforme is the primary causative agent of enterotoxemia

in rabbits. Recently weaned animals are at risk because they have an undeveloped population of gut microflora, which allows the etiologic agent to proliferate. Affected animals exhibit clinical signs including watery brown diarrhea, anorexia, dehydration, polydipsia, pyrexia or hypothermia, bloat, and grinding of teeth (Suckow et al., 2002). Infection is generally fatal within 48 hours. Colibacillosis is caused by a pathogenic strain of Escherichia coli. This disease most commonly affects post-weaning rabbits. Morbidity and mortality rates vary depending on the serotype, but they can range from mild diarrhea to 50% mortality. Affected rabbits should be treated with supportive care and

56

appropriate antibiotics based on culture results. Tyzzer’s disease, caused by Clostridium piliforme, occurs in many species, including rabbits. Affected rabbits develop profuse, watery diarrhea, anorexia, and dehydration and typically die within 1–2 days. Treatment is often unsuccessful, but proper sanitation can prevent the disease. Proliferative enteropathy, caused by Lawsonia intracellularis, has been reported in rabbits. Weanlings are most commonly affected. They develop diarrhea, depression, and dehydration. The disease is rarely fatal and runs its course in 1–2 weeks. Dysbiosis is a common cause of enteritis in rabbits and is caused by the administration of antibiotics that disrupt the normal bacterial flora of the gastrointestinal tract resulting in proliferation of pathogenic bacteria. Clindamycin, lincomycin, ampicillin, amoxicillin, amoxicillin–clavulanic acid, cephalosporins, many penicillins, and erythromycin can induce this condition in rabbits (Jenkins, 2004). Several enteric viruses can affect rabbits and cause gastrointestinal disease. Rotavirus is mildly pathogenic, but can result in serious clinical disease when rabbits are co-infected with E. coli. Coronavirus outbreaks have been reported. Clinical signs include diarrhea, abdominal swelling, and death. Rabbit caliciviral disease (RCD), formerly rabbit hemorrhagic disease, was first reported in the United States in 2000. Rabbits older than 2 months are typically affected. Clinical signs include abdominal distension, constipation, diarrhea, tachypnea, and cyanosis. Morbidity is high with mortality approaching 100%. Coccideosis is a common cause of enteric disease in rabbits. At least 12 species of Eimeria spp. are reported to infect rabbits, with varying pathogenicity. Symptoms range from mild to severe, generally depending on the parasite burden and immune status of the rabbit. Diagnosis is made by identification of the oocysts in feces. Prevention of the disease can be accomplished by strict sanitation and avoiding infected feces and contaminated drinking water. Sulfa drugs have been found to be safe and effective as treatments in rabbits. Pinworm infections are common in rabbits. Two species are commonly reported, Passal-

Exotic Small Mammal Care and Husbandry

urus ambiguus and P. nonanulatus. Treatment with fenbendazole 10–20 mg/kg PO repeated in 10–14 days has been successful at eliminating the infection. Piperazine added to drinking water at a dose of 200 mg/kg PO repeated in 10 days has also been effective (Jenkins, 2004).

Respiratory disease Respiratory disease in rabbits is caused primarily by bacterial agents. Pasturellosis is a common disease in pet rabbits and is caused by the gram-negative coccobacillus Pasturella multocida. Upper respiratory signs (rhinitis, sinusitis, conjunctivitis), are commonly referred to as “snuffles.” The infection can extend to the middle ear canal and result in otitis. Signs of inner ear involvement include torticollis, nystagmus, and ataxia. Radiographs can assist in a diagnosis of otitis media by illustrating soft tissue opacity within the bulla and thickening of the normally thin-walled bullae. Hematogenous spread of the disease can result in septicemia, pneumonia, pleuritis, pericarditis, and generalized abscessation. Pasturellosis is less common in pet rabbits than in past years with the establishment of Pasturella-free rabbitries. Treatment should include supportive care and antibiotic therapy based on culture and sensitivity. No vaccine is currently available for prevention. Bordatella bronchiseptica is a respiratory pathogen in rabbits, guinea pigs, dogs, cats, and pigs. Clinical signs include serous nasal discharge, bronchopneumonia, and pleuritis in weanling rabbits. It is suspected as a co-pathogen and predisposing factor for P. multocida infections (Deeb, 2004).

Reproductive and urogenital disease Uterine adenocarcinoma is the most common neoplasia in rabbits. Certain breeds report an incidence of 50%–80% in rabbits older than 4 years (Pare and Paul-Murphy, 2004). Early clinical signs may be hematuria or serosanguinous vaginal discharge. Tumors typically metastasize to lung, liver, and other organs. Radiography and ultrasound can assist in establishing a diagnosis. Pulmonary metastasis carries a grave prognosis. Ovariohysterectomy

Rabbits

should be recommended for pet rabbits prior to 2 years of age to prevent this disease. Pyometra and endometritis can occur in breeding rabbits. Clinical signs include abdominal enlargement, vaginal discharge, anorexia, and lethargy. Abdominal ultrasound and cytological assessment of vaginal discharge can be performed to support the diagnosis. Pregnancy toxemia is a metabolic disease that occurs in the last week of gestation. Predisposing factors include obesity, stress, and anorexia. Anorexia, weakness, ataxia, dyspnea, and coma progressing to death are common clinical presentations. Treatment is usually unrewarding. Prevention hinges on providing adequate nutrition and husbandry in late gestation. Treponematosis, commonly known as rabbit syphilis or vent disease, is caused by the spirochete Treponema paraluiscuniculi. Typical lesions occur on the vulvar or preputial region, though autoinfection can lead to facial lesions. Lesions begin as vesicles and papules and progress to crusts and scales. Diagnosis is based on serological testing or skin biopsy. Rabbits can be successfully treated with parenteral penicillin (Penicillin G benzathine–penicillin G procaine at 42,000 to 84,000 IU/kg SC at 7-day intervals for three injections) (Pare and PaulMurphy, 2004). Rabbits with hypercalcuria are predisposed to the formation of uroliths. This condition is more common in obese rabbits that are fed a free-choice pelleted diet and/or alfalfa hay. Clinical signs include anorexia, lethargy, hematuria, stranguria, grinding of teeth, and urine scald of the perineum. Treatment depends on the location of the lesion and ranges from urohydropropulsion to cystotomy. Dietary modification is critical for prevention and treatment.

Neurological and musculoskeletal disease Encephalitozoonosis is caused by infection with the protozoan parasite Encephalitozoon cuniculi. Clinical signs include head tilt, behavioral changes, ataxia, nystagmus, or seizures. Diagnosis is based on serology in rabbits exhibiting clinical signs. Elimination of the parasites is accomplished by treatment with anthelmintics (albendazole, oxibendazole, fendabazole).

57

Pasturellosis should be considered as a differential diagnosis for head tilt. Splay leg is a common musculoskeletal condition that occurs in young rabbits, several days to months old. Affected animals cannot adduct their limbs and have difficulty ambulating to food and water. Euthanasia is usually indicated. This condition is an inherited disease and, as such, breeding of affected individuals and parents should be discouraged (Suckow et al., 2002). Traumatic vertebral fracture is the most common cause of posterior paresis and paralysis in rabbits, with lumbar vertebra 7 (L7) most often affected. The history typically includes a traumatic incident involving struggling or restraint. Clinical signs include paresis and urinary or fecal incontinence. Radiographs are diagnostic. In most cases, euthanasia is indicated. In less severe cases, conservative medical management includes administration of nonsteroidal anti-inflammatory drugs, manual bladder expression, and, in some cases, use of a wheelchair (Deeb and Carpenter, 2004).

Dermatological diseases Ulcerative pododermatitis, commonly called sore hocks, is a chronic ulcerative dermatitis of the plantar metatarsal and metacarpal regions of the feet. Animals confined in small cages with wire floors are predisposed to this condition. Obesity, stress, and poor sanitation are also contributing factors. Treatment involves cleaning and debriding necrotic tissue, bandaging, and using topical and systemic antibiotics. Dermatophytosis, commonly called ringworm, is a zoonotic disease that is usually selflimiting and often asymptomatic in rabbits (Hess, 2004). Trichophyton mentagrophytes is most commonly isolated. Diagnosis is based on fungal culture or on identification of fungal forms on KOH prep. Treatment consists of the application of topical and administration of systemic antifungal agents for 3–4 months. Disinfection of the environment is essential to prevent reinfection. Rabbits are susceptible to mite infestation with the ear mite, Psoroptes cuniculi (Fig. 4.4). Clinical signs of mite infestation include crusting of the external ear canal, pruritis, and head shaking. Recommended treatment is with iver-

58

Fig. 4.4 Mite infestation with Psoroptes cuniculi. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

mectin (Ivomec, Merck, AgVet Division, Rahway, NJ) 0.4 mg/kg SC q12–14 days for three treatments. Cheyletiella spp. are nonpruritic mites that infest the area over the scapulae. Lesions are typically mild and nonpruritic. Diagnosis is based on skin scraping. Sarcoptes scabiei and Notoedres cati are burrowing mites that cause intense pruritis, alopecia, and abrasions. Skin scrapings are diagnostic and treatment with ivermectin is recommended. Myiasis is a condition encountered by rabbits housed outdoors in warm environments. The larvae of Cuterebra species, or bot flies, infest the subcutaneous tissue, especially the dorsum, inguinal, and ventral cervical regions. A breathing hole on the surface is usually visible. Surgical excision of the larvae and debridement of necrotic tissue is indicated. REFERENCES American Rabbit Breeders Association. www. arba.net/Breeds.htm (accessed November 4, 2009). Antinoff, N. 1999. Physical Examination and Preventive Care of Rabbits. Veterinary Clinics of North America: Exotic Animal Practice 2(2):405–427. Bradley, T.A. 2001. What Every Veterinarian Needs to Know About Rabbits. Exotic DVM 3(1):42–46.

Exotic Small Mammal Care and Husbandry

Brooks, D.L. 2004. Nutrition and Gastrointestinal Physiology. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 155–160. Carpenter, J.W. 2005. Exotic Animal Formulary. Third edition. Elsevier Saunders, St. Louis, MO, 440–441. Deeb, B.J. 2004. Respiratory Disease and Pasturellosis. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 172–182. Deeb, B.J., and Carpenter, J.W. 2004. Neurologic and Musculoskeletal Diseases. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 203–210. Donnelly, T.M. 2004. Basic Anatomy, Physiology, and Husbandry. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 136–146. Hess, L. 2004. Dermatologic Diseases. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 194–202. Jenkins, J.R. 2004. Gastrointestinal Diseases. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 161–171. Mader, D.R. 2004. Basic Approach to Veterinary Care. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 147–154. Morrisey, J. K., and Carpenter, J.W. 2004. Formulary. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 436–444. Pare, J.A., and Paul-Murphy, J. 2004. Disorders of the Reproductive and Urinary Systems. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 183–193. Suckow, M.A., Brammer, D.W., Rush, H.G., and Chrisp, C.E. 2002. Biology and Diseases of

Rabbits

Rabbits. In Fox, J.G., Anderson, L.C., Loew, F.M., and Quimby, F.W. (eds.). Laboratory Animal Medicine. Second edition. Academic Press, San Francisco, CA, pp. 329–364. Suckow, M.A., and Douglas, F.A. 1997. The Laboratory Rabbit. CRC Press, Boca Raton, FL.

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Vennen, K.M., and Mitchell, M.A. 2009. Rabbits. In Mitchell, M.A., and Tully, T.N., Jr. (eds.). Manual of Exotic Pet Practice. Saunders, St. Louis, MO, pp. 375–405.

Ferrets

COMMON BREEDS

The domestic ferret—Mustela putorius furo, which loosely translates as “mouse-eating smelly thief”—is a descendent of the European polecat (Fig. 5.1). The North American blackfooted ferret, Mustela putorius nigripes, is another popular breed acquired as a pet. In general, ferrets make good pets because they are playful and friendly. They can be trained to use a litter box and to come when called, and they are most active during the early morning and evening hours. Ferrets were initially maintained for vermin control because they are small and can fit into tight spaces. They are expert predators and are naturally curious of their surroundings, making them suitable for rabbit hunting as well. Ferrets

5 are used in biomedical research to investigate areas of virology, toxicology, endocrinology, and reproductive physiology (Marini et al., 2002). BASIC ANATOMY AND PHYSIOLOGY

The long tubular body of the ferret allows them to get into small spaces, such as holes in the ground, during hunting. Their coat color can be categorized as sable/wild, albino, cinnamon/ sandy, silver, black-eyed white, chocolate, Siamese, panda, or shetland sable. They molt in the spring and fall routinely accompanied by some color changes in the coat. Females will lose their hair after ovulation, with regrowth after each successful mating. Neutered ferrets do not have as dramatic changes in molting or color changing as intact ferrets. A ferret’s coat color may change considerably over time, making it not as useful a form of identification as microchips or tattoos. REPRODUCTION AND SEXING

Fig. 5.1 Normal ferret (copyright Eric Isselée, Dreamstime.com). For color detail, please see color plate section.

Male ferrets are referred to as hobs, females are jills, and they are easy to differentiate. Hobs have a preputial opening midabdomen, the os penis can be easily palpated under the skin, and testicles are located cranioventral to the anus if neutering has not yet been performed. Jills have a small, distinct vulva and a shorter anogenital distance. Males are usually larger in size than females, particularly if they have not been castrated (Fig. 5.2). 61

62

Exotic Small Mammal Care and Husbandry

Table 5.1 Biological profile and normal physiologic values.

Fig. 5.2 Male ferret (left) and female ferret (right) size differentiation. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Most ferrets sold as pets in the United States are neutered and de-scented by 5–6 weeks in an effort to reduce aggression and minimize their odor. Breeders will usually delay neutering until puberty. Some elect delayed neutering in an attempt to minimize the development of adrenal disease later in life. It is thought the neutering removes the natural hormonal negative feedback, resulting in adrenal hyperplasia or neoplasia from persistently elevated levels of gonadotropic luteinizing hormone (LH) (Kiefer and Johnson, 2006). Jills are induced ovulators and experience a prolonged estrus. Aplastic anemia develops if they do not ovulate; therefore they should be spayed if they are not going to be bred. Jills reach sexual maturity by 9–12 months of age and are sexually active from March to August unless the photoperiod is adjusted, which can change the onset of estrus and prolong the breeding period. During this time both jills and hobs have an increased odor from their scent glands, oil secretion in the coat, and urine. White fur will become yellow as a result of the increased oil production (Brown, 2004). The onset of estrus is noted by vulvar swelling and changes in vaginal cytology. Mating can appear quite violent, but if the female is receptive she will become limp when the male grasps her by the neck. If mating is not successful, the jill may experience pseudopregnancy. (The biological profile of ferrets is presented in Table 5.1.)

Body weight

Adult male: 800–3,000 g Adult female: 700–1,200 g

Rectal temperature

100 °F–104 °F (37.7 °C–40 °C)

Reproductive data

Gestation length: 42 days Weaning age: 6–8 weeks Seasonally polyestrous Induced ovulators Litter size: 1–18 (average 8) Birth weight: 6–12 g Sexual maturity: 6–12 months

Life span

5–8 years

Heart rate

200–255 beats per minute

Respiratory rate

33–36 breaths per minute

Food consumption

43 g/kg/day

Water consumption

75–100 mL/day

Dental formula

2(I 3/3, C 1/1, P 4/3, M 1/2)

Urine volume

26–28 mL/day

From: Brown (2004); Kiefer and Johnson (2006).

Jills can have 1–2 litters per year under natural lighting, but 3–4 litters may be possible with manipulation of the photoperiod. An average litter size is 8 kits, but can range from 1 to 18 kits. Gestation normally lasts 42 days, and it is best to single-house pregnant jills for the last 2–3 weeks of gestation. A nesting box or similar materials should be available, and there should be minimal stress to prevent cannibalization of the newborn kits. Kits are born with a thin white hair coat and are blind and deaf. Their eyes and ears open at 32–34 days of age after they have become active and are eating soft food, which can occur as early as 21 days of age. Kits are usually weaned by 6–8 weeks of age or 300–450 g body weight (Brown, 2004). UNIQUE FEATURES OF IMPORTANCE

There are many characteristics unique to ferrets that owners should be aware of. For instance, male ferrets will typically become twice the size of female ferrets if allowed to become sexually mature prior to being neutered. Also, ferrets do

Ferrets

not have sweat glands and therefore are prone to overheating. They also have very good night vision and sense of smell, which aid them in hunting. Ferrets have a pair of anal glands or “scent glands” that contribute to their musky odor and are routinely removed or “de-scented” by 5–6 weeks of age when they are neutered. Sebaceous secretions of the skin also contribute to their musky odor, and they can be bathed frequently as well as have their cages cleaned routinely to manage the odor. There are some unique features of the ferret that should be taken into account both before and after surgery. Because the gastrointestinal transit time is 3–3.5 hours, ferrets should not be fasted more than 3–6 hours or their blood glucose levels will be significantly affected. Ferrets are also very susceptible to acetaminophen toxicity like cats. Caution should be taken when using any nonsteroidal anti-inflammatory drug (NSAID), and the cyclooxygenase 2 (COX-2) drugs may be better choices for pain management (Quesenberry and Orcutt, 2004).

HOUSING

Ferrets can be housed both indoors and outdoors, depending upon the climate. Open wire cages with solid or wire floors are designed for ferrets in many sizes and designs with multiple levels. These are ideal for adequate ventilation and ease of sanitation. If wooden cages are handmade, care should be taken to eliminate sharp edges and corners as well as to make them easy to sanitize. Outdoor enclosures need to have a shaded area for protection from the sun and heat. Nest boxes should also be provided to allow for a safe, dark area for sleeping. They often prefer to sleep in a hammock, towel, or t-shirt, although rips, holes, or unraveled edges should be avoided to prevent strangulation (Fig. 5.3). These items can also be washed frequently to minimize their musky odor. Enrichment is essential for ferrets, in addition to roaming time outside the cage. Ferrets are escape artists, so all cages should be secure and checked frequently for possible escape routes. If a ferret can fit its head through an opening, its body will likely follow.

63

Fig. 5.3 Ferret in loose towel used for burrowing and sleeping in cage.

HUSBANDRY

Ferrets are very social and should be pair- or group-housed, as long as they have been neutered or are all females to prevent aggression or unintended breeding. Ferrets are very playful, which can sometimes be confused with aggression because they will often bite each other on the nape of the neck. Ferrets should be monitored as play can sometimes lead to aggressive actions. Hissing, screaming, and jaw snapping are defensive behaviors to watch for. They will elicit a loud high-pitched scream when they are afraid, which is not a sign of pain. One way to prevent play biting at the nape of the neck or nipping at people’s ankles, hands, and feet is to put a bitter-tasting substance on the area. There are many commercially available products for this purpose (Brown, 2004). Cages should be cleaned as needed based upon the number of ferrets kept together and the mess that they create, but weekly cleaning is typically sufficient. They can be litter box trained, making cage cleaning and changing much easier. Ferrets tend to back up in the corner of the box to urinate and defecate, so the sides of the litter box should be tall enough to contain the waste. Aspen shavings, recycled paper products, or commercial pelleted litter should be used for bedding and litter instead of cedar or pine shavings or clay/clumping cat litter. Ferrets should have access to a litter box in play areas as well because they are not

64

Exotic Small Mammal Care and Husbandry

always able to reach the cage in time to use the box due to their short gastrointestinal tract. Food can be provided in dishes while water bottles are typically placed on the sides of the cage. Galvanized materials should be avoided to prevent zinc toxicity, which can occur if they chew on the devices. Ferrets will usually eat about 43 grams of food per kilogram of body weight per day (g/kg/day) and drink 75–100 mL of water each day. Food and water should be provided ad libitum as long as they do not become obese, in which case slight food restriction becomes necessary.

colic valve such as other animals have (Willard, 2002). Because of this, they need to eat frequently and be provided a highly digestible formulation. Ferrets can usually be given free access to food, as they rarely overeat and become obese. Nutrition is critical to the reproductive success of jills as well. Inadequate diet can cause decreased conception rates and small litter sizes, and it may contribute to the development of pregnancy toxemia. They should be fed a high-calorie diet with meat products between litters if they are bred routinely (Bell, 2004b).

NUTRITION

Ferrets are obligate carnivores that require diets high in fat (15%–20%) and protein (30%–35%) and very low in fiber because it is not digestible (Kiefer and Johnson, 2006). Commercial diets are now available that are specially formulated for ferrets to be nutritionally complete and balanced. Historically, owners would provide a mixture of ferret chow, cat or kitten foods, and supplements that now are not necessary. Dairy products, sugary treats such as fruits, and high-fiber foods such as vegetables should be avoided. The transit time of the digestive tract of ferrets is about 3 hours. Ferrets have limited absorptive capacity because of their short gastrointestinal tract, minimal epithelial folding of the colon, low concentrations of some brush boarder enzymes, and lack of a cecum or ileo-

a Fig. 5.4

ENRICHMENT

Ferrets should have a few hours of play outside the cage each day. Also, the more time a ferret spends inside a cage, the more enrichment it needs (Fig. 5.4a,b). Because of their curious nature and ability to fit into small spaces, the outdoor play area should be “ferret-proofed” to block off any holes or openings to other areas from which it would be difficult to retrieve the ferret. The area should be checked each time to be sure new defects have not formed that would allow the ferrets to escape and investigate new territory. When left out of their cages to roam and play, ferrets should be carefully supervised to prevent ingestion of harmful substances or objects. Furniture should be covered on the bottom with wood or some sort of material to prevent chewing and burrowing into foam

b (a and b) Enrichment devices within cage or play area.

Ferrets

rubber or furniture and mattresses. Any items in the area such as shoes, rubber bands, electric cords, and dog or cat toys should be removed as well. These items can pose significant health risks if ingested and could cause an obstruction of the intestines. Toys that are provided both

65

inside and outside the cage should not be made of rubber or latex, but instead should be items such as paper bags, hard plastic toys, and tunnels of dryer exhaust tubing to allow for safe burrowing activity and entertainment (Kiefer and Johnson, 2006). HANDLING, RESTRAINT, AND PHYSICAL EXAM

Fig. 5.5 Manual restraint of a ferret while distracting with Nutri-Cal. For color detail, please see color plate section.

a

Most ferrets are docile and can easily be handled, but they will bite without warning so it is best to ask the owner if the ferret has a history of biting. Younger ferrets will have more a tendency to nip, as well as nursing females or ferrets that have not been handled much. It is important to know the laws in your area for unvaccinated and vaccinated ferrets in case someone is bitten during the course of the exam. Animals that are well socialized can typically be handled on the table with light restraint

b

Fig. 5.6 (a and b) Manual restraint options for physical exam or manipulations. Note the “yawn” reaction in Fig. 5.6b. (Photos courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

66

Exotic Small Mammal Care and Husbandry

for most of the exam. Ferrets can also be distracted with Nutri-Cal or canned food while a simple examination is performed or in conjunction with restraint during a procedure (Fig. 5.5). The ferret can picked up and supported while the abdomen is palpated and the thorax auscultated. They should be scruffed at the base of the neck for vaccinations or any procedure that may cause the animal to attempt to escape or bite. For animals that have a history of biting or are stressed, they can be scruffed at the nape of the neck and suspended above the table. This method will usually calm the ferret to the point of yawning (Fig. 5.6a,b).

CLINICAL TECHNIQUES

Sample collection—venipuncture Blood can be collected from a variety of locations, depending on the amount of blood that is needed. Ferrets can usually be manually restrained and distracted with food while obtaining a sample, minimizing the need for anesthesia or sedation. If blood is being collected for blood glucose measurement, food should not be used as a distraction. Most laboratories can perform routine complete blood cell counts (CBC) and serum chemistries with about 1.5 mL of blood. Larger volumes of

blood can be collected from either the jugular vein or the cranial vena cava, but the lateral saphenous vein or cephalic vein can be used to collect smaller amounts of blood for tests such as packed cell volume (PCV) or a blood glucose reading. A 27- or 28-gauge needle or tuberculin syringe can be used in these locations. (Reference ranges for hematological and biochemical values are presented in Tables 5.2 and 5.3.) For jugular vein collection, the ferret can be restrained in a similar manner as the cat, with the head extended and the forelegs pulled toward the chest. The vein is held off by applying pressure in the sternal area with the thumb of the person collecting the sample. Visibility can be improved by shaving the neck and swabbing the site with alcohol. Depending on the size of the ferret, a 25- or 22-gauge needle and a 3 mL syringe can be used to collect between 1 and 3 mL to be placed in heparinized microtubules for the best blood-to-plasma ratio (Taylor, 2001). Once the jugular is accessed, the head can be manipulated up and down to aid in pumping blood into the syringe more quickly.

Table 5.3 Laboratory normal values—complete serum biochemical values. Biochemical Parameter

Reference Interval

Total protein (g/dL)

5.9–6.0

Table 5.2 Laboratory normal values—complete blood cell count.

Albumin (g/dL)

3.4–3.5

Globulin (g/dL)

2.4–2.6

Hematologic Parameter

Glucose (mg/dL)

Reference Interval

RBC (×106 cells/μL)

9.3–9.69

Hemoglobin (g/dL)

16.2–16.8

Hematocrit (%)

48.4–49.8

WBC (×10 cells/μL) 3

7.0–9.2

Neutrohphils (%)

47–50

Lymphocytes (%)

45–48

Cholesterol (mg/dL)

93–134 158–183

Blood urea nitrogen (mg/dL)

10–45

Creatinine (mg/dL)

0.4–0.9

Total Bilirubin (mg/dL)

0.2

Aspartate aminotransferase (IU/L)

76–97

Alaline aminotransferase (IU/L) 138–210 Alkaline phosphatase (IU/L)

31–84

Monocytes (%)

1.0–1.19

Eosinophils (%)

3–3.5

Potassium (mEq/L)

4.2–7.7

Basophils (%)

0–0.49

Chloride (mEq/L)

102–125

Sodium (mEq/L)

137–162

Platelets (×103 cells/μL)

730–766

Phosphorus (mg/dL)

8.0–11.8

Total blood volume (mL)

50–60 mL/kg

Calcium (mg/dL)

4.0–9.1

From: Kiefer and Johnson (2006); Lichtenberger (2005).

From: Kiefer and Johnson (2006).

Ferrets

Restraint for collection from the cranial vena cava is similar except that the ferret is in dorsal recumbency with the head, neck, and front legs positioned as described for jugular vein access. Anesthesia is recommended for fractious ferrets, but if the ferret is not anesthetized a second assistant should restrain the pelvis and rear legs. The notch between the manubrium and the first rib is located, and a 25-gauge needle is inserted at a 25- to 45-degree angle to the body directed toward the opposite rear leg (Quesenberry and Orcutt, 2004). The vein is very superficial and the heart is not threatened by this technique because it is located more caudally in the chest when compared with other animals (Taylor, 2001).

Drug administration Medications can be administered subcutaneously (SC), intravenously (IV), and intramuscularly (IM) as with most other species. Subcutaneous injections should be administered over the shoulders or in the flank regions where there is the most loose skin. This is a preferred route of administration over intramuscular injections due to the limited muscle mass of the ferret. The quadriceps and biceps femoris muscle groups are the most common sites for intramuscular injections. Both the cephalic and saphenous veins can be used for intravenous administration of drugs as well. Medications can also be administered orally (PO) in a liquid form and by oral gavage if necessary.

Sample collection—cystocentesis The techniques for collecting urine in ferrets are similar to those used for dogs and cats. A voided sample can be collected during natural micturition or as a result of manual expression of the bladder. A cystocentesis can be performed as well using a 25-gauge needle, though the ferret may need to be briefly anesthetized to prevent trauma to the thin bladder wall if the animal struggles. Ferrets can also be catheterized if necessary, though it can be difficult depending on the clinical presentation of the ferret. Male ferrets with adrenal disease can become “blocked” because the prostate gland enlarges such that it constricts the urethra,

67

making catheterization difficult (Quesenberry and Orcutt, 2004).

Sample collection—fecal samples Fecal samples can be collected for analysis or culture if necessary. A fresh sample can be taken from the cage for most routine screenings. Sometimes a fecal swab is needed and can be collected from the rectum after being moistened with sterile saline.

PREVENTIVE HEALTH

Vaccinations New ferrets should be quarantined for a minimum of 2 weeks before being introduced to other ferrets, followed by a physical examination, fecal examination, and administration of any vaccinations that are due. Ferrets should have a routine physical exam every 6–12 months and be vaccinated annually for rabies and canine distemper viruses. Care should be taken when vaccinating ferrets because they are prone to experience anaphylactic reactions to vaccinations, requiring veterinary treatment. Typically only a single vaccine will be given on a visit, with a 2- to 4-week interval between vaccinations. Animals should be closely monitored for a few hours following administration of a vaccine, and a premedication of antihistamine should be given to any ferret with a history of vaccine reactions. A ferret-approved rabies virus vaccine should be administered at 3 months of age and then annually. Due to the variation in state and local government requirements, veterinarians should contact the local governmental agencies to determine the requirements for their city and state. There are two canine distemper killed virus vaccines that are commercially available, Fervac-D and PureVax. Vaccination for canine distemper should follow a series of boosters in young ferrets at 6, 10, and 14 weeks of age followed by annual boosters (Kiefer and Johnson, 2006).

Endoparasites and ectoparasites Even though it is uncommon for ferrets to have endoparasites, they should be routinely evaluated for both ecto- and endoparasites during the physical exam. Endoparasites that may be

68

Exotic Small Mammal Care and Husbandry

detected during a fecal examination include coccidia (Isospora species), Giardia, and Cryptosporidium. Otodectes cynotis is the species of ear mites that is common to the ferret. An external exam of the ear can determine if an ear swab to check for ear mites is needed. Ferrets should also receive heartworm and flea and tick preventive year round. A dental prophylaxis may be needed annually as well, and routine blood work should be performed when ferrets are over 2–3 years of age. A fasting glucose level should be taken as part of the screening as well.

Neutering Ferrets are routinely spayed or castrated. The surgery can be performed as early as 4–6 weeks of age and should be done before 6 months of age in an effort to minimize odor. Their anal glands can be removed at the time of neutering; removal is recommended to minimize their musky odor. Owners should be warned that despite these procedures ferrets will still have a musky odor, though it will be less than that of an intact animal with intact anal glands.

COMMON DISEASES

Pancreatic tumors Ferrets between 3 and 8 years of age can develop a tumor of the pancreatic beta cells that will cause an overproduction of insulin. Both male and female ferrets are affected equally. This overproduction of insulin creates a state of hypoglycemia that can affect both the neurologic and adrenergic systems. Neurologic signs of hypoglycemia include mental dullness, lack of coordination, seizures, and coma. The adrenergic symptoms include increased heart rate, hypothermia, tremors, and irritability (Marini et al., 2002). Once diagnosed, the disease can be managed either medically or surgically depending on the severity of the disease and the health of the ferret. Medical management includes drug therapy with prednisone and diazoxide with dietary changes. Surgical excision of the affected portion of the pancreas is the treatment of choice in ferrets under 6 years of age or those that also have adrenal disease. Surgical

Fig. 5.7 Typical alopecia pattern associated with adrenal disease in ferrets. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.) For color detail, please see color plate section.

therapy will not necessarily cure the disease but will slow its progression considerably (Quesenberry and Rosenthal, 2004).

Adrenal disease Adrenal disease can occur when one or both of the adrenal glands becomes enlarged and overproduces steroid hormones. The adrenal enlargement is often due to the presence of adrenocortical tumors in ferrets between 3 and 6 years of age and may be closely linked to early spay and castration procedures (JohnsonDelaney, 2006). Bilaterally symmetrical hair loss in a very distinct pattern over the tail head, sacrum, flank, and lateral trunk is the most common clinical sign of the disease (Fig. 5.7). They may also be itchy or have a “pear-shaped” abdomen. Females will have an enlarged vulva and males may have difficulty urinating due to an enlarged prostate, both as a result of elevated hormone levels secreted by the overactive adrenal gland(s) (Fig. 5.8). Adrenal disease can be treated surgically or medically. Surgical excision of the affected gland is performed. It is not uncommon to have bilateral involvement, in which case one adrenal is completely removed and a partial adrenalectomy is performed on the contralateral gland (Antinoff et al., 2000). Medical management with drugs, such as leuprolide acetate or melatonin, will work to decrease sex steroid production from the overactive adrenal gland.

Ferrets

69

Therapy may consist of any combination of surgery, radiation, or chemotherapy. Animals may go into remission for 3 months to 5 years (Marini et al., 2002).

Skin tumors The most common epithelial tumors are basal cell tumors and mast cell tumors. They can occur anywhere on the body and are benign. Once they are surgically removed, they generally will not recur if all of the tissue was removed. Histological evaluation is necessary to distinguish these tumors from the malignant and metastatic squamous cell carcinomas and apocrine gland adenocarcinomas that have a guarded prognosis (Marini et al., 2002).

Gastrointestinal disease

Fig. 5.8 Typical vulvar swelling associated with adrenal disease in ferrets. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Medical management alone is an option if the owners are not able to afford surgery or the animal is not a good candidate for surgery. Ferrets that undergo surgical therapy alone do not appear to live as long as ferrets treated medically, and there appears to be a slight advantage to performing surgical debulking in conjunction with leuprolide acetate therapy (Johnson-Delany, 2006).

Lymphosarcoma Lymphosarcoma can affect ferrets of any age, but young ferrets less than 2 years of age most often develop leukemia and/or mediastinal lymphoma, and ferrets over 3 years of age will present with multicentric solid tumors. Clinically ferrets may have difficulty breathing, have enlarged peripheral lymph nodes on palpation, or have vague signs of lethargy, inappetence, and weight loss. A diagnosis may be made from a CBC or fine needle aspirates of affected lymph nodes or other organs involved such as the liver, spleen, or gastrointestinal tract.

Ferrets with gastrointestinal disease may have a range of clinical symptoms from vomiting, diarrhea, weight loss, inappetence, and lethargy to various degrees. There are several diseases that should be considered when evaluating a ferret for gastrointestinal problems. These include Helicobacter mustalae infection, proliferative bowel disease (PBD), epizootic catarrhal enteritis (ECE), inflammatory bowel disease (IBD), eosinophilic gastroenteritis, and foreign bodies. Helicobacter infection is common across many species and can cause severe ulceration of the stomach in ferrets. It can be diagnosed by culture of gastric biopsy samples. The disease can become apparent when animals are under stress from surgery, unrelated illness, changes in diet, and rapid growth. Ferrets may also have black, tarry stools or staining of the perianal region as a result of a bleeding gastric ulcer. Treatment for H. mustalae requires multidrug therapy and may be lifelong (Bell, 2004a). Lawsonia intracellularis is the causative organism of PBD. Proliferative bowel disease usually affects juvenile ferrets from 10 to 16 weeks of age that are rapidly growing and may be under environmental or nutritional stress. Transmission is likely fecal–oral but is on the decline, probably as a result of improved quality of care and nutrition. Ferrets with PBD may be more susceptible to other diseases because they are significantly debilitated by the disease.

70

Adult ferrets are most susceptible to ECE because it is highly transmissible and usually is associated with a recent exposure to a new, younger ferret that is an asymptomatic carrier of the disease. It is thought that a coronavirus is responsible for the disease. Though many ferrets can be affected, ECE has a low mortality rate when appropriate therapy is provided. Treatment involves supportive therapy with fluids, antibiotics, and isolation from other ferrets. Therapy may be long term and include steroids and diet change. The causative agent of IBD has not been identified but may be associated with a food allergy or any type of inflammatory process. Elevated serum chemistry values such as lipase and globulin levels help in predicting IBD. Inflammatory bowel disease usually has a gradual onset; it can be confirmed with surgical biopsies of various segments of the intestine as well as any enlarged lymph nodes, which may be an indication of progression to lymphoma when IBD is left untreated. Treatment is usually lifelong and aimed at dietary changes to novel proteins or to specially formulated diets for hypersensitivity in conjunction with immunosuppressive therapy with various immune modulator medications (Burgess and Garner, 2002). Eosinophilic gastroenteritis is a generalized inflammatory process similar to IBD but with the presence of elevated numbers of eosinophils. There is no specific agent identified as the cause of this disease, but a dietary allergy component and parasitism are suspected. Granuloma formation within the intestinal tract can be identified during surgery while obtaining biopsies. Therapy with parasite elimination, diet changes, and immunosuppression can be long term (Bell, 2004a). A foreign body should be considered when a ferret is having gastrointestinal signs. Due to their curious nature and habit of chewing on items in their environment, it is not uncommon for ferrets to ingest foreign objects that can cause a blockage or obstruction of the gastrointestinal tract. Surgical therapy to remove the object is needed and careful supervision of items available in their environment will be essential to prevent a recurrence.

Exotic Small Mammal Care and Husbandry

Canine distemper Canine distemper virus (CDV) is one of the most common respiratory diseases of ferrets. It is spread by aerosol exposure as well as direct contact with infected feces, urine, and skin. Once an unvaccinated ferret is exposed it will start to exhibit signs in 7–10 days. Ferrets will develop pneumonia resulting in trouble breathing, nasal discharge, fever, lethargy, inappetence, cyanotic mucus membranes, and abnormal lung sounds. Mortality rates associated with CDV infection in ferrets is near 100% because there is no specific treatment for the disease. However, CDV can be prevented with vaccination.

Heart disease Heart disease in ferrets usually results in congestive heart failure and can be due to a variety of causes. The same diagnostic techniques are used to diagnose the cause as with other species, including chest radiographs, echocardiograms, and electrocardiograms. The heart will be enlarged, but the reason for the enlargement depends upon the condition identified from these tests. The enlarged heart may be due to the following: dilated cardiomyopathy, where the heart walls are thin and the chambers are dilated; hypertrophic cardiomyopathy, where the heart walls are very thickened and the chambers are small as a result; valvular disease, where one or more of the heart valves is not functioning properly causing the heart to work harder; myocarditis, where the heart muscle is inflamed, preventing the heart from functioning properly; and heartworm disease, where the presence of worms within the chambers of the heart causes disruption of the blood flow and function of the heart. The cause of most of these conditions is not known, and the only one that can be prevented is heartworm disease (Antinoff et al., 2000).

TREATMENTS

Table 5.4 presents the formulary and drug dosages for ferrets.

Table 5.4

Formulary.

Agent

Dosage (mg/kg)

Route

Acepromazine

0.1–0.5

SC, IM

Amikacin

8–16 divided q8–24h

IM, SC, IV

Amitraz

0.3% q7d

Topical

Amoxicillin

10–30 q8–12h

PO

Amoxicillin/clavulanic acid

12.5–25 q8–12h

PO

Ampicillin

5–30 q8–12h

SC, IM, IV

Atropine

0.04

IM, SC, IV

Buprenorphine

0.01–0.03 q8–12h

SC, IM, IV

Carprofen

1 q12–24h

PO

Cephalexin

15–30 q8–12h

PO

Ciprofloxacin

10–30 q24h

PO

Clindamycin

5–10 q12h

PO

Cimetidine

10 q8h

PO, SC, IM, IV

Dexamethasone

0.5–2.0

IM, IV, SC

Diazepam

1–2

IM

Diphenhydramine

0.5–2.0 q8–12h

PO, SC, IM

Enrofloxacin

5–15 q12h

PO, SC, IM

Fenbendazole

20 q24h × 5 days

PO

Furosamide

2 q8–12h

PO, SC, IM, IV

Glycopyrrolate

0.01

IM

Griseofulvin

25 q12h

PO

Isoflurane

To effect

IH

Ivermectin

0.2–0.4 repeat in 14 days 0.05 q30d for heartworm prevention

PO, SC PO, SC

Ketaconazole

10–30 q12–24h

PO

Ketamine

10–50

IM

Ketamine + acepromazine

20–35(K) +0.2–0.35(A)

SC, IM

Ketamine + diazepam

10–20(K) + 1–2(D)

IM

Ketamine + medetomidine

5–8(K) + 0.08–0.1(M)

IM

Ketoprofen

1 q24h

PO, SC, IM

Medetomidine

0.1

IM, SC

Metoclopramide

0.2–1.0 q6–8h

PO, SC, IM

Metronidazole

15–20 q12h

PO

Morphine

0.5–5.0 q2–6h

SC, IM

Neomycin

10 q6–8h

PO

Oxymorphone

0.05–0.2 q8–12h

SC, IM, IV

Oxytocin

0.2–3.0 IU/kg

SC, IM

Prednisone

0.5–2.0 q12–24h

PO

Procaine penicillin G

40,000 IU/kg q24h

SC

Tetracycline

20–25 q8–12h

PO PO in drinking water

Trimethoprim sulfamethoxazole

15–30 q12h

PO, SC

Yohimbine

0.5

IM

From: Morrisey and Carpenter (2004). 71

72

Fluid administration Fluids can be administered subcutaneously, intraosseously in the proximal femur, or intravenously, preferably intravenously if the animal is ill. An indwelling intravenous catheter can be most easily placed in either the cephalic or lateral saphenous vein. Jugular vein catheters are more difficult to place and usually require anesthesia. Ferrets in hypovolemic shock can be treated with IV administration of crystalloids and colloids while being warmed. Initially an isotonic crystalloid such as Plasma-Lyte A is infused at 10–15 mL/kg. A 6% Hetastarch solution can then be administered at 5 mL/kg over 5–10 minutes. Maintenance crystalloids can be administered at 2 mL/kg per hour (mL/ kg/h) once the heart rate is stable and systolic blood pressure is >90 mmHg. Ferrets can be predisposed to pulmonary edema from volume overload, so they should be monitored carefully (Lichtenberger, 2005).

Nutritional support When most ferrets get sick, they usually require some form of nutritional support because they do not have much body fat. Depending on the severity of the disease, various methods can be used to provide nutritional support. Ferrets can be force-fed liquid diets by syringe in 5–10 mL increments 3–4 times a day. Meat-based soft foods for hospitalized cats and dogs can be used in addition to baby foods, liquid soy-based products, and high-energy pastes. These should only be given for a few days as they are not nutritionally complete for ferrets, but they can be used until the ferret will eat a more complete diet. If force-feeding does not work, an esophagostomy tube can be placed or total parenteral nutrition (TPN) can be provided as well (Quesenberry and Orcutt, 2004).

REFERENCES Antinoff, Natalie, Garner, Michael, and Burgess, Mark. 2000. A Review of Diseases of the Ferret. Exotic DVM 2(2): 33–40. Bell, Judith A. 2004a. Gastrointestinal Diseases: Part II. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents:

Exotic Small Mammal Care and Husbandry

Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 33–38. Bell, Judith A. 2004b. Periparturient and Neonatal Diseases. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 50–56. Brown, Susan A. 2004. Basic Anatomy, Physiology, and Husbandry. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 2–11. Burgess, Mark, and Garner, Michael. 2002. Clinical Aspects of Inflammatory Bowel Disease in Ferrets. Exotic DVM 4(2):29–34. Johnson-Delaney, Cathy. 2006. Ferret Adrenal Disease: 2006 Perspective. Exotic DVM 8(3):31–34. Kiefer, Kristina M., and Johnson, Dan. 2006. What Veterinarians Need to Know about Ferrets. Exotic DVM 8(2):38–43. Lichtenberger, Marla. 2005. Shock, Fluid Therapy, Anesthesia and Analgesia in the Ferret. Exotic DVM 7(2):24–30. Marini, Robert P., Otto, Glen, Erdman, Susan, Palley, Lori, and Fox, James G. 2002. Biology and Diseases of Ferrets. In Fox, J.G., Anderson, L.C., Loew, F.M., and Quimby, F.W. (eds.). Laboratory Animal Medicine. Second edition. Academic Press, San Diego, pp. 483–513. Morrisey, James K., and Carpenter, James W. 2004. Formulary. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 436–444. Quesenberry, Katherine E., and Orcutt, Connie. 2004. Basic Approach to Veterinary Care. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 13–23. Quesenberry, Katherine E., and Rosenthal, Karen L. 2004. Endocrine Diseases. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 79–89. Taylor, Bobbi. 2001. Alternate Technique for Venipuncture in Ferrets. Exotic DVM 2(6):37–39. Willard, Thomas R. 2002. Exotic Animal Nutrition: Ferrets. Exotic DVM 4(4):36–37.

6

Mice

Mice have been used in scientific research since the 1600s. The ability to create genetically engineered mice, as well as their small size, short generation time, and ease of breeding, have made mice the most widely used experimental animal (Suckow et al., 2001). Standard laboratory mice, Mus musculus, are usually white, but “fancy mice” or pet varieties are available in a multitude of varieties, including satin, long-haired, pied, and various solid colors (Bihun and Bauck, 2004). Mice can be good pets for older children, but may be too skittish for younger children to handle. They require little space and are relatively inexpensive to maintain. BASIC ANATOMY AND PHYSIOLOGY

Mice have physical characteristics typical of members of the order Rodentia. Typical body weight for an adult is 30 g, with males being larger than females. Mice are nocturnal and most often eat and engage in nesting and burrowing behaviors at night. Table 6.1 lists the basic biological parameters for mice. The dental formula of the mouse is 2(1/1 incisors, 0/0 canines, 0/0 premolars, and 3/3 molars). Their incisors continually erupt and will overgrow if malocclusion occurs. Mice have exophthalmic eyes. The Harderian gland is found within the orbit and produces secretions for ocular lubrication. The secretions contain porphyrins, which give the tears a red appearance. In stressed or diseased animals, increased tear production can be mis-

Table 6.1 Basic biologic parameters. Body weight

Adult male: 20–40 g Adult female: 18–35 g Birth weight: 1–1.5 g

Body temperature

36.5–38.0 °C (97.5–100.4 °F)

Reproductive data

Sexual maturity Female: 6 weeks Male: 6 weeks Estrous cycle: 4–5 days Gestation length: 19–21 days Litter size: 7–11 Weaning age: 18–21 days

Life span (captivity)

12–36 months

Heart rate

427–697 beats per minute

Respiratory rate

91–216 breaths per minute

Food intake

3–5 g/adult

Water intake

5–8 mL/adult

From: Bihun and Bauck (2004); Suckow et al. (2001).

taken for bleeding from the eyes (Bihun and Bauck, 2004). REPRODUCTION AND SEXING

Males are typically twice the size of females. Adult males can be distinguished from females by the presence of a scrotal sac containing the testes (Fig. 6.1). Rodents have open inguinal rings and can retract their testes into the abdomen. In young mice, sexing can be accomplished by comparing the anogenital distance, 73

74

Exotic Small Mammal Care and Husbandry

Fig. 6.2 Increased anogenital distance in male (left) than female (right) mouse.

Fig. 6.1 Differentiation of female (left) from male (right) external genitalia. For color detail, please see color plate section.

which is greater in males than in females (Fig. 6.2). Mice become sexually mature by 7–8 weeks of age. Females are polyestrous and cycle every 4–5 days. Mating is usually detected by the formation of a vaginal plug, which is a white mass that fills the vagina formed from secretions of the coagulating and vesicular glands of the male mouse. Gestation is typically 19–21 days, with an average litter size of 10–12 pups. The optimal weaning age in mice is 21 days. HOUSING AND HUSBANDRY

The choice of caging system should take into consideration ease of cleaning, ability to contain mice without escape, and ventilation. Although wire cages offer the benefit of good ventilation and climbing as enrichment, a small-gauge wire will be necessary to prevent escape. Aquarium-type cages are more secure

and allow for provision of deep bedding and nesting. Cage tops should be screened to secure mice. The optimal temperature range for mice is 64 °F to 79 °F (18 °C to 26 °C). Water bottles should be mounted and should be checked daily. Rodent food pellets can be provided in dishes kept on the floor to minimize contamination with feces and urine. There are many different types of bedding available, ranging from recycled paper to wood shavings. Cedar shavings have been shown to affect microsomal oxidative liver enzymes in rats and mice and potentially cause dermatological and respiratory effects (Bihun and Bauck, 2004). Environmental enrichment and exercise are important in captive mice. Exercise wheels, tunnels, nesting material, and exercise balls improve the quality of life for the pets and can promote human interaction and bonding. Most rodents have similar nutritional requirements. Formulated diets (pellets or blocks) are more nutritionally complete than seed diets, which are high in fat. A minimum protein requirement of 16% and fat content of 4%–5% is appropriate for a maintenance diet in mice. Breeding animals may require a protein content of up to 20%. Adult mice drink 6–7 mL of water per day. Decreased water consumption will decrease food consumption (Jacoby et al., 2002).

Mice

75

HANDLING AND RESTRAINT

Mice are very active and will run away when you try to capture them. The easiest way to immobilize them is to grasp them initially at the base of the tail. While still holding them by the tail, use the forefinger and thumb to gently pin down the head and grasp the “scruff” (loose tissue at the back of the neck). The rest of the body then can be cradled in the palm of your hand. Commercial restraint devices are available that allow for hands-free restraint (Fig. 6.3). Ideally, mice should be acclimated

Fig. 6.3 Commercial restraint device for mice.

to these devices over a period of time to minimize stress. PHYSICAL EXAM

Many diseases in small rodents are the result of improper husbandry or nutrition. Rodents should be examined in their home cages to evaluate water provision, food, bedding, and sanitation. General behavior and activity level in the cage should be observed. Findings such as ruffled fur or a hunched position can indicate illness. A thorough medical history is crucial to making a correct diagnosis. The information should include the source of the animal, primary caregiver, food preferences, duration of illness, and what other types of animals are in the household. Rodents should be weighed on a gram scale for accuracy. Gentle abdominal palpation can be performed to assess for masses and body condition. A small otoscope is helpful to evaluate the eyes, ears, and oral cavity. Incisor problems are common in small rodents. Respiratory and heart rates are difficult to measure in rodents. Normal physiologic parameters are listed in Table 6.1 (see section “Basic anatomy and physiology”). The coat should be evalu-

Table 6.2 Reference ranges for hematology and serum biochemical values for mice. Value

Reference Interval

RBC (×10 cells/μL)

7.9–10.1

Hemoglobin (g/dL)

11.0–14.5

6

Hematocrit (%) WBC (×103 cells/μL)

37–46 5.0–13.7

Neutrohphils (%)

10–40

Lymphocytes (%)

55–95

Monocytes (%)

0.1–3.5

Value Glucose (mg/dL)

73–183

Cholesterol (mg/dL)

59–103

Blood urea nitrogen (mg/dL)

18–31

Creatinine (mg/dL)

0.48–1.1

Aspartate aminotransferase (U/L)

101–214

Alaline aminotransferase (U/L)

Eosinophils (%)

0–4

Alkaline phosphatase (U/L)

Basophils (%)

0–0.3

Total bilirubin (mg/dL)

Platelets (×103 cells/μL) Total blood volume (mL/kg) Total protein (g/dL)

600–1,200 70–80 59–103

Reference Interval

Sodium (mmol/L)

44–87 43–71 0.3–0.8 143–164

Potassium (mmol/L)

6.3–8.0

Chloride (mmol/L)

105–118

Albumin (g/dL)

2.5–4.8

Phosphorus (mg/dL)

5.2–9.4

Globulin (g/dL)

0.6

Calcium (mg/dL)

4.6–9.6

From: Bihun and Bauck (2004); Suckow et al. (2001).

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Exotic Small Mammal Care and Husbandry

ated for hair loss, skin lesions, masses, or evidence of parasites. Special attention should be paid to the condition of the footpads and nails (Daviau, 1999). SAMPLE COLLECTION

Urine and fecal samples are easy to obtain in mice. It is a normal reflex for mice to urinate when picked up. The quantity is often sufficient for a dipstick analysis. Fecal samples can be evaluated by flotation and direct smear for evidence of intestinal parasites. Blood collection sites include the lateral saphenous vein, lateral tail vein, and maxillary “facial” vein. Retro-orbital blood collection is not recommended because of the potential to injure the eye. Cardiocentesis is reserved for terminal patients under anesthesia. As a general rule, 10% of the total blood volume can be withdrawn without adverse effects every 3–4 weeks. The blood volume of the average adult mouse is 2–2.75 mL. Reference ranges for hematological and biochemical values are presented in Table 6.2.

Fig. 6.4

Oral gavage technique in mice.

common endoparasites and ectoparasites, if detected, can be routinely treated with ivermectin, although this agent is not approved for use in these species.

DRUG ADMINISTRATION

Drug administration can be challenging in small rodents. Most therapeutic agents must be diluted with 0.9% NaCl prior to administration. In a hospital setting, medication can be administered by injection or oral gavage (PO). Because mice have a small muscle mass, subcutaneous (SC) or intraperitoneal (IP) injection is used most commonly. Therapeutic agents can be administered at home in food or drinking water. If not eating, oral medications can be administered by oral gavage using a bulb-ended metal feeding tube or flexible feeding tube (Fig. 6.4). PREVENTIVE HEALTH

Preventing disease in small rodents is usually more effective than treatment. Acquiring animals from reliable sources and providing optimal husbandry and nutrition will prevent most common diseases. No vaccines are routinely recommended for rodents. Many

COMMON DISEASES

Pet rodents may present with nonspecific clinical signs such as ruffled fur, a hunched appearance, reluctance to move, and anorexia. The most common diseases in mice are dermatopathies, enteropathies, and pneumonia (Donnelly, 2004). Table 6.3 presents the mouse formulary.

Gastronintestinal disease Diarrhea is uncommonly seen in pet mice, although it is sometimes associated with overfeeding green vegetables. Endoparasitic infections are common, but not clearly associated with clinical disease. Giardia muris and Spironucleus muris are pear-shaped, flagellated protozoan parasites found in the duodenum of young mice or immunocompromised adult mice. Infected animals may be asymptomatic or show signs of weight loss, rough haircoat, or abdominal distension. Diagnosis is based on the demonstration of trophozoites in fecal wet

Table 6.3 Mouse formulary. Agents

Dosage (mg/kg)

Route

Amikacin

10 q12h

SC, IM

Ampicillin

20–50 q12h

PO, SC, IM

Ciprofloxacin

10 q12h

PO

Doxycycline

5 q12h

PO

Enrofloxacin

5–10 q12h

PO, SC, IM

Gentamicin

5–10 q12h

SC, IM

Metronidazole

10–40 q24h

PO

Penicillin G

22,000 IU/kg q24h

SC, IM

Trimethoprim-sulfa

15–30 q12h

PO, SC

Griseofulvin

25 q24h

PO

Lime sulfur dip (2.5%)

Dip q7d for 4–6 treatments

Topical

Antimicrobial Agents

Antifungal Agents

Antiparasitic Agents Amitraz

1.4 mL/L q7d

Topical

Fenbendazole

20 q24h for 5 days

PO

Ivermectin

0.2–0.4 q10–14d

SC

Praziquantel

6–10 repeat in 10 days

PO, SC, IM

Sulfadimethoxine

10–15 q12h

PO

Sulfmerazine

1 mg/mL

Drinking water

Sulfaquinoxaline

1 mg/mL

Drinking water

Chemical Restraint, Anesthesia, Analgesia Acepromazine

0.5–1.0

IM

Atipamazole

1–2.5

SC

Atropine

0.1–0.4

IM, SC

Buprenorphine

0.05–2.5 q6–12h

SC, IP, IM

Butorphanol

1–5 q4h

SC

Carprofen

5–10

PO

Diazepam

3–5

IM

Flunixin meglumine

2.5 q12–24h

SC

Glycopyrrolate

0.01–0.02

SC

Ibuprofen

7–15 q4h

PO

Isoflurane

0.25%-4.0% to effect

Inhalation

Ketamine

22–44

IM

Ketamine + medetomidine

50–75 (K)/10 (M)

IP

Ketamine + xylazine

50 (K)/5 (X)

IP

Ketoprofen

5 q24h

SC, IM

Medetomidine

0.1

SC, IM

77

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Exotic Small Mammal Care and Husbandry

Table 6.3 Continued Agents

Dosage (mg/kg)

Route

Midazolam

1–2

IM

Morphine

2–5 q2–4h

SC, IM

Naloxone

0.01–0.1

SC, IP

Oxymorphone

0.2–0.5 q6–12h

SC, IM

Pentobarbital

50–90

IP

Cimetadine

5–10 q6–12h

PO, SC, IM, IV

Dexamethasone

0.5–2.0

IM, SC, IV

Diphenhydramine

1–2 q12h

PO, SC

Furosemide

2–10 q12h

PO, SC

Metoclopramide

0.2–1.0 q12h

PO, SC, IM

Oxytocin

0.2–3.0 IU/kg

SC, IM, IV

Prednisone

0.5–2.2

SC, IM

Miscellaneous Agents

From: Carpenter (2005); Morrisey and Carpenter (2004).

mounts. Metronidazole (0.04%-0.10% for 14 days) delivered in drinking water is usually effective at treating intestinal protozoal infections (Donnelly, 2004). Pinworm infection is common and considered nonpathogenic. The two species commonly diagnosed are Syphacia obvelata and Aspicularis tetraptera. Diagnosis of S. obvelata is made by evaluation of a Scotch tape prep of the perianal region to demonstrate ova, as adult worms deposit eggs around the anus. Aspicularis tetraptera ova can be found on a fecal float or direct smear. Mice are typically asymptomatic, but some animals will exhibit rectal prolapse. Treatment with ivermectin 2 mg/kg PO given twice at 10-day intervals has been shown to be effective at eliminating pinworm infection in mice. Tyzzer’s disease, caused by the gram-negative bacterium Clostridium piliforme, can infect mice resulting in clinical signs of lethargy, diarrhea, and death. Although not common in pet mice, this agent can affect many species, including rats, hamsters, and rabbits. Diagnosis is based on demonstration of the typical intracellular organisms in tissue sections of liver and intestine.

Helicobacteriosis is a common infection of laboratory mice. Helicobacter is a gram-negative spiral-shaped organism that has been isolated from the gastrointestinal tract of many mammals, including humans. Although mice are usually asymptomatic, infection can result in intestinal inflammation, diarrhea, and rectal prolapse. Effective treatment has been achieved with triple therapy with amoxicillin, metronidazole, and bismuth administered for 2 weeks. Salmonellosis can be spread by asymptomatic carriers. Infection is more common in young mice and can result in septicemia and death. Clinical signs include lethargy, weight loss, abdominal distension, and death. Salmonella has the potential for zoonotic infection and it is recommended that affected animals be euthanized.

Respiratory disease Respiratory disease is common in mice and rats. Mycoplasmosis pulmonis is a gram-negative bacterium that is responsible for murine respiratory mycoplasmosis (MRM). Clinical signs include suppurative rhinitis, otitis media, and chronic pneumonia. “Chattering” and

Mice

79

dyspnea can be observed in affected mice. Animals that survive typically develop chronic infections. Sendai virus is a paramyxovirus related to human parainfluenza virus 1 (Jacoby et al., 2002). Infected mice exhibit weight loss, dyspnea, “chattering,” and crusting of the eyes. Sendai virus is transmitted by aerosol and is highly infectious. Neonates typically do not survive. Adult mice may develop secondary opportunistic infections.

Neurological diseases Lymphocytic choriomeningitis virus (LCMV) is widely distributed in North and South America. Wild mice are the reservoir for infection. Infected mice can exhibit neurological forms of disease (head tremors, seizures, death) or visceral forms of disease (glomerulonephritis). Although uncommon in pet mice, this agent is important because it can infect people and cause mild to serious or fatal disease (Suckow et al., 2001).

Dermatological disease Diseases of the skin are commonly seen in pet mice. Mice establish a social hierarchy when housed in groups and engage in fighting and barbering. The dominant mouse will nibble the whiskers and hair around the face from the submissive cage mates (Fig. 6.5). Fur mites typically infest the head, neck, and shoulder area, causing pruritis, patchy alopecia, and ulceration. The following three species are most common: Myobia musculi, Myocoptes musculinus, and Radfordia affinis. Identification of mites or eggs on skin scrapings is diagnostic. Mites are spread by direct contact with infected mice or bedding. Treatment with ivermectin (0.2 mg/kg SC or PO) twice at 10day intervals is effective. Skin swellings may be caused by abscesses or neoplasia. In group-housed animals, bite wounds can become secondarily infected with various opportunistic pathogens, including Staphylococcus aureus, Pasteurella pneumotropica, and Streptococcus pyogenes. Fine needle aspirate will demonstrate a mucopuru-

Fig. 6.5 Barbering in mice. For color detail, please see color plate section.

lent exudate. The most common subcutaneous tumor in mice is mammary adenocarcinomas. In some strains of mice, the incidence is as high as 70% (Donnelly, 2004). REFERENCES Bihun, C., and Bauck, L. 2004. Basic Anatomy, Physiology, Husbandry, and Clinical Techniques. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 286–298. Carpenter, J.W. 2005. Exotic Animal Formulary. Third edition. Elsevier Saunders, St. Louis, MO, pp. 377–408. Daviau, J. 1999. Clinical Evaluation of Rodents. Veterinary Clinics of North America: Exotic Animal Practice 2(2): pp. 429–445. Donnelly, T.M. 2004. Disease Problems of Small Rodents. In Quesenberry, K.E., and Carpenter, J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 299–315.

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Jacoby, R.O., Fox, J.G., and Davisson, M. 2002. Biology and Diseases of Mice. In Fox, J.G., Anderson, L.C., Loew, F.M., and Quimby, F.W. (eds.). Laboratory Animal Medicine. Second edition. Academic Press, San Diego, CA, pp. 35–120. Morrisey, J.K., and Carpenter, J.W. 2004. Formulary. In Quesenberry, K.E., and Carpenter,

Exotic Small Mammal Care and Husbandry

J.W. (eds.). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. Second edition. Saunders, St. Louis, MO, pp. 436–444. Suckow, M.A., Danneman, P., and Brayton, C. 2001. The Laboratory Mouse. CRC Press, Boca Raton, FL.

Fig. 4.1 Proper rabbit manual restraint.

a Fig. 4.3

Fig. 4.2 Mandibular prognathism and malocclusion. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

b a External genitalia of a female rabbit.

Fig. 4.3 b External genitalia of a male rabbit.

Fig. 5.1 Normal ferret (copyright Eric Isselée, Dreamstime.com).

Fig. 5.5 Manual restraint of a ferret while distracting with Nutri-Cal. CP-1

Fig. 5.7 Typical alopecia pattern associated with adrenal disease in ferrets. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 6.1 Differentiation of female (left) from male (right) external genitalia.

Fig. 6.5

Barbering in mice.

Fig. 7.2

Fig. 7.11 stress. CP-2

Albino rat.

Rat with porphyrin staining due to

Fig. 7.6 Rat housed on corncob bedding with paper towel added for enrichment. Notice how the paper towel has been shredded into small pieces.

Fig. 7.9 Blood collection from the saphenous vein.

Fig. 8.1 Pofile of a normal gerbil. (Copyright Eric Isselée, Dreamstime.com.)

Fig. 8.2 Gerbil abdomen with ventral gland located centrally. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 8.4 Degloved tail tip of gerbil. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

CP-3

Fig. 9.1 Normal hamster in cage. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 9.3 Isolated hamster cheek pouch. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 9.7 Female gerbil with a litter of pups. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 9.9 Hamster in tubing enrichment device. (Copyright Alina Cardiae, Dreamstime.com.)

b Fig. 10.1 b Abyssinian guinea pigs. (Copyright Stefan Andronache, Dreamstime.com.) a Fig. 10.1 a Coat color variation in guinea pigs. CP-4

Fig. 10.5 Ulcerative pododermatitis in a guinea pig. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 10.6 Trixacarus caviae infection. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 11.1 The most common pet species, Chinchilla laniger. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 11.8 Fur ring removed from a male chinchilla. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 12.1 Profile of a normal degu. (Copyright Daniel Rajszczak, Dreamstime.com.)

Fig. 11.9 Fur slip in a chinchilla. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.) CP-5

Fig. 12.2 Ventral abdomen of female (left) and male (right) degu genitalia. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 12.5 Degloved tail of a degu requiring surgical correction. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 13.2 Balled-up hedgehog. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 13.4 Self-anting (anointing). (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

CP-6

Fig. 14.1 Sugar glider. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 13.8 Obese hedgehog. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

Fig. 14.3 Sugar glider grasping plant. (Photo courtesy of Judi Fox.)

Fig. 14.9 Sugar glider enrichment. (Photo courtesy of Judi Fox.)

CP-7

Fig. 14.10 Sugar glider in nest box. (Photo courtesy of Dan H. Johnson, DVM, Avian and exotic Animal Care, Raleigh, NC.)

Fig. 15.1 Adult Didelphis virginiana. (Copyright Teekaygee, Dreamstime.com.)

Fig. 15.2

CP-8

Juvenile Didelphis virginiana.

Fig. 15.4 Abdominal pouch with litter. (Photo courtesy of Dan H. Johnson, DVM, Avian and Exotic Animal Care, Raleigh, NC.)

7

Rats

The rat (Rattus norvegicus) is a common pet belonging to the order Rodentia and the family Muridae. Rats are thought to have originated in the areas now known as southern Russia and Northern China. There are over 130 species in the genus Rattus, although the two most prominent are the black rat and the brown rat (Kohn and Clifford, 2002). The black rat (R. rattus) was well-known in Europe by 1100 AD and the brown rat (R. norvegicus) was a common occurrence in Europe by the 1700s. Rats are good pets for children because they are large enough to be easily handled, are non-aggressive, are social, are easily trainable, and rarely bite. Rats are also intelligent and affectionate, thus adding to their desirability as a pet species.

Fig. 7.1

Hooded rat.

COMMON BREEDS

Orr (2002) describes five types of fancy rats bred in the United Kingdom: self (one solid color), marked (Irish, Berkshire, Hooded, Capped), silver (recognized self-color containing equal numbers of nonsilver and silver guard hairs), any other variety (Siamese, Agouti), and rex (coat is evenly curled and there are as few guard hairs as possible). In the United States the most common pet rat species is R. norvegicus, with the hooded (Fig. 7.1) and white (Fig. 7.2) rat being the most frequent color variations (Tully, 2008). Albino rats tend to be calmer than hooded rats, which are more likely to be aggressive (Leck, 1999).

Fig. 7.2 Albino rat. For color detail, please see color plate section. 81

82

Exotic Small Mammal Care and Husbandry

BASIC ANATOMY AND PHYSIOLOGY

Rats are nocturnal and are characterized by elongated body shape, small eyes and ears, short fur, and hairless tails. Their long tail may comprise up to 85% of the total body length. The tail is generally longer in the female than in the male and is useful in maintaining balance and thermoregulation. The body is covered with hair except on the nose, lips, palms of forelimbs, and soles of hind limbs. There are two types of hair: guard hairs, which have a long shaft, and under hairs, which do not have a long shaft. The hair grows in a cyclical pattern with hair growing in length for 17 days then resting for 17 days (Kohn and Clifford, 2002). Rats also have specialized tactile hairs called vibrissae that are used in sensory input. As rats get older the white hair coat can turn a yellowish color. Rat eyes are bulging, the eyelids are well developed, and the only visible structure is the cornea (Kohn and Clifford, 2002). Albino rats, as are other albino animals, are inclined toward poor eyesight. Rats have a lacrimal gland located behind the eyeball, called the Harde-

Fig. 7.4

Male rat.

rian gland (Leck, 1999). This gland produces a porphyrin secretion that is red in color. These secretions tend to be produced when the rat is stressed or ill. Each limb has five digits with a nail. Rats have open inguinal canals, a divided stomach, a large cecum, a diffuse pancreas, and an os penis.

Fig. 7.3

Rat teeth. (Courtesy of Ian Thomas.)

Fig. 7.5

Female rat.

Rats

Rats are omnivores and have one permanent set of teeth. The teeth grow continuously (Fig. 7.3) and must be worn down by chewing and gnawing. The dental formula is 2(1/1 incisors, 0/0 canines, 0/0 premolars, 3/3 molars). Malocclusion may occur if the incisors are misaligned and cannot be sufficiently worn down by normal gnawing activities. REPRODUCTION AND SEXING

It is fairly easy to distinguish gender in rats as the distance between the anus and the genital opening, called the anogenital distance, is about twice as long in the male as in the female (Figs. 7.4 and 7.5). Males have a distinct scrotum located between the anus and the prepucial opening, although the testicles can be retracted into the abdomen. Only female rats possess nipples. The presence of a copulatory plug formed by semen coagulation indicates mating has occurred. The estrous cycle lasts 4–5 days and contains distinct components: proestrus (∼12 hours duration), estrus (∼12 hours duration), metestrus (∼21 hours duration), and diestrus (∼57 hours duration) (Sharp and LaRegina, 1998). Parturition lasts about 90 minutes and a post-partum estrus occurs with about 50% fertility. Breeding system can be either a monogamous pair or a polygamous group consisting of one male housed with up to six females. Litter size is from 3 to 18 pups depending on species. Rats are generally weaned at 20–21 days of age. (Table 7.1 gives the basic biological parameters of rats.) UNIQUE FEATURES OF IMPORTANCE

Rats have brown fat, which plays a role in thermogenesis during exposure to the cold. This fat is distributed throughout the ventral, lateral, and dorsal aspects of the neck but is primarily found between the scapulae. Brown fat is often confused with salivary glands or lymph nodes. The rat does not have a gall bladder nor does it have the ability to vomit, due to the presence of a limiting ridge at the junction of the stomach and the esophagus. Rats, like other rodents, do not have sweat glands, cannot

83

Table 7.1 Basic biologic parameters. Body weight

Adult male: 450–520 g Adult female: 250–400 g Birth weight: 5–6 g

Length

Body: 23–28 cm (9–11 inches) Tail: 18–23 cm (7–9 inches)

Body temperature

35.9 °C–37.5 °C (96.6 °F–99.5 °F)

Reproductive data

Sexual maturity Female: 40–65 days Male: 40–65 days Estrous cycle: 4–5 days Duration of estrus: 13–15 hours Female continuously polyestrous Postpartum estrus Gestation length: 20–23 days Litter size: 3–18 Weaning age: 21 days Breeding life: 14 months

Life span (captivity)

2–4 years

Heart rate

250–600 beats per minute

Respiratory rate

66–150 breaths per minute

Food intake

20–60 g/day

Water intake

15–30 mL/day

From: Bistner et al. (2000); Kahn (2007); Lawson (2001); Sharp and LaRegina (1998).

pant, and are poor regulators of core body temperature although they can dissipate heat through their ears and tails (Bihun and Bauck, 2004). The tail vessels can vasoconstrict when heat conservation is necessary and can vasodilate to dissipate heat. Rats adapt more readily to cold temperatures than to heat. Rats have poor vision and cannot detect color. Rats, as other rodent species, are coprophagic. HOUSING AND HUSBANDRY

Rats tend to be social but can do well when housed in small groups or singly. Unlike mice, adult males can be housed together with few problems. Cages should be large enough to allow the rats to nest, burrow, and exercise. Cages should be easy to clean as poor husbandry practices can lead to disease conditions.

84

Rat cages should be escape-proof and constructed of a material that is not easily chewed. Cage sides could be constructed of wire or metal mesh, Plexiglas, or plastic. An open screen top is suggested for solid-walled enclosures to help aid in ventilation and to prevent escape. If the household contains other pets such as cats, dogs, or ferrets, the enclosure may require a sturdier top to ensure the rats’ safety. Leck (1999) recommends housing for each adult rat should be at least 24″W × 24″L × 12″H. Because rats like to climb, a cage that is taller than the recommended height and fitted with ramps and ropes would be preferred. Bedding can consist of recycled paper products, hardwood chips or shavings, or shredded paper (Fig. 7.6). Pine and cedar bedding should not be used as it can affect liver enzymes. Bedding should be approximately ¼″ to 1” deep and should be changed several times a week. Ideal room temperatures should be between 65 °F and 80 °F (18–26 °C) and relative humidity should be maintained between 40% and 70%. Cages should be located away from windows and drafts to avoid extreme temperature fluctuations. NUTRITION

Exotic Small Mammal Care and Husbandry

diet is that the rat can select the palatable seeds and ignore the less desirable seeds; therefore, a balanced diet is not achieved and obesity is likely to occur. Rodent diets that are in the form of pellets or blocks are recommended because they provide a more uniform diet. Commercial diets are readily available that meet the rat’s nutritional requirements. Fresh vegetables and fruits can be added to the diet in small amounts. Adult rats need 5–10 g of pellets per 100 g of body weight daily. Water should be provided ad libitum via drinking bottle with sipper tube, although rats generally only drink 10 mL of water per 100 g of body weight daily.

ENRICHMENT

Rats, like other rodents, can benefit from having objects in their environment they can manipulate. Objects that provide for the normal activities of burrowing and gnawing are ideal. These objects include wooden blocks, balls, shredded paper,