Small Mammal Medicine 101
World Small Animal Veterinary Association World Congress Proceedings, 2013
David Vella, BSc, BVSc (Hons), DABVP (Exotic Companion Mammal Practice)
Sydney Exotics & Rabbit Vets, Crows Nest, NSW, Australia

Introduction

The advancement of veterinary care of exotic companion mammals (ECM) is commensurate with that of canine and feline disciplines. Engaging in veterinary care of ECMs allows a practitioner to work with a wide range of species with varied anatomical and physiological types. Familiarity of each species' biology is paramount to practicing good medicine.

What Species Are Seen In Practice?

The main species seen include rabbits, ferrets and rodents (guinea pigs, chinchillas, rats, mice, hamsters, gerbils). Examples of other less common species include hedgehogs, sugar gliders, primates, and marsupials.

Bringing the ECM to the Consultation

Apart from small rodent species, which may sometimes be transported within their own cage, most ECMs require transport within a safe and secure pet/cat carry box. Many of these species will readily escape if given a chance and may subsequently be vulnerable to injury and difficult to recapture.

The ECM Consultation

A thorough history taking and assessment of husbandry is one of the most important aspects of the ECM consultation. A sound knowledge of each species' individual requirements is necessary in order to scrutinize each situation. A thorough investigation of the animal's husbandry, diet and medical history should be explored. Inappropriate diet is an especially common cause of disease in ECMs.

Most consultations can be performed with few specialized instruments. A good light source and magnification can become useful, as is a digital weighing scale able to measure to the nearest gram. Oral examination in rabbits and rodents is very important due the relatively high rates of dental disease in these species. Oral examination can be aided by the use of human bivalve nasal speculum (Welch Allyn).

ECM Handling

Some species and individuals are more readily able to be handled than others. It is important to portray a confident ability to handle these species in a consultation setting.

Rabbits

Towels play an important part in handling by providing a slip-free surface and an ability to snugly wrap and restrain 'burrito-style' a rabbit patient. There are several methods for holding/restraining rabbits, including head coverage, lumbar holds and 'C' positioning. It is important to carefully and safely restrain rabbits, as they harbor the ability to kick their hindlimbs with enough force to fracture their spine (usually secondary to lumbar hyperextension).

Ferrets

Whilst the majority of ferrets do not bite, their ability to do so should be kept in mind. Ferrets are often wriggly patients to examine and for some part of the examination (especially oral examination), a gentle but firm scruffing of the neck may serve to quieten the ferret and enhance inspection. Many ferrets will also open their mouths voluntarily once scruffed.

Rodents

Larger rodents, like guinea pigs and chinchillas, may also benefit from assisted towel restraint. Smaller rodents can usually be held in cupped hands. Always be careful with holding small rodents (e.g., mice, gerbils) by the tail, as degloving and other injuries may ensue.

ECM Examination

ECMs should be examined in a systematic way. There are several ways to carry this out, although maintaining a routine may be beneficial. Oral examination is very important, especially in rabbits, guinea pigs, and chinchillas. Both direct and indirect ophthalmic examinations can be performed. Conduct thoracic auscultation. Heart rates can be too fast to count in many ECM species. Abdominal palpations should be carried out carefully. Measurement of rectal temperatures can be performed in rabbits, larger rodents and some ferret patients. Always confirm gender in ECMs, as they are not uncommonly mistaken by the owner!

Body weight and body condition should be assessed and scored for every patient. It is necessary to become familiar with what constitutes each species 'normal' body condition. ECMs are frequently encountered in overweight and obese body conditions. Initial body weight measurement of a patient becomes a valuable reference point for future treatment plans. Accurate body weights are also necessary for accurate drug dosing.

ECM Therapeutics

There are few pharmacokinetic studies that have been performed on ECMs. Much information on drug use is derived empirically or extrapolated from other species. The common routes for medication delivery include subcutaneous, intravenous, intramuscular, and per os. Other routes can include topical/transdermal, intraperitoneal and aerosol.

There are some important species specifics that need to be considered, especially in respect to antibiotic use. Hindgut fermenters, such as rabbits and guinea pigs, are vulnerable to dysbiosis (imbalance of intestinal flora) secondary to inappropriate antibiotic administration for example.

Antibiotics

It is important to highlight some of the drug contraindications within the ECM range. Appropriate antibiotic use is of prime consideration. Rabbits and guinea pigs are especially sensitive to caecal dysbiosis and possible death with inappropriate antibiotic use. Antibiotics to avoid in these species include the lincosamides, beta-lactams, and the majority of the macrolides. Some beta-lactams may be tolerated parenterally in rabbits. In rodents, the following antibiotic contraindications are noted:

 Mice: streptomycin and procaine are toxic

 Rats: nitrofurantoin causes neuropathologic lesions

 Gerbils: streptomycin and dihydrostreptomycin are toxic

 Hamsters: (similar to guinea pigs) develop clostridial enterotoxaemia if given penicillins, erythromycin, lincomycin. Dihydrostreptomycin is lethal to hamsters.

Analgesics

The importance of offering appropriate analgesia in ECMs cannot be overemphasized. Providing adequate pain relief is important from a welfare, medical and ethical perspective. There are documented pain control methods from laboratory animal practices that can be used in the clinical setting for pet ECMs. However, the safety and pharmacology of many analgesics have not been scientifically evaluated for all species. Reducing pain can have positive effects on patient recovery, wound healing, and reducing morbidity. Returning to normal physiological status post-operatively, for example, is of relatively greater importance in ECMs due to their higher metabolic rates and more immediate need for food intake. A reduced food intake can more quickly lead to negative metabolic effects, such as hepatic lipidosis, hypoglycemia, and gastrointestinal stasis. The range of analgesics used in ECMs is on a par with canine/feline medicine and includes opioids, nonsteroidal anti-inflammatories (NSAIDs), local anesthetics, NMDA antagonists, alpha-2 adrenergic agonists, and gabapentin. It is important to note that NSAIDs especially are relatively well tolerated in rabbits and most rodents and required doses are higher than those used with dogs and cats; for example, the dose of meloxicam in rabbits is > 0.3 mg/kg q12h and in mice can be up to 5 mg/kg PO q24h.

Other Important Drugs in ECMs

Glucocorticoids

Some ECM species, especially rabbits, may be very sensitive to the effects of corticosteroids. They have been implicated as causes of immunosuppression and liver toxicity. The effects of glucocorticoids in such species are a highly controversial topic at present. This same 'sensitivity' to corticosteroids has also been suggested to occur in guinea pigs and other smaller rodents. Although there may theoretically be some usefulness in the potent anti-inflammatory effects of corticosteroids, it may be important to keep in mind the potential for immunosuppressive side effects. Ferrets are an exception to this, displaying a relatively higher tolerance to the negative side effects of this class of drug. In ferrets, glucocorticoids are used regularly in treating common conditions, such as insulinoma and lymphoma.

Fipronil

The use of fipronil (Frontline, Merial) in rabbits has been associated with causing death in this species. Death may be preceded by seizures. Fipronil should not be used in rabbits.

Zolazepam/Tiletamine

This combination is contraindicated in rabbits due to its association with nephrotoxicity and should not be used.

Fluid Therapy in ECMs

The indications and principles for fluid therapy in ECMs are similar to those in dogs and cats. The application of similar guidelines, such as estimating fluid deficit, maintenance requirements and ongoing losses should be determined. 'Surgical' rates of fluid administration can also be followed. All fluids should be given warm. Fluids can be warmed prior to administration by heating the fluids in the bag/syringe or in the fluid line. Commercial fluid line warmers can also be utilized.

Fluid requirements vary between ECM species and for some species have not been determined. Examples of daily maintenance fluid requirements (mL/kg/day) for guinea pigs, rabbits and mice are 100, 120 and 150 respectively.

Suitable crystalloid fluids (ideally based on packed cell volume, total solids, electrolyte, etc. measurement) include Plasma-Lyte 148 (Baxter Healthcare), lactated Ringer's solution (e.g., Hartmann's solution, Baxter Healthcare), or normal saline (0.9% NaCl, Baxter Healthcare). Dextrose solutions can be added to other crystalloids if patients are found to be hypoglycemic. Colloids, such as Gelofusine® (Braun), can be given in titrated doses of 5 mL/kg IV infusions over 5-10 minutes (especially if systolic blood pressure [SBP] can be measured and is suboptimal (< 90 mm Hg). As relatively small fluid delivery volumes are required, low-volume infusion systems are required. Examples include the NIKI V4 Volumetric Infusion Pump and syringe drivers (Terufusion® Syringe Pump STC527).

Typical parenteral fluid routes include intravenous (cephalic, saphenous, jugular, marginal ear, and lateral tail veins) and intraosseous (tibia and femur). For patients that are not considered clinically compromised or estimated to be less than 5% dehydrated, then subcutaneous (SC) fluid therapy may be used. The very loose skin over the shoulders and back can be utilized for this purpose. Intraperitoneal (IP) routes can also be used, but must be conducted with caution to avoid damage to abdominal viscera.

Assist Feeding ECMs

Assist feeding plays a crucial role in the supportive care and medicine of ECMs. The majority of these species have relatively high metabolic rates; hence, energy provision can be crucial to their recovery. Further to this issue are the hindgut fermenter species, which also require a fairly constant supply of nutrition to ensure adequate gastrointestinal health. Compared to canine/feline medicine, the provision of nutritive support may be required at a relatively earlier period in medical management. Fortunately, nowadays there are commercial products especially formulated for providing nutritional support to ECMs. These products come in a powder form that can be mixed with water and delivered via oral syringe feeding or via the placement of nasogastric/nasoesophageal feeding tubes (e.g., Oxbow Critical Care Feeding Formula and Carnivore Care [www.oxbowanimalhealth.com] and the Emeraid® range [Herbivore, Omnivore and Carnivore, www.lafebervet.com/]).

Clinical Techniques and Diagnostics

Apart from faecal examination for parasitology and microbiology, another important diagnostic tool is blood biochemistry, hematology, and urinalysis. Blood collection can be challenging in some patients due to size and vessel access. A safe blood collection volume is up to 1% of body weight. Typical blood collection sites for various species are dependent on the status of the patient and blood volume required. In many instances patients require sedation or anesthesia for collection purposes. Typical sites utilized are: rabbits (lateral saphenous, jugular, and cephalic veins), ferrets (cranial vena cava, lateral saphenous, jugular, and cephalic veins), rodents (cranial vena cava, lateral saphenous, cephalic, and lateral tail veins, ventral tail artery).

Urine may be collected as voided samples or cystocentesis (preferably ultrasound guided). Other useful standard diagnostic aids include radiography, ultrasonography, endoscopy, serology, molecular diagnostics, endocrinology, cytology/histology, and microbiology.

References

References are available on request

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

David Vella, BSc, BVSc (Hons), DABVP (Exotic Companion Mammal Practice)
Sydney Exotics & Rabbit Vets
Crows Nest, NSW, Australia


MAIN : Exotics/Wildlife : Small Mammal Medicine
Powered By VIN

Friendly Reminder to Our Colleagues: Use of VIN content is limited to personal reference by VIN members. No portion of any VIN content may be copied or distributed without the expressed written permission of VIN.

Clinicians are reminded that you are ultimately responsible for the care of your patients. Any content that concerns treatment of your cases should be deemed recommendations by colleagues for you to consider in your case management decisions. Dosages should be confirmed prior to dispensing medications unfamiliar to you. To better understand the origins and logic behind these policies, and to discuss them with your colleagues, click here.

Images posted by VIN community members and displayed via VIN should not be considered of diagnostic quality and the ultimate interpretation of the images lies with the attending clinician. Suggestions, discussions and interpretation related to posted images are only that -- suggestions and recommendations which may be based upon less than diagnostic quality information.

CONTACT US

777 W. Covell Blvd., Davis, CA 95616

vingram@vin.com

PHONE

  • Toll Free: 800-700-4636
  • From UK: 01-45-222-6154
  • From anywhere: (1)-530-756-4881
  • From Australia: 02-6145-2357
SAID=27