Exotic mammal dermatology (Proceedings)


Exotic mammal dermatology (Proceedings)

Apr 01, 2009

When an exotic small mammal presents for a problem associated with the integument, it may be hard not to try to focus on that specific system. However, it is important for veterinarians to remember that many of the exotic small mammals presenting to their practices often have multiple medical problems. Therefore, a complete and thorough history and physical examination should be performed to develop a complete problem list for the patient. When collecting a history, the questions should focus on obtaining details of the animal's exact husbandry standards, including enclosure size, environmental temperature and humidity, type of substrate and cage furniture, lighting, diet, and sanitation protocol. The physical examination should be performed in a stepwise manner to ensure that every body system is evaluated. The author prefers to start with the head and work caudally.

In the past, many dermatologic conditions in exotic mammals were treated empirically. However, veterinarians are now realizing that managing these cases requires a thorough diagnostic work up. A diagnostic plan for a dermatological condition in an exotic small mammal should follow the standard protocols described for domestic species, including hematology, radiography, microbiology, cytology, and surgical biopsy. A complete blood count should be performed to assess the patient for an inflammatory disease. Radiographs can be performed to assess the extent of an integumental injury. This is especially important if a secondary osteomyelitis is suspected. A skin scrape and cytology can be a very useful diagnostic tool when evaluating a skin lesion. The results of the cytology may be used to guide sample submissions for culture (e.g., bacterial or fungal or both). Full thickness surgical biopsies may also be required to confirm a diagnosis. Biopsies should be collected from the margin of the lesion and include both healthy and affected tissues. Multiple samples may need to be collected to confirm a diagnosis.

Abscesses are a common finding in captive exotic small mammals. Bacterial infections are the most common etiology associated with abscesses in the author's practice, although fungal organisms, foreign bodies, and parasites have also been associated with abscess formation in these animals. Rabbit and rodent abscesses tend to be well-defined, caseous masses. Because of the caseous nature of the abscesses, topical or systemic antimicrobials alone have limited value for treatment. S urgical removal of the abscess in addition to antimicrobials is generally required to successfully manage these cases. A cytological exam of the abscess material should be made to determine the nature of the abscess. Bacterial or fungal cultures should be submitted based on the cytological findings. Antimicrobial selection should be based on an antimicrobial sensitivity profile.

Ectoparasites are a common finding on recently imported exotic small mammals, and captive species housed outdoors or in close approximation to domestic pets. Most species of mites and lice are species specific, whereas fleas and ticks are not. Special precautions, such as wearing exam gloves, should be taken when working with these species to prevent the spread of potentially zoonotic pathogens. Diagnosis of an ectoparasite infestation can be made during a thorough physical examination. Many of the larger ectoparasites can be readily identified with the naked eye, whereas further diagnostics, such as a tape preparation or skin scrape, are required to identify microscopic ectoparasites.

Ear mites are one of the most common parasites observed in the author's practice. Otodectes cynotis is the ferret ear mite. Affected ferrets generally have dark ceruminous wax within the external ear canal and may frequently scratch at their ears. Psoroptes cuniculi is the rabbit ear mite. This mite can cause severe inflammation and crusting of the external ear canal. Rabbits with P. cuniculi may have painful ears, so a clinician should exercise caution when manipulating the ears. Diagnosis can be made on cytological examination. Ivermectin (0.2-0.4 mg/kg q 2 weeks for 3 treatments) is an effective treatment for ear mites.

The rabbit fur mite, Cheyletiella parasitovorax, is an infrequent finding in pet rabbits. Infested rabbits look as if they have "walking dandruff". Diagnosis can be made from a skin scrape or acetate tape preparation. The life cycle of this parasite is approximately 35 days. Ivermectin (0.4 mg/kg q 2 weeks for 3 treatments) is the treatment of choice.

Sarcoptic mange, caused by Sarcoptes scabei, affects many mammalian species. Affected animals often develop severe, intense pruritus, scales, crusts, erythema, and generalized alopecia. Pododermatitis and self-mutilation are common findings in ferrets. Humans that become infested with sarcoptic mange may develop wheals, vesicles, papules, and intense pruritus. Infected animals should be quarantined from other animals and only handled with gloves, to reduce exposure. Lime sulfur shampoos, ivermectin, and selamectin may be used to treat affected animals.

Chorioptes sp. is a common ectoparasite of African hedgehogs. Affected animals may present with crusty skin and spine loss. Microscopic examination of a skin scraping will confirm diagnosis. The mites can be eradicated by giving the animal three treatments of ivermectin (0.2 mg/kg) at two-week intervals.

Trixacarus caviae is the common mite of the guinea pig. In general, guinea pigs infested with T. caviae are asymptomatic. However, animals that are maintained in poor conditions or are stressed may develop generalized clinical signs, including alopecia, intense pruritus, scales, crusts, and hyperkeratosis. Pet owners, especially children, may become infected with T. caviae from direct contact with infected guinea pigs. Affected individuals generally develop mild dermatitis. Trixacarus caviae is difficult to eliminate in guinea pigs. Intensive environmental cleaning and treatment using ivermectin or selamectin has been found to be effective.

Rabbits housed outdoors are susceptible to Cuterebra spp. infestation. These large obligate parasites are generally found in the subcutis of rabbits. Affected rabbits will present with swelling(s) in the cervical, axillary, inguinal regions. These larval swellings have a characteristic air hole associated with them. Treatment can be accomplished by surgical removal of the larvae. The procedure can be performed using a local anesthetic (lidocaine) or under general anesthesia. Blunt dissection may be used to enlarge the air hole and extract the parasite.

Fleas (Ctenocephalides spp.) are a frequent finding on ferrets and rabbits housed outdoors or in households where domestic species have access to the outdoors. Management of flea infestations in exotic pets should be two-fold, treating both the environment and the animal. Flea sprays and powders that are safe for puppies and kittens are generally safe for ferrets and rabbits too. Imidacloprid (Advantage, Bayer, Shawnee Mission, KS) and lufenuron (Program, Novartis, Greensboro, NC) have both been used to eliminate fleas in ferrets and rabbits. Fipronil (Frontline, Merial, Duluth, MN) has been used in ferrets, but is not recommended for rabbits.

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