Close this window to return to IVIS www.ivis.org Proceeding of the LAVC Latin American Veterinary Conference Oct. 16-19, 2009 Lima, Peru Reprinted in the IVIS website with the permission of the LAVC http://www.ivis.org/
Dra. Geraldine Diethelm-Mader RABBIT MEDICINE: A BASIC APPROACH TO VETERINARY CARE COMMON SMALL MAMMAL EMERGENCIES LIGHT THERAPY HOLISTIC TREATMENT OF WILDLIFE AND RESCUE ANIMALS Página 269
COMMON SMALL MAMMAL EMERGENCIES General Conditions Trauma Trauma is a frequent cause for visits to the veterinarian by small animal owners. Not uncommonly, these pets are owned by small children, and it is not an infrequent occurrence for these little pets to get dropped, stepped on or bitten by dogs and cats. The approach should be no different than for any trauma victim. Treat life threatening emergencies first. Follow the ABC's, Airway, Breathing and Circulation. Attend to hemorrhage. Place the animal in a warm oxygen cage. Treat for shock with fluids. A balanced electrolyte at 90 ml/kg wither IV, IO, IP or SC. Antibiotics as needed. When stable, address fractures and lacerations. Ectoparasites Ectoparasites in small mammals are not an uncommon finding in private veterinary practice. Regardless of the location or the situation, these pests can represent a great disease problem, both as vectors of other infectious organisms, and as primary disease agents themselves, as most ectoparasites can cause anemia, pruritus, dermatitis and death. Diagnosis of the majority of the ectoparasites is simple, as most the arthropods are visible to the unaided eye, and are easily identified on physical examination. The Prostigmatid mites (such as Demodex spp.) have a more selective host range and may burrow under the skin, not always showing obvious clinical signs, and may require skin scrapings or biopsies to identify. The common flea, Ctenocephalides spp., is a frequent finding in most small mammals, including rabbits, ferrets and guinea pigs, where it can cause irritation, pruritus, dermatitis and anemia. Flea combs, permethrin dust and shampoos are useful in ridding the parasites. In individual pets mites can be managed efficiently if the owner is compliant. Eliminating mites from larger colonies or breeding operations is often futile, and control of the problem, rather than total eradication, is a more realistic goal. Página 278
In the gerbil and the hamster, Demodex spp. is usually secondary to some other condition, such as age (most common in hamsters over one and one-half years old), renal disease, malnutrition or any systemic condition. Mitaban (Amitraz, Upjohn, Kalamazoo, MI), a common miticide in small animal medicine, has been reported effective in the hamster at the recommended dose on the label, administered every two weeks for three to six treatments (Harkness and Wagner, 1989). Another reported therapy includes a mixture of Ronnel and Propylene glycol (1:5.5) used as a dip for five weeks (Toy, in Manual of Exotic Pets, 1985). In my experience, both of these suggested treatments have a high potential to kill the patient. If you chose to use them, consider diluting them two to four times more than the recommended dilutions. Regardless of the treatment selected, there are three important points that must be addressed: First, Demodicosis is usually secondary to a more serious problem. Treating the mites alone will not cure the underlying condition. Second, the mites will usually come back - ALWAYS warn your clients. Last, these miticides are toxic, and, these patients are not in the best of health. The dips can be dangerous to the patient if not used with extreme caution. There are a number of treatments suggested in the literature for the treatment of mites (other than Demodex spp.) and lice. Each has its advantage and disadvantage. Many factors need to be considered, including, the species being treated, the age of the affected individuals, the parasite being treated, the number of animals being treated, the intended use of the patients (pets, food animals [reptile/raptor prey] or breeders), cost and owner compliance. Individual animals may benefit from one or two injections, spaced seven to ten days apart, of ivermectin (IVOMEC, Merck, Sharpe and Dohme, Rahway, NJ). Dosages suggested range from 200-400 mcg/kg, IM or SC. Because of the ease of treatment, low cost and effectiveness, this is the author's first choice. The ivermectin comes as a cattle or swine preparation (1%, which is 10 mg/ml). This is too concentrated to be using with any accuracy in most of the tiny rodents that you will be treating. Accurate drug delivery can be accomplished with the use of either a microliter syringe, or by diluting the ivermectin in sterile propylene glycol. Do not dilute the ivermectin in saline or water, as either of these diluents will crystallize the ivermectin, rendering it ineffective. In addition to treating the mites/lice on the host it is imperative that a massive cleaning program be initiated in the host's cage/environment. Bedding, caging and cage furniture must be either sanitized or discarded. Wood, cardboard or any porous material is better discarded than treated. If the environment is not effectively sterilized of the mites/eggs/lice/nits, the problem will return. Página 279
Most of the mites and lice are species specific and pose no threat to humans. However, Cheyletiella spp. and Ornithonyssus bacoti have been reported to cause a pruritic dermatitis in people. In addition, the latter has been implicated as a vector of murine typhus, Q fever and plague. Specific Conditions Guinea Pigs Salmonellosis - Of all the small mammal pets, the guinea pig is perhaps the most sensitive to salmonella. Salmonella typhimurium or S. enteritidis are the two most common serotypes involved. Contamination is through the fecal oral route, with signs being multiple, including general unthriftiness, anorexia, weight loss, ocular discharge and acute death. The chronic infections are the most common. Treatment should be carefully considered since there is a high potential for zoonosis. Cervical Lymphadenitis - Often called "Lumps" by lay guinea pig owners, and is caused by Strep zooepidemicus. This is common, especially in multiple animal households or those animals from pet stores. This infection also has potential for becoming zoonotic. The bacteria enters through the conjuctiva or abrasions in the oral cavity from rough food or abnormal teeth. The typical presentation is swollen cervical lymph nodes, but, the infection can spread to a septicemia, pneumonia, torticollis and ultimately death. Diagnosis is made from physical examination findings, cytology and gram stain of the nodes. Treatment involves draining of the infected nodes and antibiotics such as trimethoprim/sulfa or chloramphenicol. Bordetellosis - Caused by Bordetella bronchiseptica, is a common disease in guinea pigs. Some guinea pigs can act as carriers of Bordetella, harboring it in their nasal cavities or middle ear. In addition, it is carried by rabbits and can easily spread to guinea pigs, where it causes anorexia, lethargy, nasal and ocular discharge, torticollis, pneumonia and death. Stress or malnutrition can precipitate the disease in the carrier animals. Diagnosis is by history and physical examination, as well as culture of nasal exudate or lung washings. Treatment with antibiotics may be of some benefit if caught early. Hypovitaminosis C - The guinea pig is unable to synthesize vitamin C, and therefore must have it in their diets. Stressful factors such as pregnancy and lactation can increase the requirements for vitamin C in the diet. Vitamin C is a water soluble vitamin, and signs of scurvy can develop in as little as two weeks. A common cause of deficiencies is the prolonged storage of food, since vitamin C is relatively labile, losing as much as 50% of its potency in just six weeks. Clinical signs reflect vitamin C's role in the maintenance of collagen and relate to Página 280
bone and vascular defects. Loosening of the teeth, hemorrhage, epiphyseal fractures and osteoporosis. Patients are reluctant to ambulate, appear painful when handled, are lethargic and anorectic. Diagnosis is based on thorough history, physical examinatin and radiographic changes to the long bones. Treatment includes administration of ascorbic acid at 10 mg/kg. vitamin C added to the water or feed can occasionally discourage feeding or drinking. Recovery is rapid, usually within two to three weeks. Supportive care must be provided, antibiotics if the animal is otherwise ill. Fresh, green leafy vegetables should always be provided as part of the animal's daily ration in order to prevent scurvy. Malocclusion - Unlike in the rabbit, where the incisors are the most likely teeth to over grow, in the guinea pig, it is the cheek teeth that tend to not wear properly, trapping the tongue under the lingual surface of the lower molars. Diagnosis is made by physical examination. Common findings include slobbers, anorexia, weight loss and possibly cervical lymphadenitis. Oral examination confirms the presence of the overgrown molars. Treatment involves trimming the lingual border of the teeth with a dental burr, a dremmel, or rongeurs. Take care not to shatter the teeth, as sharp edges may predispose to abscess formation. Rats Mammary Gland Fibroadenomas - By far the most common neoplasm that I see in rats is the mammary gland fibroadenoma. The mammary glands in the rat, both the male and the female, extend along the ventrum, cranially to the pectoral girdle, and extending up over each shoulder to the dorsum of the back. When affected, these tumors can equal the size of the rat. These tumors are well demarcated, and usually have a readily identifiable vascular supply, making surgical removal a rather simple task, even for the extremely large masses. Red Tears - Anything that causes stress in rats can result in chromodacryorrhea, or red tears. These tears are caused by porphyrins that enter the tear film. Sialodacryoadenitis virus (SDAV) is a common infection of pet rats. It is usually dormant except in cases of stress, when it becomes clinically apparent, resulting in the red tears. Clinical signs include the red tears, photophobia, blepharospasm and corneal ulcerations. The virus can cause necrosis of the lacrimal and salivary glands, and as a result, there may be swelling in the cervical region. There is no treatment for this condition except for stress management, and ophthalmics necessary to protect the affected eyes. The virus is usually self-limiting in approximately seven to 14 days. Incisor Malocclusions - This is a common problem. The cause is unknown, but may relate to lack of gnawing material, improper foods or a genetic predisposition. Affected animals may Página 281
have difficulty prehending food, become anorectic, lose weight and have a general unthrifty appearance. Treatment includes trimming the teeth back to a normal length. A diamond blade, dremmel or dental burr are recommended tools. Care should be taken not to crack the teeth as that can potentially cause tooth root infections. Mice Neoplasms - Mammary tumors (different than those seen in rats), lymphosarcomas and pulmonary neoplasms are the most common. However, unlike the mammary tumors seen in rats, the mammary tumors in mice are not readily resectable. Likewise, the other tumors seen in mice are not readily treatable. Murine pneumonias - Mice and rats are natural hosts for Mycoplasma pulmonis and M. arthritidis. These mycoplasmas cause pneumonias and genital infections. Rabbits, guinea pigs and other rodents may carry the organisms, but they are not clinically affected. Sendai virus is another pathogen that causes respiratory disease in mice. Mice can carry the virus where it causes a subclinical infection. Affected mice may develop bronchopneumonia and otitis, and can be found in conjunction with Pasteurella and Mycoplasma. There is no treatment for Sendai virus, and for all practical purposes, it is not possible to eliminate mycoplasma from the host. Hamsters Diarrhea - "Wet tail." Several factors cause diarrhea in hamsters. Campylobacteria is the most common bacteria responsible, and results in a condition called proliferative ileitis. The disease is most commonly seen in weanlings that are 3-8 weeks old. There is a 90% mortality. Treatment includes oral erythromycin or tetracycline in the drinking water, but, these drugs may make the condition worse as they tend to affect the animal's normal intestinal flora. The prognosis is considered poor to grave. Gerbils Epilepsy - Gerbils will display seizure like activity when excited or handled roughly. The seizures may last from 30 to 120 seconds. Gentle handling as juveniles may accustom the animals to handling as adults. Página 282
Neoplasia - Adult females have a 25% incidence of reproductive tract disease in animals over two years of age. Cutaneous neoplasms and skin gland tumors may also be seen. Página 283