Respiratory diseases of small mammals (Proceedings)
Respiratory diseases in small mammals can be challenging. Although anatomy is similar, there are variations in anatomy that can predispose to certain diseases, or can interfere with interpretation of test results. The diseases these small patients acquire can vary greatly, and it can be extremely difficult to obtain samples for diagnostic evaluation, so it is important for the practitioner to be familiar with the common respiratory diseases in order to appropriately diagnose and treat these animals.
Ferret Respiratory Diseases
Among the small exotic species commonly kept as pets, ferrets are the most similar to dogs and cats. The thoracic cavity in ferrets is elongated, with the heart located between the 6th and 8th ribs, and the heart will be ausculted much more caudally than expected. Sinus arrhythmia is variation of normal in ferrets. The lungs are generous with respect to total body size. Radiographically, the ventral margin of the heart may be in contact with the sternum on a lateral view. Ferrets with respiratory disease or cardiac disease often exhibit general, non-specific signs such as lethargy, weakness, and hind limb paresis.There are a wide variety of diseases that cause respiratory signs in ferrets. When in doubt with a ferret, remember the principles of traditional companion animal medicine. Ferrets can easily be intubated, usually with a 2.5 or 3.0 mm endotracheal tube. If there is pleural effusion, perform thoracocentesis. If there is cardiomegaly, pursue heart disease; if pulmonary consolidation is present, this supports pneumonia. Tracheal lavage, or even lung aspirates can be performed as in more traditional companion animal species. Diagnostics for the ferret are safe and readily available, and should not be overlooked.
Ferrets are susceptible to Orthomyxoviridae, the human influenza viruses. This can be transmitted from ferret to human, ferret to ferret, or most commonly via human to ferret contact. Veterinarians and staff with cold or flu symptoms should wear a mask and wash hands prior to handling any ferret. Clinical signs, similar to humans, include lethargy, fever, sneezing, mucoid ocular and/or nasal discharge, and inappetence or anorexia. Fever, if present, typically lasts 48-72 hours. Although extremely uncommon, pneumonia is a sequela if secondary bacterial infection occurs. Diagnosis is based on clinical signs, history of exposure, and in many cases, duration of disease (see canine distemper virus, below). Virus isolation and ELISA for antibody are available but not commonly used. Leukopenia is an inconsistent finding. Treatment is limited to supportive care, usually fluid therapy and nutritional support (force feeding) if anorexia is severe. Human anti-influenza medications can be used. Antibiotics are only indicated if secondary bacterial infection is suspected or is imminent due to leukopenia. Pediatric cough suppressants or diphenhydramine can be used if necessary. Most ferrets with influenza do not require hospitalization. Clinical signs generally resolve within 5-7 days.
Canine Distemper Virus
Although rare, this is extremely important to recognize in ferrets, as the disease is nearly 100% fatal. Transmission is from infected dogs, other ferrets, or infected raccoons, but humans may serve as a mechanical vector. Clinical signs develop within 7-10 days of exposure, and may be similar initially to those of influenza virus. Ferrets may be presented with lethargy, fever, inappetence or anorexia, sneezing, mucopurulent ocular and nasal discharge, photophobia, porphyrin staining or dermatitis of the face and eyes, and hyperkeratosis of the footpads. The dermatitis and/or porphyrin staining of the face is pathognomonic for distemper in ferrets (looks like food allergy in a cat). Diagnosis is made by history (questionable vaccination history), potential exposure, clinical signs, and either fluorescent antibody staining or identification of the antigen in cells obtained for biopsy. There is no treatment; euthanasia is recommended. Keep separate from other ferrets and dogs.
Pneumonia in ferrets is rare. Aspiration pneumonia may occur and will have a distribution similar to other companion animals. Diagnosis is based on radiography. Tracheal lavage is performed as in other species (3mm endotracheal tube will be appropriate for most ferrets). Treat with appropriate antimicrobials based on culture & sensitivity, supportive care, and perhaps nebulization and coupage. Evaluate radiographs carefully for megaesophagus if pneumonia is suspected.