HISTORY AND PHYSICAL EXAMINATION
Reptiles are considered obligate closed-mouth breathers. A reptile that is open mouth breathing should be considered a medical emergency. Most reptiles with respiratory disease will elevate their head in an attempt to straighten their trachea. Aquatic chelonians with respiratory disease may have difficulty swimming and will frequently have difficulty diving. A thorough history is essential to identifying a potential etiology(ies)responsible for respiratory disease in reptiles. In many cases, there will be deficiencies in the animal’s husbandry. Historical questions should include the environmental temperature range, humidity, enclosure size, substrate, cage furniture, animal density, exposure to commercial products (toxins), diet, and water source .
The physical examination should be thorough and complete. The nares should be clear and free of discharge. The oral cavity should be examined closely. The glottis should be moist and free of discharge. It is difficult to auscult reptiles using a standard stethoscope, and some clinicians do not advocate ausculting reptiles. However, the author strongly recommends ausculting all reptile patients. A moist paper towel should be placed on the animal in the general vicinity of the lungs to reduce friction and noise associated with the bell housing of the stethoscope on the scales or scutes of a reptile.
BACTERIAL DISEASES
Bacterial diseases are the most common cause of respiratory disease in captive reptiles. The majority of the isolates recovered from reptiles with pneumonia are opportunistic Gram-negative bacteria. Many of these isolates are typically found as inhabitants of the indigenous oral microbial flora. Tracheal/lung washes may be performed to collect samples for microbiological culture. An antimicrobial sensitivity assay should be performed on the isolate to determine the most appropriate antibiotic. A fluroquinolone, potentiated sulfa, cephalosporin, or aminoglycoside many be used as a first order antibiotic while the sensitivity assay is pending.
PARASITES
Endoparasites are a common finding in wild caught reptiles. Digenetic trematodes are frequently found in the trachea or lungs. The eggs of these parasites are generally disseminated with the sputum or swallowed and shed in the feces. Because these parasites require an invertebrate intermediate host, trematode infestations are generally self-limiting. Praziquantel can be given at 5-7 mg/kg per os or intramuscularly once every 10 days for three treatments to eradicate trematodes. Nematodes, including Entomelas spp., Rhabdias spp., and Strongyloides spp. are commonly identified in wild caught reptiles. These parasites can reinfest a host through the oral or percutaneous route; therefore treatment should include both the reptile and its environment.Fenbendazole can be given at 25-50 mg/kg per os once a day for 3 days to eliminate these parasites. Pentastomids are primitive annulate metazoans that infest reptiles. These parasites are generally found in the lungs. Diagnosis can be made on fecal float, radiographs, and/or endoscopy. Ivermectin (0.2 mg/kg) has been used to eradicate this parasite, but success using ivermectin may be variable. Surgical removal of the parasites provides the best results.
FUNGAL DISEASES
Fungal diseases associated with the respiratory system are rare in the author’s practice. Most respiratory fungal disease is identified in immunocompromised reptile patients. Reptiles provided inadequate husbandry are generally more susceptible to fungal pathogens. Many of the fungal isolates recovered from respiratory lesions are ubiquitous, opportunistic organisms. Reptiles maintained on long-term antibiotic therapy may also be predisposed to fungal infections. Treatment should include the removal of granulomatous masses and the administration of systemic antifungal therapy (Itraconazole 5-10 mg/kg POq 24h).
VIRAL DISEASES
Paramyxovirus has been associated with high morbidity and mortality in snake populations. This virus primarily affects the respiratory system and central nervous system. Diagnosis is generally made using a hemagglutination inhibition assay or at post-mortem. There is no effective treatment for this virus. Inclusion body disease is another viral disease that is associated with high mortalities in snake populations. A retrovirus is considered to be the etiologic agent of IBD, but this has not been confirmed. Affected snakes frequently develop progressive central nervous system deficits and secondary pneumonia. Diagnosis is generally made at post-mortem, although ante-mortem diagnosis from biopsies of the esophagus, liver or kidney may also be done. Herpes virus has been associated with severe disease in chelonians. Affected animals may present with both upper and lower respiratory tract disease, diarrhea, and central nervous system deficits. Diagnosis can be made from biopsies of affected tissues (histopathology) or currently available molecular diagnostic assays. There is no effective treatment for this virus.