Fungal diseases of pet birds: Recognize infection early - DVM
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Fungal diseases of pet birds: Recognize infection early


DVM360 MAGAZINE



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Resolving predisposing factors Treatment consists of identifying and resolving predisposing factors if any, and antimicrobial therapy with nystatin, fluconazole, itraconazole or amphotericin B. Candida sp might develop resistance to some antifungal medications. For example, Fluoropyrimidines such as flucytosine may not be the best choice for treating Candida sp infections. Klepser ME suggests that 10 percent of all C. albicans are intrinsically resistant to flucytosine and another 30 percent exposed to the drug may develop resistance, at least in humans. Most commonly nystatin (Alpharma USPD Inc., Baltimore) is administered (100,000 IU/kg orally twice daily). For severe infections involving tissue invasion or resistant infections, fluconazole given at 20 mg/kg orally every 48 hours for two to three treatments might be effective. Environmental factors such as poor sanitation must be addressed to improve clinical outcome of disease in young birds.

Cryptococcosis Disease caused by the saprophytic fungus Cryptococcus neoformans, which may be found in soil contaminated with pigeon feces, is uncommon yet an important fungal disease of avian species. Cryptococcosis has been reported in several avian species including small passerines and companion psittacines, and some avian species such as feral pigeons may serve as carriers for the organism. Avian and exotic pet practitioners should also be aware of its zoonotic potential. Nosanchuk JD et al described the possible transmission of C. neoformans from a cockatoo to a 72-year-old woman who was receiving immunosuppressive medications following renal transplantation. C. neoformans isolates strongly suggest that the patient's infection resulted from exposure to aerosolized cockatoo excreta.

Clinical signs of Cryptococcus infections may be non-specific and include weakness, lethargy, depression, anorexia, diarrhea, dyspnea, weight loss, blindness and paralysis. Neurologic signs may occur with CNS (brain and meningeal) involvement. Moderate to severe dyspnea may be seen with involvement of both the upper or lower respiratory tract.

Ante-mortem diagnosis of Cryptococcosis is difficult. A definitive diagnosis of Cryptococcosis requires demonstration of the oval to round yeast with a mucopolysaccharide capsule on cytologic or histologic examination of tracheal washes or exudates and by isolation and culture. A gelatinous, mucoid exudate may be noted within the long bones, respiratory tract, coelomic cavity, sinuses and brain at necropsy. CNS signs in any avian species with gelatinous mucoid exudates is considered highly suspicious for Cryptococcosis.

Avian veterinarians should use extreme caution when handling patients suspected of having Cryptococcosis. Zoonotic infections may occur through inhaling dust from dried droppings of pigeons, starlings and other species. In avian patients, Amphotericin B, itraconazole and ketoconazole have been recommended as possible treatment options; however, fluconazole may be a better choice for infections of the CNS. Prognosis for successful treatment is extremely poor.

Rhodotoruliasis Rhodotorula mucilaginosa is a yeast that infects the skin and is occasionally seen in raptors (especially falcons). The organisms typically cause greasy, yellowish-brown crust overlying cracked and discolored areas of skin in the axillary area of the wings or between the thigh musculature and the body wall. Without treatment, lesions may become hyperkeratotic resulting in proliferative, horny growths on the effected skin.

Diagnosis of infection is based on physical examination, cytology, culture or histopathology of infected tissues. Treatment requires removal of horny growths if present and several weeks of therapy with a topical antifungal cream. Topical or systemic antibiotics should be considered to prevent secondary bacterial infections from developing. Additionally, movement of the infected area should also be restricted to allow the wounds to heal.

Mucormycosis (Mucor spp, Absidia spp and Rhizopus spp) The saprophytic fungi that make up this group of organisms causes disease of varying forms depending upon the organ system effected. Clinical signs of disease may be the result of enteritis, air sacculitis, osteomyelitis, myocarditis and nephritis. Mycotic infections due to Mucor sp have been reported in African grey parrots. Ante-mortem diagnosis is uncommon and no effective treatment has been reported.


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