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


DVM360 MAGAZINE


Control and treatment of aspergillosis can be difficult as well as expensive. Treatment often consists of antifungal therapy and supportive care. Antifungal medications that have been used in avian species include itraconazole, clotrimazole, terbinafine, enilconazole and amphotericin B. The latter of which is the only fungicidal drug available. Treatment and ultimately response to therapy may differ depending upon the severity and location of the infection. Therapy is usually long-term with patient response and serological testing used to monitor progress and response to therapy. The prognosis is usually considered poor. Most commonly, itraconazole (Sporonox)(Janssen Pharmaceutical, NV, Beerse, Belgium) is administered at a dose of 5-10 mg/kg orally once daily for most avian species. Extreme caution should be used if treating African grey parrots (Psittacus erithacus) with itraconazole. While some avian practitioners avoid the use of itraconazole in African grey parrots, others use a reduced dosage of 2.5-5.0 mg/kg given orally once daily. These patients should be monitored closely for anorexia and depression, which is indicative of possible toxicity related to itraconazole administration. Amphotericin B (X-Gen Pharmaceuticals Inc., Northport, N.Y.) is also commonly used in conjunction with other drugs to treat aspergillosis infections in avian patients and is administered intravenously (1.5 mg/kg IV every 8hrs for 3-7 days), intratracheally (1 mg/kg IT diluted to 1cc volume in sterile water every 12 hrs for 5 days), by intraosseous catheter (1.5 mg/kg every 6 hrs for 5 days or applied directly to granulomatous lesion in the coelomic cavity. Terbinafine hydrochloride (Novartis Pharmaceuticals) has also been used to treat fungal infections in avian species at a dose of 10-15 mg/kg given orally every 12-24 hours. However, it is considered to have poor intrinsic activity against some common yeasts and molds, which suggests that combination with an azole (fluconazole or itraconazole) or amphotericin B may be required if monotherapy does not result in clinical cure of the patient. For fungal infections involving privileged sites such as the eye or brain fluconazole (Pfizer Inc.) may be considered the drug of choice. However, it is also important to note that hydroxyitraconazole, the active metabolite of itraconazole is also able to penetrate into the CNS and may also be somewhat effective in treating fungal granulomatous lesions if present in the brain. Unfortunately, there is no vaccine currently available for the management of aspergillosis.


Photo 2: Budding Candida albicans in feces.
Candidiasis Candida albicans is another opportunistic yeast commonly found in the environment and may be a normal inhabitant of the gastrointestinal tract of avian species. Diseases are often seen in juvenile avian species following disruption of normal gastrointestinal flora following prolonged antibiotic administration, especially tetracyclines or concurrent illness.

Candidiasis is also known as "thrush" and occurs when superficial colonization of the gastrointestinal mucosa progresses to deep-tissue invasion. The result is uninhibited growth and colonization of the gastrointestinal tract by the organism. If unchecked, Candida sp may become systemic allowing for dissemination to occur.

Clinical signs of candidiasis vary depending upon the location of infection. Local infections within the oropharynx may cause difficulty or reluctance to swallow food and halitosis. Oropharyngeal infections commonly results in psuedomembranes/plaques of necrotic debris overlying the mucous membranes or catarrhal inflammation giving the mucous membranes a "Turkish towel" appearance. Infection within the crop may result in regurgitation, vomiting, delayed crop emptying, anorexia, palpable thickening of the crop and ingluviolith formation. Proventricular and ventricular infections may cause vomiting, weight loss, diarrhea and general malaise. Candida sp may also colonize the respiratory tract leading to dyspnea, ocular or nasal discharge and sneezing. Less commonly, Candida sp may also infect ocular tissues, skin, bone marrow, liver, pericardial tissues and the CNS (canaries). Candida parasilosis has been reported to cause systemic infection of the bone marrow and liver as well as splenic degeneration.

Diagnosis of candidiasis is usually based upon the presence of budding Candida sp. (3-6 micrometers in diameter) with Grams', Diff-Quik, new methylene blue or lactophenol cotton blue stains of the crop contents, feces, or regurgitated/vomited material or lesion(s). Skin scrapings and celophane tape tests may also be performed to aid in the diagnosis of suspected yeast infections of the skin.


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