Candidiasis - The Merck Veterinary Manual

Candidiasis

Candida albicans is an opportunistic yeast and is not generally considered a primary pathogen. Small numbers of Candida are commonly found in the digestive tract of birds and may become pathologic when normal digestive flora are disrupted by immunosuppression. (See also candidiasis, Candidiasis: Introduction.)

Candidiasis most commonly affects unweaned chicks. Infection may be totally endogenous, with overgrowth due to the above-mentioned factors. It may also be caused or exacerbated by oral inoculation of large numbers of Candida , either by parental feeding or by hand feeding with utensils that are inadequately cleaned.

Clinical Findings:

Delayed crop emptying with a thickened crop is the most common finding in hand-fed birds. Regurgitation, weight loss, and depression may follow. See Table: Differential Diagnoses for Regurgitation in Pet Birds for differential diagnoses for regurgitation in birds. Adult birds may harbor low-grade candidiasis with few overt clinical signs.

Thrush, quail

Diagnosis:

Diagnosis is usually based on cytology. In more severe cases, when tissue invasion has occurred, the budding yeast will produce hyphae that can be seen in scrapings obtained from the crop or pharynx, or from the feces.

Treatment:

If a reservoir of exogenous Candida is present (eg, poor nest box or feeding tube hygiene), then eliminating the source of the Candida is critical. In neonates, the crop must often be emptied and smaller amounts fed until crop stasis has been resolved. Metoclopramide may aid in crop motility and preventing regurgitation. Nystatin (300,000 U/kg) is the most commonly used medication for candidiasis. Because it is fungistatic and is only effective when it directly contacts infected tissue, it is often administered tid, prior to feeding. Some Candida infections are resistant to nystatin, and in some birds immunosuppression precludes clearing of the infection by use of only a fungistatic agent. In these cases, systemic medications such as fluconazole (10 mg/kg, bid) are often used.

Flock treatment has historically been accomplished with the use of chlorhexidine at 10 mL/gal. of drinking water for 1-3 wk. Because chlorhexidine is a disinfectant, its use will also deplete the normal digestive flora. Acidification of the upper GI tract by use of apple cider vinegar has also been reported to resolve Candida overgrowth.

See Table: Antifungals Used in Caged Birds for some antifungals used in caged birds.