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Candidiasis in Poultry

(Thrush, Crop Mycosis, Sour Crop)


Jenny Nicholds

, DVM, DACPV, Poultry Diagnostic and Research Center, Department of Population Health, College of Veterinary Medicine, University of Georgia

Reviewed/Revised Apr 2023
Topic Resources

Candida spp are part of the normal microflora of the GI tract of many species, including birds. Candidiasis is an opportunistic infection that occurs when the normal microflora has been disrupted. Clinical signs include thickened mucosa and whitish, raised pseudomembranes. Presumptive diagnosis may be based on gross lesions. Antifungals may be effective in treatment.

Candidiasis is an opportunistic mycotic disease of the digestive tract of various avian species, including chickens, turkeys, and quail, due to Candida spp (primarily Candida albicans).

Etiology and Epidemiology of Candidiasis in Poultry

Candida spp are typically part of the commensal GI mycobiota of healthy poultry. Candidiasis results from disturbances of the normal microflora.

Candidiasis commonly develops after administration of therapeutic amounts of various antimicrobials or as a result of unsanitary drinking facilities. Heavy parasitism and malnutrition (vitamin A deficiency) have also been implicated. Young chicks and poults are the most susceptible.

Clinical Findings of Candidiasis in Poultry

Candidiasis in Poultry

Listlessness and inappetence may be the only clinical signs. Candidiasis lesions are most frequently found in the crop and consist of thickened mucosa and whitish, raised pseudomembranes. The same lesions may occur in the mouth and esophagus. Occasionally, shallow ulcers and sloughing of necrotic epithelium may be present.

Diagnosis of Candidiasis in Poultry

Diagnosis of candidiasis can be confirmed by histologic demonstration of tissue invasion. Microscopic lesions are characterized by epithelial hyperplasia, ballooning degeneration, and visualization of pseudohyphae and blastospores consistent with Candida spp.

Culture alone is not sufficient for diagnosis, because Candida spp are commensal organisms and can be commonly isolated from clinically normal birds.

Treatment, Control, and Prevention of Candidiasis in Poultry

No approved products are available for the treatment of candidiasis in the US. The antifungal medication nystatin, added to feed (100 g/ton of feed [110 mg/kg of feed] to be fed once daily for 7–10 days) or to drinking water (62.5–250 mg/L with sodium lauryl sulfate, a surfactant, at 7.8–25 mg/L for 5 days), may be effective in the treatment of turkeys with candidiasis. However, lack of an approved product for this application in some countries may render nystatin a nonviable option.

The occurrence of candidiasis can be decreased by the removal of contributing factors (eg, by improvements in sanitation and or by judicious antimicrobial use in poultry).

Key Points

  • Candidiasis is an opportunistic disease that results when the normal microflora has been disrupted, such as after antimicrobial administration.

  • Presumptive diagnosis may be based on gross lesions (thickened mucosa and whitish, raised pseudomembranes).

  • Nystatin has been used to treat candidiasis in poultry but constitutes extralabel drug use.

For More Information

  • Arne P, Lee MD. Fungal infections. In: Swayne DE, ed. Diseases of Poultry. 14th ed. Wiley-Blackwell; 2020:1124-1126.

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