Candidiasis is a fungal disease that usually occurs secondary in susceptible ducks. It is primarily caused by Candida albicans
, a yeast-like, opportunistic pathogen that is a normal inhabitant of the crop in healthy birds. Ducks with beak abnormalities, impacted food, tongue injuries, immunocompromised, receiving prolonged antibiotic therapy, heavy parasite loads, highly stressed, or affected by a primary illness are particularly vulnerable to developing candidiasis.
Characteristic of candidiasis is the presence of white to cream, cheesy patches or plaques (oral lesions) found in the duck's tongue, mouth, crop and esophagus tissue. Often, lesions may appear as necrotic patches that can be easily peeled back from the eroded mucosal surface. When the crop is involved, Candida
cause white curd-like plaques and reddening of the surrounding tissue. Affected ducks may appear listless, dehydrated, little to no appetite, loss of condition and 'yeasty or sour-like' breath. Some ducks may also show signs of mild conjunctivitis
Ducks with candidiasis can sometimes be concurrently infected with other diseases, which can complicate or confuse clinical signs observed. A case of concurrent infection in a backyard flock of chickens occurred in 2016 where the birds were concurrently infected with fowlpox and candidiasis.