ASK THE VET (Candidiasis)

In a previous column I wrote about Aspergillosis, a fungal infection that may affect young and stressed birds. In this column, I am writing about candidiasis, another fungal infection of birds.

Candidiasis is caused by the opportunistic yeast Candida albicans. It is commonly found in the environment and may be present in small numbers in a normal bird's digestive tract. It may, however, cause illness under certain conditions. Very young birds, especially those on antibiotics, may develop primary candidiasis due to their immature immune systems. Adult birds on long term antibiotics or suffering from malnutrition or other illnesses may develop secondary candidiasis. Antibiotics change the normal digestive tract flora and allow the organism to overgrow. Birds affected with beak lesions as a result of Beak and Feather virus often develop secondary candidiasis due to a poor immune system.

Candida albicans most often affects the crop, although the proventriculus (muscular stomach) and nontriculus (glandular stomach) may be affected as well. Candidiasis has also been found to affect the skin, respiratory tract, central nervous system and all other organs.

The severity of a candida infection often depends on the age of the bird and the state of its immune system. A very young or very ill bird may initially have a localized candida infection that spreads systemically to the blood, bone marrow, and other organs. Severe stress or immunosuppression can enable a localized infection to become an overwhelming systemic infection.

Regurgitation, anorexia, and delayed crop emptying may be present with a candida infection of the crop. Some birds develop a swollen, mucus-filled crop. White plaques may be present in the mouth if oral candida is present. These must be differentiated from Vitamin A deficiency, pox, and trichomoniasis (parasite).

Candidiasis may be suspected as a result of the history and clinical signs. Material from the site of infection may be stained with Gram's stain to identify the yeast. Just finding the yeast present is not conclusive of infection. The organism must be budding and causing histologic changes. Culturing is helpful to determine the most effective antifungal to use. Treatment of candida involves correcting predisposing factors, such as poor nutrition and any underlying illness as well as antifungal medication. Nystatin is an antifungal often used to treat upper gastrointestinal candidiasis since it is well accepted by the bird and is not toxic. Other antifungals are available for resistant strains of Candida albicans. Whenever birds, especially neonates, are placed on oral antibiotics, it is often recommended to give nystatin in conjunction with the antibiotic to try to prevent candidiasis.