Diseases and conditions

Candida albicans / sour crop

One of the most common fungal species to cause problems in birds is Candida albicans.

Candida is a yeast, this is an organism that consists of a single cell and multiplies by dividing itself. If the conditions are right, Candida can multiply at an explosive rate. Candida is quite common in the digestive tract of healthy birds. It forms part of the natural flora. Sometimes however, the balance in the intestines can be disrupted, for instance if the normal intestinal bacteria are killed during treatment with antibiotics. This enables Candida to multiply without restraint and cause disease. In young birds, yeasts will be more easily pose a threat because of the immaturity of their immune system.

The severity of sickness depends on the overall health of the bird. Most problems with Candida occur in the digestive tract.


One of the most well-known diseases caused by Candida is candidiasis in the crop (‘sour crop’). It is most commonly seen in young birds. The crop is usually the only part of the digestive tract affected, although infection can also occur extend to the glandular stomach and gizzard.

If infected with Candida, the cells of the mucous membrane in the crop die off. White plaques of dead mucosa then appear. Also, a whitish to clear mucous forms in the crop.


Candisiasis causes regurgitation, delayed crop emptying, lethargy, loss of appetite and sometimes a completely blocked crop in young birds. Adult birds can have a swollen, mucous-filled crop. The plaques of the inner lining can complicate the crop emptying.


Besides problems in the crop, Candida can also affect the inside of the mouth. White plaques can also form here, covered in mucous.


Candida can also cause infections of the trachea in parrots and related species. Particularly after long spells of antibiotics use (for instance used to treat a bacterial infection of the respiratory tract), Candida can emerge in the absence of competition.


Infections in young birds with Candida are often the result of poor hygiene when preparing the birds' formula. Formula that has been standing in the open for some time can contain large numbers of yeasts. Fruit that has been out for a long time can also infect birds.



The symptoms and background history are usually enough to suspect Candida. Material taken from a crop swab can be microscopically examined. The yeast can then be identified after staining. Because they can normally be found in small numbers, finding low numbers of yeasts does not offer 100% proof that the Candida is the main cause of illness. Clinical candidiasis in the crop often reveals large amounts of yeasts that are seen to be budding.



An anti-yeast agent is an effective treatment method. Besides combating the yeast infection, it is also important to look for the reason of the infection. The yeast usually only has the opportunity to cause illness after the bird is weaker because of other factors, such as an infection or poor nutrition.