Sarcocystis encephalitis in a cockatiel.

: A sporozoan organism was considered to be the causative agent of central nervous system disease in a cockatiel. The ultrastructural characteristics were typical of the coccidian group Apicomplexa, and the fact that organisms were free within the cytoplasm of infected cells and not within a vacuole, indicated they were Sarcocystis. Light and electron microscopic evaluation of brain tissue demonstrated protozoal organisms associated with areas of necrosis. Differential diagnosis of central nervous system disease in pet birds should include protozoal encephalitis.