SARCOCYSTIS-ASSOCIATED ENCEPHALITIS IN CHICKENS

Sarcocystis-associated encephalitis was diagnosed in a backyard chicke n nock that had nervous manifestations. The main histopathologic lesio n was necrotizing encephalitis characterized by a large focal area of necrosis infiltrated and surrounded by mononuclear cells, heterophils, and multinucleated giant cells. Schizonts and merozoites were observe d in the lesion. Immunohistochemical staining of the brain lesion reve aled positive reaction to Sarcocystis antiserum. The ultrastructural c haracteristics of the parasite were typical of Sarcocystis, including the presence of a nucleus, a conoid, numerous micronemes, and lack of rhoptries. Medication with amprolium and sulfamethazine or with chlort etracycline was not effective in controlling the mortality. Trapping o f opossums on the farm and relocating the chickens to clean, new premi ses seemed to reduce mortality from this infection.