Sarcocystosis: a clinical outbreak in dairy calves.

Death and illness in a pen of eight yearling dairy heifers was caused by the protozoan parasite Sarcocystis. All animals had weight loss, weakness, marginal anemia, and elevated serum enzymes. Affected animals had high hemagglutinating antibody titers to Sarcocystis antigen. Affected tissues of the two animals that died demonstrated schizonits and young cysts during pathologic examination. The resident farm dog was shedding Sarcocystis sporocysts and was incriminated as the source of infection.