Premature parturition in ewes inoculated with Sarcocystis ovicanis.

A dose of 6 X 10(4) Sarcocystis ovicanis sporocysts produced premature parturition in ewes and eventually proved fatal. The main pathological findings were myositis, myocarditis and encephalitis. Dose rates over the range of 2.5 X 10(3) to 6 X 10(4) depressed the haematocrit levels of pregnant ewes during the period 5-9 weeks after inoculation. Previous infection with S. gigantia did not protect from subsequent challenge with S. ovicanis.