Sheep Experimentally Infected with Sarcocystis from Dogs. I. Disease in Young Lambs

Abstract

Polled Dorset lambs (8) were orally inoculated with Sarcocystis ovicanis sporocysts. Two lambs that received 100,000 or 200,000 sporocysts became clinically ill, recovered and were killed 67 and 88 days after inoculation (DAI). Numerous intramuscular cysts were found in their skeletal and cardiac muscles. Three lambs received 100,000 sporocysts, 3 lambs received 1 million sporocysts and 3 lambs received no sporocysts. After an acute clinical illness characterized by anemia, inappetence, weight loss, fever and reduced serum protein, all lambs that received 100,000 sporocysts died 27-29 DAI; all that received 1 million sporocysts died 24-25 DAI. Hemorrhage involving striated muscle and visceral organs was the most apparent gross lesion. The heart appeared most severely affected. Schizonts were found in vascular endothelial cells of all 6 inoculated lambs. Uninoculated lambs remained healthy, and neither lesions nor parasites were found in any tissues. Dogs fed tissues containing S. ovicanis cysts produced sporocysts 11-37 days after feeding; cats fed similar stages produced no sporocysts. Dogs fed tissues containing schizonts produced no sporocysts.