Description of Sarcocystis rauschorum sp.n. (Protozoa: Sarcocystidae) with experimental cyclic transmission between varying lemmings (Dicrostonyx richardsoni) and snowy owls (Nyctea scandiaca)

Free sporocysts of a Sarcocystis-like organism (11.6 x 9.2 micro m with a diffuse residuum of numerous small refractile granules) from intestinal scrapings of an N. scandiaca from Saskatchewan, Canada, were orally administered to laboratory-reared D. richardsoni. Merants were present in hepatocytes after 7 days. Cysts of the parasite (named S. rauschorum n.sp.) developed in striated muscle and contained metrocytes (4.6 x 3.8 micro m) 14 days after infection; bradyzoites (6 x 2 micro m) were present as early as day 28. Cysts obtained on day 84 were not macroscopic (greatest diameter 80.9 micro m, least 70.9 micro m) with walls 0.35-0.70 micro m thick. Rats, mice, Peromyscus leucopus, Clethrionomys gapperi and Lemmus sibiricus were not suitable intermediate hosts. Carcasses of D. richardsoni containing cysts (57 and 84 days after infection) were fed to 3 Sarcocystis-free N. scandiaca. The prepatent period was 7 days and patency lasted 12-19 days. Sporogony occurred in the lamina propria throughout the length of the small intestine. Free sporocysts (10.4 x 8.2 micro m with a compact residuum of numerous refractile granules) from experimentally infected N. scandiaca were infective to D. richardsoni..