title: Morphology of Sarcocystis gigantea in experimentally-infected sheep.
abstract: The development of the parasite and lesions was studied in 32 sheep killed 10 days to 47 months after inoculation with Sarcocystis gigantea sporocysts from cats. At 21-42 days post-inoculation (d.p.i.), there was a mild encephalitis, but organisms were not seen in the brain. Immature sarcocysts were detected from 40-84 d.p.i. The cyst wall was not measurable by light microscopy at 40 d.p.i., but was 1.5-2 microns thick at 84 d.p.i. At 119 d.p.i. both immature cysts containing only metrocytes, and mature cysts containing both metrocytes and merozoites, were present. These mature cysts did not have a secondary cyst wall. A mature cyst, 350 microns in length, was found in a sheep killed at 8 1/2 months p.i. At 10 m.p.i. cysts were up to 0.5 mm long and a secondary cyst wall was present. At 47 m.p.i. cysts were 2-5 X 4.5-7.5 mm, and were found only in the muscles of tongue, oesophagus, pharynx and flank.
mesh_terms: D000818:Animals; D004947:Esophagus / Q000469:parasitology; D008854:Microscopy, Electron; D009928:Organ Specificity; D012522:Sarcocystis / Q000254:growth & development / Q000648:ultrastructure*; D012523:Sarcocystosis / Q000469:parasitology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000469:parasitology*