Ultrastructure of tachyzoites, bradyzoites and tissue cysts of Neospora caninum.
Dividing tachyzoites of Neospora caninum were 4 x 3 microns and had ultrastructural characteristics typical for the cyst-forming coccidia. Unusual ultrastructural characteristics of fully-formed tachyzoites included no micropores, 8-12 anterior and 4-6 posterior rhoptries, and a few posterior micronemes. Most tachyzoites were located free in the host cell cytoplasm; only a few occurred within a parasitophorous vacuole. Parasite multiplication appeared to be rapid because most organisms were in various stages of endodyogeny. Neural tissue cysts of N. caninum were 24.3 x 19.2 microns and contained 50-200 bradyzoites (7.3 x 1.5 microns), which lacked micropores. The cyst wall was 0.74-1.12 microns thick and consisted of the primary cyst wall (the parasitophorous vacuole membrane) and a thick granular layer with electron-dense vesicles.
Speer
C A
CA
Veterinary Research Laboratory, Montana State University, Bozeman 59717.
Dubey
J P
JP
D000818:Animals; D002371:Cat Diseases / Q000469:parasitology*; D002415:Cats; D003044:Coccidia / Q000648:ultrastructure*; D003048:Coccidiosis / Q000469:parasitology / Q000662:veterinary*; D004283:Dog Diseases / Q000469:parasitology*; D004285:Dogs; D008854:Microscopy, Electron; D012867:Skin / Q000469:parasitology / Q000648:ultrastructure