Submitted to: Journal of Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/30/2001
Publication Date: N/A
Citation: Interpretive Summary: Sarcocystis neurona is a single-celled parasite of livestock. It causes a fatal disease of horses, equine protozoal myeloencephalitis (EPM). Horses become infected by ingesting food or water contaminated with spores (sporocysts) of the parasite excreted in feces of opossums. The opossums become infected by ingesting the encysted stage (sarcocysts) of the parasite in cats and armadillos muscles. Scientists at the Beltsville Agricultural Research Center describe structure of the sarcocyst in the muscles of experimentally-infected cats. These results will be of interest to biologists, pathologists and parasitologists.
Technical Abstract: The ultrastructure of Sarcocystis neurona sarcocysts was studied from muscle of an experimentally-infected cat. The cat was killed 144 days after being fed sporocysts from a naturally- infected opossum. Sarcocysts were microscopic, up to 700 micrometers long and up to 50 micrometers wide. By light microscopy, the sarcocyst wall was 1-2 micrometers thick. Ultrastructurally, the sarcocyst wall consisted of numerous villar protrusions. The villar protrusions were up to 2.8 micrometers long and up to 0.4 micrometers wide, with a tapered end. Microtubules extended from the tip of the villus to the base and occasionally extended deep into the granular layer. The granular layer was 0.5 micrometers thick. Longitudinally-cut bradyzoites were 5.2 x 1.2 (4.8 to 6.5 x 1.0 to 1.3) micrometers in size. Micronemes in bradyzoites were numerous and located in the anterior-third of the conoidal end.