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United States Department of Agriculture

Agricultural Research Service

Research Project: PROTOZOAN PARASITES AFFECTING FOOD ANIMALS, FOOD SAFETY, AND PUBLIC HEALTH Title: Epidemiology and diagnosis of Sarcocystis: zoonotic aspects

Author
item Fayer, Ronald

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 29, 2010
Publication Date: June 3, 2010
Citation: Fayer, R. 2010. Epidemiology and diagnosis of Sarcocystis: zoonotic aspects. [abstract]. Workshop for the National Reference Laboratories for Parasites of the Member States of European Union.

Technical Abstract: Sarcocystis species have long been recognized as either grossly visible or microscopic cysts in the muscles of humans and a wide variety of animals. They have been especially evident in meat animals such as cattle and sheep and have been the cause of extensive and expensive condemnations at the time of meat inspection. Once thought to be a variety of fungus, they are now known to be intracellular protozoan parasites with an intermediate-definitive host life cycle based on a prey- predator relationship. Asexual stages develop in intermediate hosts after they ingest the oocyst stage from definitive host feces and terminate with the formation of intramuscular cysts (sarcocysts). Mature sarcocysts contain numerous comma-shaped motile bodies called zoites. Sarcocysts in meat eaten by a definitive host release the zoites that invade cells lining the intestine and initiate sexual stages that terminate in oocysts excreted in the feces. Most Sarcocystis species infect specific hosts or closely related host species. For example, humans and some primates are definitive hosts for Sarcocystis hominis and S. suihominis after eating raw meat from cattle and pigs, respectively. The prevalence of intestinal sarcocystosis in humans is low, and rarely associated with illness except for volunteers who ingested large numbers of sarcocysts. Clinical signs such as vomition, dyspnea, weakness, and diarrhea were associated with eating the meat containing S. hominis and S. suihominis. Human (intermediate host) cases with intramuscular cysts number less than 100 and are of unknown origin. The asexual stages, including sarcocysts, can stimulate a strong inflammatory response. Livestock have suffered acute debilitating infections resulting in abortion and death or chronic infections with failure to grow or thrive. This review provides a summary of Sarcocystis biology, its morphology, life cycle, host specificity, prevalence, diagnosis, treatment, and prevention strategies, for human and food animal infections.

Last Modified: 7/24/2014
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