Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2015
Publication Date: 10/1/2015
Citation: Dubey, J.P. 2015. Foodborne and waterborne zoonotic sarcocystosis. Foodborne Pathogens and Disease. 1:2-11.
Interpretive Summary: Zoonosis caused by Toxoplasma, and related parasite Sarcocystis continues to be of public health concern. Sarcocystis is a single celled parasite. Two of the Sarcocystis species, S. hominis and S. suihominis are transmissible to humans by eating raw/undercooked beef or pork, respectively. After ingestion of infected beef or pork humans excrete an environmentally resistant stage (sporocyst) in feces and can suffer from digestive problems (nausea, diarrhea, vomiting). Livestock become infected by ingesting food and water contaminated with sporocysts. ARS scientists recently reported another new species of Sarcocystis, S. heydorni, in cattle experimentally infected with sporocysts from human feces. In the present paper an ARS scientist reviews current status of zoonotic sarcocystosis. These findings are of public and professional interest.
Technical Abstract: The ingestion of raw beef or pork infected with Sarcocystis can cause illness in humans. Allergic/toxic type symptoms (nausea, vomiting) can occur within three days of consuming infected meat; these symptoms are considered due to toxic substances in sarcocysts or to other factors in raw meat. Diarrhea and abdominal pain are associated with excretion of sporulated sporocysts in human feces usually within 8-14 days after ingestion of infected meat. The intestinal phase is often self-limiting but sporocysts may be excreted for months. There appears to be little or no immunity to excretion of sporocysts after ingesting each infected meal. The clinical illness is more severe after eating infected pork versus infected beef. There is one zoonotic Sarcocystis species in pork, S. suihominis, with domestic and wild pigs as intermediate hosts. Two zoonotic species are present in cattle, S. hominis, and S. rommeli; neither has been recognized in North America. Although isolated cases of muscular sarcocysts have been known for more than 100 years, recently a mysterious serious, diagnostically challenging illness has been reported in humans on vacation/travel to Malaysia; sarcocysts were detected histologically in biopsy of muscles from some of these patients. These outbreaks of sarcocystosis-like illness in humans are summarized. Molecular epidemiological evidence suggests a new type of zoonosis linked to ingestion of food and water contaminated with a S. nesbitti-like parasite. Sarcocystis nesbitti life cycle is unknown. Maccaque monkeys are thought to be its intermediate hosts and unknown snakes as definitive hosts. Evidence linking S. nesbitti to human outbreaks or lack of it is reviewed.