Submitted to: Journal of Comparative Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2006
Publication Date: 12/1/2006
Citation: Wouda, W., Snoep, J.J., Dubey, J.P. 2006. Eosinophilic myositis due to Sarcocystis hominis in a beef cow. Journal of Comparative Pathology. 135:249-253.
Interpretive Summary: Sarcocystis species are single celled parasites that cause illness in humans and livestock. Humans can become infected with this parasite by ingesting infected pork and beef. Cattle and pigs can become infected by ingesting food and water contaminated with the resistant parasite stages excreted in feces of infected humans. Scientists at the Beltsville Agricultural Research Center and and a diagnostic lab. in the Netherland report myostis in a beef cow infected with Sarcocystis hominis that cycles between humans and cattle. The cow is presumed to have become infected by grazing on pasture contaminated with human feces.The results will be of interest to biologists, parasitologists, public health workers,and veterinarians.
Technical Abstract: A case of eosinophilic myositis in an eight-year-old beef cow was investigated. The cow originated from a herd that had a high incidence of eosinophilic myositis in slaughtered adult females during a period of two years. Histologically, the lesions in the muscles were characterized as granulomas with a central core of degenerate eosinophils and remnants of necrotic muscle fibres, surrounded by a rim of epithelioid cells and fibrous tissue with an infiltrate predominantly of eosinophils radiating outward into the intermysium. Degenerate sarcocysts with a 7-9 µm thick radiated sarcocyst wall were present in the suppurative centre of most lesions examined. Intact sarcocysts with similar morphology were present in adjacent muscle fibres but without an associated inflammatory reaction. By transmission electron microscopy the sarcocysts were identified as Sarcocystis hominis, based on the morphology of the sarcocyst wall villar protrusions, which were broad-based, cylindrical, with a blunt distal end, and contained numerous long microfilaments. There was circumstantial evidence supporting the involvement of a human source of the infection, as human faecal material had been spread onto the pasture grazed by the cattle. In conclusion, evidence is provided for a causal relationship between an infection with S. hominis and eosinophilic myositis in cattle.