Bovine sarcocystosis: Sarcocystis species, diagnosis, prevalence, economic and public health considerations, and association of Sarcocystis species with eosinophilic myositis in cattle

Authors: Dubey, Jitender; Rosenthal, Benjamin

Submitted to: International Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2022
Publication Date: 12/1/2022
Citation: Dubey, J.P., Rosenthal, B.M. 2022. Bovine sarcocystosis: Sarcocystis species, diagnosis, prevalence, economic and public health considerations, and association of Sarcocystis species with eosinophilic myositis in cattle. International Journal of Parasitology. 53(9):463-475. https://doi.org/10.1016/j.ijpara.2022.09.009.
DOI: https://doi.org/10.1016/j.ijpara.2022.09.009

Interpretive Summary: Sarcocystis species are a group of single celled parasites affecting humans and livestock. There are more than 200 species in the genus Sarcocystis. Some of them cause abortion, generalized disease, muscle weakness, low milk production, and retarded growth in livestock. Of the 7 named species of Sarcocystis in cattle, Sarcocystis cruzi is most pathogenic and the APDL scientists pioneered research on this species. Two species of Sarcocystis in beef are zoonotic, S. hominis and S.heydorni; humans become infected by eating undercooked beef infected with these parasites. Some species of Sarcocystis (Sarcocystis hirsuta) form cysts in beef that become grossly visible, and their presence can lead to condemnation of parts or whole carcasses mainly for aesthetic reasons. There is considerable confusion concerning the identity of Sarcocystis species in cattle, partly because most species (except S. cruzi) are poorly defined. Here the authors summarize status of Sarcocystis species in cattle and review information on a condition, bovine eosinophilic myocytis and its causal link to Sarcocystis. Economic and public health aspects of bovine sarcocystosis are discussed. This invited paper will be of interest to biologists, parasitologists, and veterinarians.

Technical Abstract: Infections by Sarcocystis in cattle are ubiqutous, world-wide. There is considerable confusion concerning the identity of Sarcocystis species in cattle. Proper diagnosis of Sarcocystis species is important to assess their economic and public health importance. Currently there are seven named species: Sarcocystis hirsuta, S. cuzi, S. hominis, S. bovifelis, S. heydorni, S. bovini and S. rommeli. Additionally, there are unnamed Sarcocystis species. Two species, S. hominis and S. heydorni (transmitted vis humans) are zoonotic. One species (S. hirsuta, contracted from cats) forms macroscopic cysts visible during carcass inspection. Current molecular characterization is based on DNA extracted from sarcocysts from naturally infected cattle because DNA was not characterized from tissues of experimentally infected cattle or feces of experimentally infected definitive hosts. Sarcocystis cruzi (transmitted via canids) is the most pathogenic species and it causes abortion, low milk yield, poor growth, and outbreaks of fatal sarcocystosis. Additionally, Sarcocystis infections have been linked to an inflammatory condition of striated muscles termed bovine eosinophilic myositis (BEM). Cattle affected by BEM appear clinically normal. Diagnosis of BEM at slaughter occurs when inspecting the carcass surface, or once the carcass has been divided into prime cuts or quarters. Sex and breed have no apparent influence on prevalence. The condition evidently occurs with equal frequency in steers, cows, and heifers. Virtually all striated muscles can be affected, including skeletal muscles, the muscles of the eye, larynx, and heart. In the USA, regulations require condemnation of BEM-affected parts, or (in severe cases) the entire carcass. These aesthetic considerations result in economic losses. Cattle experimentally infected with Sarcocystis have not shown BEM at slaughter. Here we review status of Sarcocystis species and BEM in cattle including prevalence, lesions, epidemiology, and association of BEM with different species of Sarcocystis.