Answer to Case of the Week 530: Sarcocystis sp.; either S. hominis or S. suihominis
Thanks again to Idzi Potters and the Institute of Tropical Medicine, Antwerp, for sharing this case with us. I haven't featured intestinal sarcocystosis on this blog before, and so having these great photographs is a real treat. As Old One, Florida Fan, Blaine and others noted, humans serve as the definitive host for the intestinal form of sarcocystosis and shed sporulated oocysts and sarcocysts in their stool. Both forms are seen in this case:
Rarely, humans may also serve as the intermediate host for some Sarcocystis species when ingesting oocysts or sporocysts in contaminated food or water. In this form of disease, sarcocysts form within various muscles in the body, causing transient myalgias, muscle weakness and associated edema. HERE is what a sarcocyst looks like in skeletal muscle (a case of S. cruzi; not a human pathogen).