The wisent (Bison bonasus, Bovidae) as an intermediate host of three Sarcocystis species (Apicomplexa: Sarcocystidae) of cattle.

Sarocysts were found in muscle tissue of a wisent (Bison bonasus) which was born and kept in Germany. Light microscopic and TEM examination revealed all the three named species known from cattle: Sarcocystis cruzi ("thin-walled", with longer hair-like villar protrusions of the primary cyst wall); S. hirsuta ("thick-walled", with tongue-like protrusions of the cyst wall arising with very short and narrow stalklets from the surface of the cyst and containing rows of electron-dense granules in the core); and S. hominis ("thick-walled", with finger-like protrusions of the cyst wall not constricted at their base and containing few or no electron-dense granules). So far, only S. cruzi was known to occur in Bison bison in North America. The findings in the wisent strikingly support a modified conception of the intermediate host specificity in Bovinae. In this connection the identity of S. cruzi and S. poephagicanis is suggested as well as that of S. hirsuta and S. poephagi.