A murine Sarcocystis that causes an Isospora-like infection in cats.

Sarcocysts similar to those of Sarcocystis muris were found in mice from the Iowa State University Mouse Genetics Laboratory. Muscle tissue from these mice was fed to 8 cats. Five cats developed an isosporan infection with oocysts most like those of Isospora felis. Sporulated oocysts from cat feces were fed to mice. In about 100 days mice developed sarcocysts that were visible to the unaided eye. Three cats were fed muscle tissue from the experimentally infected mice, and all cats developed an I. felis-like infection. Three cats fed muscle tissue from control mice from the same colony as the experimental mice did not develop isosporan infections. Thus it is demonstrated that this murine Sarcocystis is part of an isosporan life cycle.