Sarcocystis muris Infection

Cats are the definitive host for S. muris, and mice serve as the only intermediate host for this coccidian parasite. Infection of mice occurs through ingestion of oocyts in cat feces, but can also be sustained within a mouse population through cannibalism. Sarcocystis organisms have been observed in the diaphragm, heart, and skeletal muscle of naturally infected laboratory mice, possibly exposed through contamination by cat-owning techni­cians rather than food contamination. The authors are also aware of S. muris in skeletal muscle of mice main­tained for toxicology studies. It has been found that SCID mice can also serve as definitive hosts for S. muris, with fecal shedding of oocysts.