It is one of the most common human parasites in the world. The organism was first discovered in the gundi, a North African rodent. The three forms of T gondii are oocysts, trophozoites, and tissue cysts. Oocysts Only members of the cat family shed oocysts. Cats become infected by ingesting either oocysts from fecal contamination or tissue cysts present in the flesh of eaten animals.
Digestive enzymes release the organisms, which invade the feline small intestine.
Reproduction results in development of millions of noninfectious, unsporulated oocysts excreted in feces of cats for up to 2 weeks. Once outside the cat s body, sporogony occurs for up to 21 days, resulting in development of infectious oocysts. In warm, moist soil, these oocysts can remain viable for more than 1 year. Trophozoites Tachyzoites are the actively proliferating trophozoites, which are observed during the acute stage of infection. Tachyzoites can be found in any organ but occur most commonly in the brain, skeletal muscle, and heart muscle.