Submitted to: Parasitology International Congress
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/1994
Publication Date: N/A
Technical Abstract: The ingestion of food and water contaminated with oocysts from infected cat feces or the ingestion of tissue cysts from infected meat are the 2 major sources of Toxoplasma gondii infection in humans. At present there are no subunit or killed vaccines for immunization of farm animals or humans for toxoplasmosis. A live vaccine containing tissue cysts or bradyzoites of a mutant strain of T. gondii (T-263) is being developed for marketing in the U.S. This vaccine, when given orally to cats, prevents the formation of oocyts. Vaccines that reduce the number of tissue cysts in farm animals are needed. Recent studies indicate that vaccination of farm animals with nonpersistent strains of T. gondii is possible and could reduce parasite burdens and prevent damage to the fetus. Another strategy to minimize transmission of T. gondii to humans is to kill tissue cysts in meat. Tissue cysts of T. gondii in meat are rendered noninfective by cooking to an internal temperature of 66oC, by freezing at -12oC for 1 day, and by exposure to 50 kilorads gamma-irradiation (Cesium-137).