Abstract: A new mutant strain vaccine, and a corresponding method of immunization, against Toxoplasma in cats is provided which makes use of a reproductively deficient strain of T.gondii, designated T-263. Bradyzoites in tissue cysts from laboratory animals infected with the mutant were fed to cats, which developed immunity against subsequent T.gondii challenge without concomitant shedding of infectious oocysts. The new vaccine eliminates the need for chemoprophylaxis subsequent to primary infection.

Abstract: A method of immunizing cats against shedding of Toxoplasma oocysts is described wherein cats are given a primary Toxoplasma infection, preferably by feeding of tissue cysts, and are chemoprophylactically treated to suppress oocyst shedding as a result of the primary infection. thus, the treated cats are given immunity to oocyst shedding without the necessity of initial shedding. The treating agent is preferably monensin given with the cats' daily ration at a level of at least about 200 mg. monensin per kg. of cat food. Other useful treating agents include salinomycin or a combination of orally administered sulfadiazine and pyrimethamine.

Abstract: A method for the immunization of mammals (including man) and birds, against Toxoplasma gondii is described which involves subcutaneous administration of a live, low-virulent vaccine comprising a temperature-sensitive mutant of the persistent, virulent RH strain of T. gondii. The vaccine gives immunity against subsequent challenge, but does not persist and does not cause chronic infection of the subject and which therefore cannot result in illness or death in the event that the subject later becomes immunosuppressed.

Abstract: A method of preventing, or at least substantially minimizing, shedding of Toxoplasma oocysts by cats is described which can be begun after infection of the cat and may serve to reduce the contamination with infectious oocysts of soils around areas of human habitation. The method involves administration, in effective amounts of a drug agent selected from the group consisting of monensin or salinomycin. The administration is preferably oral, and can be accomplished by mixing the drug with the cat's food or via a slow release dosage form. The drug treatment is normally commenced within about two days after infection, and is continued for a period of at least about two weeks.