Development of a Live Vaccine Against Ovine Toxoplasmosis

A vaccine has been developed using strain S48, which has lost the ability both to form tissue cysts in intermediate hosts and oocysts in the cat. The tachyzoites, cultured in vitro, are injected intramuscularly into ewes at least 4 weeks prior to mating and provide good protection against abortion and barrenness. Safety and efficacy trials are discussed.