Toxoplasma gondii is a widely disseminated parasite which is capable of infecting all warm-blooded vertebrates to different degrees of severity, depending on the species infected. Toxoplasma gondii is a zoonotic disease and, as such, a successful vaccine would have beneficial impacts in both medical and veterinary fields. An effective vaccine for use in humans, while serving in the first instance to reduce mortality and morbidity associated with infection, would also have economic benefits, as it would reduce the financial burden of lifelong care needed for those with severe chronic disease. The ideal vaccine for veterinary use would have the dual advantages of increasing livestock productivity while reducing the public health risk associated with eating meat. The chapter defines the problems associated with toxoplasmosis in different economically important livestock animals, such as sheep, goats, pigs, cattle, and chickens, and in the definitive host species, the cat.