Immunization of cats with tissue cysts, bradyzoites, and tachyzoites of the T-263 strain of Toxoplasma gondii.

Previous studies have demonstrated that oral administration to cats of tissue cysts of the oocystnegative mutant strain of Toxoplasma gondii, T-263, induces immunity to oocyst shedding following challenge. Experiments were designed to compare the levels ofprotection induced by T. gondii T-263 when tissue cysts, bradyzoites released from tissue cysts, and tachyzoites were administered to cats. In I experiment, groups of cats received 2 oral doses of intact tissue cysts or released bradyzoites of T. gondii T-263 and were challenged 47 days later with the oocyst-producing strain of T. gondii T-265. All cats seroconverted following immunization and none of them shed oocysts following challenge