Antigens of Toxoplasma gondii that provide specific and strong delayed type hypersensitivity (DTH) immune response, or which stimulate IFN-y secretion, are used for testing subjects for infection. Any skin testing format may be adapted for testing for the delayed type hypersensitivity, including a patch, a needle, or a prong. Presence of DTH indicates infection. Alternate methods of detecting a T cell response including monitoring IFN-y secretion may be used.