The early development of immunity to Eimeria maxima in comparison with that to Eimeria tenella

Immunity to Eimeria maxima, judged by oocyst production resulting from a low challenge inoculum, was evident when the challenge was given as early as 3 days after the immunizing dose of 250 or 500 oocysts. Immunity was complete, i.e. no oocysts were produced, to challenge at 7 days after an initial inoculum of 500 oocysts, or at 14 days after 250 oocysts. Judged by the above criteria 250 oocysts of E. tenella did not induce immunity to challenge given at 3, 5, 7 or 14 days. The findings are discussed.