Prepatent and patent periods, and production and sporulation of oocysts of Eimeria subspherica isolated in Japan.

Eight calves were inoculated with 10(6) or 10(7) sporulated oocysts of Eimeria subspherica, Christensen, 1941. All the calves, except one, were successfully infected. Prepatent period was 10 to 11 days with a mean of 10.6 days and patent period was 1 to 5 days with a mean of 2.9 days. Peak oocyst discharge was found on days 11 and 12 after inoculation. The number of oocysts passed in the feces was very small and varied among calves, and no relationship was detected between the inoculum dose and the number of oocysts passed in the feces. No clinical symptoms were associated with the infection in any calves. Infectivity, reproductive potential and pathogenicity of E. subspherica were suggested to be low in the experimentally infected calves, even though relatively large numbers of oocysts were given. The sporulation process of E. subspherica oocysts was observed under a condition of 29 degrees C with constant aeration. Completely sporulated oocysts increased in percentage following a sigmoid curve, and the expected 50% and 95% sporulation times were determined as 161 and 194 hours, respectively, by regression analysis.