Some aspects of Leucocytozoon caulleryi reinfection in chickens.

The role of first- and second-generation schizonts in acquired immunity to Leucocytozoon caulleryi in chickens was studied. The chickens, which had recovered from a primary infection with various doses of sporozoites at 22-95 days of age, were challenged with sporozoites. First-generation merozoites were found in all of the challenged chickens, but no second-generation merozoites and gametocytes were seen in 30 of 32 chickens challenged with sporozoites. Almost all of the chickens that had recovered from a primary infection with sporozoites showed complete resistance to reinfection, and those that had recovered from a primary infection with first-generation merozoites showed resistance to reinfection with sporozoites. These results indicate that the second-generation schizont of L. caulleryi appears to be more immunogenic than the first-generation schizont and that some immune factors acquired by the chickens in the second generation of schizogony may inhibit the development of second-generation schizonts.