Coccidia: a review of recent advances on immunity and vaccine development.

The genus Eimeria contains a number of obligate intracellular protozoan parasites with a complicated life-cycle involving both asexual and sexual stages of development. Coccidiosis is caused by Eimeria infecting primarily the intestine of the susceptible host, thereby seriously impairing the growth and feed utilization of poultry and other livestock. The desire to develop a vaccine against Eimeria has promoted active research to elucidate the mechanisms of protective immunity and identification of candidate vaccine antigens. Protozoa are unique in their modes of transmission and nature of disease manifestations, the significance of which should be considered in the development of a control strategy. An intricate and complex interplay of different cell populations and cytokines is involved not only in the pathogenesis of coccidiosis, but also in the development of protective immunity. Thus, comprehensive understanding of the events leading to protection following Eimeria infection will be crucial for the development of an effective vaccine.