There are many important species of coccidia that effect many animals especially mammals and birds. The most common genera are Eimeria and Isospora. Sporozoites penetrate intestinal cells, feed, grow and eventually go through a-sexual reproduction called schizogony. The end result of this division is the production of merozoites which rupture from the infected cell and enter new cells. At some point, some merozoites begin the sexual phase of the life cycle, being micro and macro-gametes.
Fertilization occurs and a zygote is produced within the host cells.
In all instances, the number of asexual cycles is pre-determined. Pathogenesis is related to intestinal cell distruction. Fever is not common unless secondary infection occurs. Bloody diarrhea is common in some infections with a resulting anemia. In general, the disease caused by coccidia varies not only with the state of the host, but with the species of coccidia, the degree of parasitism, and the site of infection.