Depending on the Eimeria species, the coccidian lifecycle takes approximately five to eight days to complete.
Stage 1 : Unsporulated oocysts are shed in the feces in the litter. Oocysts sporulate (become infective) in the presence of adequate moisture, oxygen and temperature. Oocysts are extremely environmentally resistant and can survive up to one year in dry, cool environments.
Stage 2 : Sporulated oocysts, containing four sporocysts that each contain two infective sporozoites, are ingested by the birds from ground and litter pecking.
Stage 3 : Sporocysts and then sporozoites are released in the gut from the sporulated oocyst by excystation, a process facilitated by the physical grinding effect and the presence of digestive enzymes and bile salts.
Stage 4 : The sporozoites penetrate the gut cells to initiate development of asexual intracellular schizonts. Schizonts produce large numbers of a second invasive stage, called merozoites that penetrate other gut cells to produce a further generation of schizonts.