Coccidiosis affects most species of poultry, waterfowl, gamebirds, and pigeons. The information presented here will focus on the small chicken flock but the principles discussed are generally applicable to other species. Affected birds will be depressed, have ruffled feathers, be reluctant to move, and often the feathers around the vent will be soiled with fecal material due to diarrhea. In severe cases bloody droppings may be observed. Lesions A postmortem examination of a bird that has succumbed to coccidiosis will reveal distinct pathology in one or more regions of the intestines.
Coccidial species are both highly host specific and infect a specific region of the intestines.
Nine species of coccidia infect chickens, three of these are most commonly associated with severe disease. E. tenella infects the ceca of the chicken and severe hemorrhage is seen in the cecal lumen with caseous cecal cores developing in more chronic cases. Birds that recover from coccidiosis develop short lived species specific immunity. With constant exposure to coccidial oocysts in the environment, previously infected chickens do not develop clinical disease. Different avian species have different, host specific, Eimeria spp.