Eimeria is a genus of Apicomplexan parasites that includes various species responsible for the poultry disease coccidiosis. Medications are available for the parasite; however, drug resistance is common as well as possible drug residues in the meat once the animal is butchered. Vaccines have been developed but one vaccine will only cover one species and not others. So far the best practice is to vaccinate the chicks once they hatch from the egg so they are immune for life. Symptoms of Eimeria infection include bloody diarrhea due to intestinal epithelium dying off since a large number of oocysts and merozoites burst out of the cells. Necrotic tissue clogs the cecum causing the organ to die.