Coccidiosis is one of the most common poultry diseases.
Coccidiosis is caused by protozoan parasites of the genus Eimeria. In poultry, Eimeria affects the intestine making it prone to other diseases (necrotic enteritis) and reducing the ability of this organ to absorb nutrients.
Between poultry houses, the disease is transmitted by mechanical carriers such as insects and wild birds. In general, good natural immunity is generated after Eimeria infections in poultry and for this reason, coccidiosis is usually a disease that affects young animals. However, the achieved immunity is specific for each of the species of Eimeria and it is not cross-protective between species
The replicative phases of the parasite lead to damage in the intestinal tissues. Individual birds may show no clinical signs or may suffer a mild loss of appetite, weight loss or decreased weight gain, diarrhoea (which can be bloody), dehydration and death. Resistance develops rapidly and infections can be self-limiting, but naïve birds which consume large numbers of oocysts can be severely affected and die. Immunity is strictly species-specific which means that birds exposed to one Eimeria remain susceptible to infection from all other species.