Life Cycle and Types of Coccidia

Knowing how coccidia develop helps to understand and control the disease. Coccidiosis is caused in poultry by a one-celled parasite of the genus Eimeria. The life cycle of Eimeria takes about four to seven days to complete. It begins when active “oocysts” are picked up by the bird and swallowed. An “oocyst” is a capsule with a thick wall protecting the parasites. They “sporulate” or become infective if moisture, temperature, and oxygen become conducive to growth. After a bird eats the oocysts, coccidia imbed in the intestinal lining and multiply several times, damaging tissue.

Coccidia are parasites, so they get their nutrients from the chicken host. The multiplications eventually stop, usually before causing death of the bird. The bird sheds the parasite in its droppings. These new oocysts can infect other birds. See the box “Coccidial Multiplication” for further details on coccidia’s complex life cycle.

Coccidiosis is usually a disease of young birds, but birds can be infected at any time if never before exposed. Coccidia populations take time to build to dangerous levels, therefore outbreaks usually occur when birds are between 3 and 8 weeks of age. Coccidiosis goes hand-in-hand with gut diseases, because it damages the gut and allows bacteria to enter and cause secondary infections. Coccidia are “species-specific” – coccidia that affect chickens do not affect other livestock, and vice versa (see Species-Specific Parasites box).