Coccidia are protozoa, a group of very small, single-celled intestinal parasites. Moreover, they are obligate intracellular parasites, which means that living host cells are necessary to complete their life cycle. They have a simple, single-host developmental cycle and are transmitted via the fecal–oral route. The disease they cause is called coccidiosis and is widespread among newborn piglets worldwide. It occurs wherever pigs are kept indoors, and infections with these protozoa in pig herds pose a serious health and economic problem. In the past, controlling coccidiosis in piglets was difficult. Today, thanks to the availability of effective medicines, this problem can be fully controlled.
