Apicomplexan parasites of the genus Eimeria are organisms which invade the intestinal tract, causing coccidiosis, an enteric disease of major economic importance worldwide. The disease causes high morbidity ranging from an acute, bloody enteritis with high mortality, to subclinical disease. However, the presence of intestinal lesions depends on the Eimeria species. The most important poultry Eimeria species are: E. tenella, E. necatrix, E. acervulina, E. maxima, E. brunetti, E. mitis, and E. praecox. Key points to better understanding the behavior of this species are the host-parasite interactions and its life cycle. The present paper reviews the literature available regarding the life cycle and the initial host-parasite interaction. More studies are needed to better understand these interactions in poultry Eimerias, taking into account that almost all the information available was generated from other apicomplexan parasites that generate human disease.

Avian coccidiosis is the most costly global poultry parasitic disease, which represents a threat to food production and sustainability. Coccidiosis is still ubiquitous even in modern poultry production systems. Protective immunity against coccidia does develop but differs for each Eimeria species and depends on the method of immunization and the immune response (including both early innate immune response by several proteins and professional phagocytes as well as acquired immune response with specialized cells). In addition, GALT is a master tissue in the immune response against coccidiosis because of its crucial functions: acquired immunity in both the cellular and humoral immune responses. Here, we present an extensive review on the immune response against coccidiosis and the use of vaccines as an alternative for consideration in integrated sustained coccidiosis control programs.