Recent advances in biology and immunobiology of Eimeria species and in diagnosis and control of infection with these coccidian parasites of poultry

Avian coccidiosis, an intestinal disease caused by protozoan parasites of the genus Eimeria, occurs worldwide. It is considered to be one of the most economically important diseases of domestic poultry. For many years, prophylactic use of anticoccidial feed additives has been the primary means of controlling coccidiosis in the broiler industry and has played a major role in the growth of this industry, which now can produce about 7.6 billion chickens annually. However, development of anticoccidial resistance has threatened the economic stability of the broiler industry. Although there has been little effort by the pharmaceutical industry to develop new anticoccidials, the mounting problem of drug resistance of Eimeria species has prompted major research efforts to seek alternative means of control through increased knowledge of parasite biology, host response, and nutritional modulation. As a consequence, important advancements have been made, particularly in defining parasite antigens that have potential use in vaccines, defining the Eimeria genome, understanding the immunology of coccidial infections, and the practical applications of live vaccines. This review describes the progress in these areas, most of which has occurred within the past 10 to 15 years.