Intestinal immune responses to coccidiosis

Intestinal parasitism is a major stress factor leading to malnutrition and lowered performance and production efficiency of livestock and poultry. Coc cidiosis is an intestinal infection caused by intracellular protozoan paras ites belonging to several different species of Eimeria. Infection with cocc idia parasites seriously impairs the growth and feed utilization of chicken s and costs the US poultry industry more than $1.5 billion in annual losses . Although acquired immunity to Eimeria develops following natural infectio n, due to the complex life cycle and intricate host immune response to Eime ria, Vaccine development has been difficult and a better understanding of t he basic immunobiology of pertinent host-parasite interactions is necessary for developing effective immunological control strategies against coccidio sis, Chickens infected with Eimeria produce parasite specific antibodies in both the circulation and mucosal secretions but humoral immunity plays onl y a minor role in protection against this disease. Rather, recent evidence implicates cell-mediated immunity as the major factor conferring resistance to coccidiosis. This review will summarize current understanding of the av ian intestinal immune system and its response to Eimeria as well as provide a conceptual overview of the complex molecular and cellular events involve d in intestinal immunity to coccidiosis, It is anticipated that increased k nowledge of the interaction between parasites and host immunity will stimul ate the birth of novel immunological and molecular biological concepts in t he control of intestinal parasitism. (C) 2000 Elsevier Science Ltd. All rig hts reserved.