Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 1999
Publication Date: N/A
Interpretive Summary: Coccidiosis is an intestinal infection caused by intracellular protozoan parasites which belong to several different species of Eimeria. Coccidiosis seriously impairs the growth and feed utilization of livestock and poultry. Drugs are currently used to control coccidiosis. However, due to the increasing incidence of drug-resistant strains of field coccidia, a novel control strategy is needed. Since the life cycle of the organism and the host immune responses to coccidia parasites are complex, the coccidia vaccine development has been difficult. Thus, a better understanding of how the host immune system interacts with the parasites will enhance our chances for the development of a new control strategy. In this presentation, an ARS scientist summarizes a new development in chicken immunology which is pertinent to the intestinal response to coccidia. This information will help the industry and the poultry scientists to develop a new control strategy against coccidiosis.
Intestinal parasitism is a major stress factor leading to malnutrition and lowered performance and production efficiency of livestock and poultry. Coccidiosis is an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria. Infection with coccidia parasites seriously impairs the growth and feed utilization of chickens and costs the US poultry industry more than $1.5 billion in annual losses. Although acquired immunity to Eimeria develops following natural infection, due to the complex life cycle and intricate host immune response to Eimeria, vaccine development has been difficult and a better understanding of the basic immunobiology of pertinent host-parasite interactions in necessary for developing effective immunological control strategies against coccidiosis. Chickens infected with Eimeria produce parasite specific antibodies in both the circulation and mucosal secretions but humoral immunity plays only 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 avian intestinal immune system and its response to Eimeria as well as provide a conceptual overview of the complex molecular and cellular events involved in intestinal immunity to coccidiosis. It is anticipated that increased knowledge on the interaction between parasites and host immunity will stimulate the birth of novel immunological and molecular biological concepts in the control of intestinal parasitism.