Submitted to: Journal of Korean Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 17, 1999
Publication Date: N/A
Interpretive Summary: Parasites which infect the intestine cause significant economic losses to the poultry industry since the infection can cause a malabsorption of the nutrients and also poor feed utilization. The ARS scientists have been studying coccidiosis, a disease caused by the protozoan parasite called coccidia, to develop a new control strategy against this parasites. Coccidiosis costs the industry more than $600 million annually in prophylactic treatment. Drugs have been used to prevent coccidiosis. However, with the increasing concerns over the development of drug- resistant coccidia parasites in the field, a new control strategy is critically needed. In this presentation, the recent developments about the novel concepts in controlling coccidiosis based upon immunity, dietary manipulation and genetics will be discussed. The authors also review the current understanding of how the various nutrients improve the host disease resistance against coccidiosis and summarize the new knowledge on the host response to coccidia. The knowledge which is presented in this paper will enhance the feasibility of developing a new control strategy for intestinal parasitism and will reduce the major stress factor that can lead to a lowered performance and a lowered production efficiency in livestock and poultry.
Coccidiosis, an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria seriously impairs the growth and feed utilization of livestock and poultry. Due to the complex life cycle of organism and intricate host immune responses to Eimeria, coccidia vaccine development has been difficult. Understanding of basic immunobiology of pertinent host-parasite interactions is necessary for the development of novel control strategy. Although chickens infected with Eimeria spp. produce parasite-specific antibodies in both the circulation and mucosal secretions, antibody mediated responses play a minor role in protection against coccidiosis. Rather, increasing evidence shows that cell-mediated immunity plays a major role in resistance to coccidiosis. T-lymphocytes appear to respond to coccidiosis both through cytokine production and a direct cytotoxic attack on infected cells. The exact mechanisms by which T-cells eliminate the parasites, however, remain to be investigated. Since it is crucial to understand the intestinal immune system in order to develop an immunological control strategy against any intestinal diseases, this presentation will summarize our current understanding of the avian intestinal immune system and mucosal immune responses to Eimeria, to provide a conceptual overview of the complex molecular and cellular events involved in intestinal immune responses to enteric pathogens.