Submitted to: Coccidiosis International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 30, 1998
Publication Date: N/A
Interpretive Summary: Avian coccidiosis is caused by several different species of Eimeria which infect the intestine of chickens. Currently drugs are used as the major control strategy. However, due to increasing drug resistant strains of Eimeria parasites, alternative control strategies are needed. In this review article, the ARS scientist summarizes the current knowledge on chicken immune system and host immune response to coccidian parasites. Specifically, role of various lymphocytes and lymphokines are discussed. This article will enhance our understanding of the chicken immune system and facilitate the development of novel control strategies against coccidiosis.
Development of a vaccine for avian coccidiosis has been hampered by the lack of understanding of the various components of host immune system leading to protective immunity. A clear understanding of the cellular dichotomy in cytokine production in mice and the availability of immunological reagents, as well as gene knock-out mice, now makes in- depth immunological study in chickens feasible. From studies of various parasitic infection models in mice, it is becoming clear that complex regulation by cytokines is involved in host immunity. Furthermore, the studies in mice clearly indicated an important role of various effector mechanisms involving T lymphocytes, macrophages, NK cells and cytokines in resistance to coccidiosis. In comparative studies of coccidiosis in chickens, in vivo and in vitro studies revealed that interferon-gamma, tumor necrosis factor and transforming growth factor-beta are induced following Eimeria infection. Depletion studies revealed the importance of CD8+TCRalpha,beta+ T lymphocytes in host protective immunity to avian coccidiosis. Taken together, studies in mice and chickens are providing a better understanding of the role of effector cells and soluble factors which control immune responses to Eimeria parasites.