Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: December 1, 2002
Publication Date: January 10, 2003
Citation: Pinard-Van Der Laan, M.H., Lillehoj, H.S., Zhu, J.J. 2003. Disease resistance and transmission. Genetic resistance and transmission of avian parasites. In: Muir, W.M., Aggrey, S.E. Aggrey, editors. Poultry Genetics, Breeding and Biotechnology. United Kingdom: CABI Publishing. p.329-356.
Interpretive Summary: Understanding avian immune system and host genetic factors which influence disease resistance in poultry is becoming important since prophylactic medications which are used to control poultry diseases are becoming less effective. In this book chapter, scientists at the Institute of National Research Agriculture in France and ARS reviewed current knowledge on immunopathology of avian coccidiosis and discuss strategies to combat them. Since coccidiosis is controlled by host genetic factors as well as immunological factors, various strategies which will identify genes controlling disease resistance in poultry is discussed. This review provided an up-to-date summary of research findings in avian coccidiosis which will help poultry scientists and industry to gain new insights into the cellular and molecular mechanisms of disease process in avian coccidiosis.
Avian coccidiosis is becoming increasingly difficult to control for the poultry industry as a consequence of two factors, resistance to chemoprophylaxis and confined rearing conditions. Although in-feed medication of broilers has been commonly used to control coccidiosis in the past decades, drug-based control measures are costly to the industry and are becoming increasingly ineffective as the resistant strains of Eimeria develop. Furthermore, increasing public concern over the presence of chemical residues in the food supply is demanding a non-drug mediated control strategy for poultry diseases. In view of rapid development of new biotechnology in veterinary science, novel control strategies using genomics, molecular biology and immunology would offer an alternative way to prevent the spread of coccidiosis in the future. Genomics approach includes mapping the quantitative trait loci and the identification of candidate genes, which control coccidiosis resistance and susceptibility whereas molecular and immunological-based methods include vaccination, immunostimulation with cytokines, and development of chicken strains with increased innate immunity. For any of these measures to be successfully applied in the commercial setting, fundamental understanding of avian genomics and host intestinal immune system is required. Increasing evidence for the protective role of local immune response and various effector molecules as has been described in recent reviews (Lillehoj et al., 2000a; Yun et al., 2000a) provide optimism that novel means to control coccidiosis is in the near future.
The aim of this chapter is to present an introductive summary on immunopathology of avian coccidiosis and strategies to combat them. Evidence for genetic resistance to coccidiosis will be then presented. By reviewing experiments studying genetic resistance, the different criteria used for assessment of disease resistance will be discussed and attention will be drawn on the effect of major histocompatibility on resistance. Finally, strategies and first results of two QTL mapping experiments will be presented.