Authors

M Nolan¹; K Boulton²; F Tomley¹; D Hume²; D P Blake¹;  ¹ Royal Veterinary College;  ² The Royal (Dick) School of Veterinary Studies and the Roslin Institute, The University of Edinburgh

Discussion

Eimeria are parasites of major importance to the poultry industry. A reduced portfolio of control options has stimulated research seeking alternate solutions, including breeding birds with greater resistance/tolerance to disease. Here, 1200 broilers were subject to Eimeria tenella challenge. A genome-wide association study (GWAS) assessed genetic variance in response to infection for percentage body weight gain (%BWG), caecal lesion score (CLS), and serum interleukin 10 (IL10). E. tenella challenge resulted in significant phenotypic variation in response to infection in all traits. Eigenanalysis defined the relationships among the different components of the response. The first Eigenvector classified correlations to reflect differential susceptibility to the pathology associated with infection. The second revealed resistance is not the inverse of susceptibility. A third identified a subpopulation of birds that were tolerant in the face of severe inflammation with little or no IL10 response to severe caecal injury, and good maintenance of %BWG. GWAS identified suggestive genome-wide significant SNPs associated with CLS and IL10, while a chromosome-wide SNP was located for %BWG. Pathway analysis identified candidate genes putatively responsible for each trait. Visualisation of Eigenvectors provides a valuable insight into variation in the immune responses of animals to diseases and, in conjunction with GWAS, may identify biomarkers to support breeding programs.