Association study in naturally infected helminth layers shows evidence for influence of interferon-gamma gene variants on Ascaridia galli worm burden

Single nucleotide polymorphisms (SNPs) in the genes for interleukin-4, -13 and interferon-gamma, and 21 additional SNPs which previously had been significantly associated with immune traits in the chicken, were genotyped in white and brown layer hens and analyzed for their association with helminth burden following natural infections. A nucleotide substitution located upstream of the promoter of the interferon-gamma gene was significantly associated with the log transformed number of Ascaridia galli in the brown layer line (genotype CC: 6.4 ± 1.0 worms; genotype CT: 11.7 ± 2.2 worms). Therefore, IFNG seems to be a promising candidate gene for further studies on helminth resistance in the chicken.