Mapping resistance to bacteria and viruses in the chicken

Salmonella and Campylobacter are major zoonotic bacterial pathogens. The vast majority of human cases arise from the consumption of infected poultry. One sustainable solution would be to reduce contamination of poultry by identifying disease resistance genes. Resistance to colonisation with either Salmonella or Campylobacter is partly genetically determined. Inbred lines of chickens, 61 and N, are respectively resistant and susceptible to colonisation with either Salmonella or Campylobacter. Using a backcross and a high density genome-wide SNP panel, we have identified 4 resistance QTL for each colonisation model, one of which is in common. Marek's disease virus is a highly contagious, cell-associated, oncogenic  -herpesvirus. We have carried out the most comprehensive gene expression study to date on MDV, using Affymetrix chicken whole genome arrays which also contain 684 transcripts from 17 avian viruses. As well as analyzing the host response to infection in both resistant (61) and susceptible (72) lines, and inherent expression differences between the two lines, we also analysed alterations in viral gene expression following infection. Our assumption was that genes controlling disease resistance would be involved during the initial stages of infection, during the induced innate response to infection, and thus we concentrated on responses on 2, 3 and 4 dpi. Comparison of our gene expression data with previous QTL data allowed us to identify genes as candidates for involvement in resistance to MD, and these were then analysed for SNPs which correlated with resistance - in other words, potential causative mutations for MD resistance/susceptibility.