Evidence for genetics susceptibility to PRRSV infection

Porcine reproductive and respiratory syndrome (PRRS) is a major cause of economic loss for the swine industry worldwide and in the intensive pig industry, control of infectious diseases is a major production challenge. Approaches applied to achieve disease eradication include various control measures designed to reduce infection pressure within the herd, e.g. management changes and vaccination, however, no system has proved to be efficient up to now. Identification and characterization of chromosomal regions with significant effects on PRRS resistance is important because might allow to use genomic variation in selective breeding program. We have created a long-term resource database combining pedigree data and phenotypes for health and production traits, and an extensive biorepository (MISAGEN) of about 5,000 purebred animals from 18 genetically connected commercial farms in Northern Italy. Pig were monitored from bird up to 60-100 day. The heritability of PRRS viremia observed was 0.096. The selected population comprised 1,208 pigs across four breeds (Large White, Landrace, Duroc and Pietrain). Genomic DNA was genotyped with the Porcine SNP60 SNPchip for genome wide association studies (GWAS) for the PRRS viremia measured by PCR in sera of weaning piglets. After editing, 47,446 markers and 1,127 individuals were available. The GRAMMAR methodology was used for the analyses. This GWAS analysis identified seven SNPs well above the genome-wide 5% significance threshold, of which five could be mapped to known chromosomal locations of the pig genome sequence (Build9). To refine the phenotyping we measured the antibody response to PRRSV with Elisa during two growth phases in all the genotyped animal. Work is in progress to define new phenotypes to be eventually used in new GWAS analysis.