Genomic Analysis of the Susceptibility to Porcine Circovirus 2b

Porcine Circovirus type 2 (PCV2) is the causative agent of Porcine Circovirus Associated Diseases (PCVAD) that impact growth and has the potential to lead to mortality. Host genetics and co-infection play crucial roles in disease progression. Various crossbred lines were experimentally infected with PCV2b to identify major genetic variations that influence important indicators of disease progression and immune response.  During the 28-day challenge period, weekly measures of weight gain, viral load and specific antibody levels were obtained. The initial results provide evidence of host variation in magnitude and time of immune response to PCV2b. A higher viral load was correlated with slower growth (r = - 0.29) and higher levels of PCV2 antibodies, IgM (r = 0.32 to 0.43) and IgG (r = 0.30 to 0.43). A genome-wide association study that included the genotypes of 56,433 SNPs was used to uncover genomic regions that influence the variation of the measured phenotypes. Major clusters of SNPs that impacted viral load were located on multiple chromosomes including SSC6, SSC7 and SSC12. The region located on SSC7 also affected weight gain during challenge. The cluster of genes of the Swine Leukocyte Antigen class II is located in this region and could explain the observed phenotypic variation. This study provides an extensive data set that will be used to determine genes and genetic variants associated with PCVAD susceptibility. Selection based on DNA markers associated with disease susceptibility has the potential to improve animal welfare as well as to reduce economic loss.