|ROWLAND, RAYMOND - Kansas State University
|DEKKERS, JACK - Iowa State University
Submitted to: Frontiers in Livestock Genomics
Publication Type: Review Article
Publication Acceptance Date: 9/10/2012
Publication Date: 12/14/2012
Citation: Rowland, R.R., Lunney, J.K., Dekkers, J. 2012. Control of porcine reproductive and respiratory syndrome (PRRS) through genetic improvements in disease resistance and tolerance. Frontiers in Livestock Genomics. 3:321.
Technical Abstract: Infections caused by porcine reproductive and respiratory syndrome virus (PRRSV) have a severe economic impact on pig production in North America, Europe and Asia. The emergence and predominance of PRRS in the 1990s are the likely result of changes in the pork industry initiated in the late 1970s. PRRS virus adaptations allow it to survive in modern commercial production system. PRRSC can cause severe clinical disease, maintain a life-long subclinical infection, and contribute to several polymicrobial syndromes. Current vaccines can lessen clinical signs, but are of little use for disease control and elimination. The relatively poor protective immunity following vaccination is a function of the virus’s capacity to generate a large degree of genetic diversity, combined with several strategies to evade innate and adaptive immune responses. In 2007, the PRRS Host Genetics consortium (PHGC) was established to explore the role of host genetics as a potential avenue for PRRS control. The PHGC model for PRRS incorporates the experimental infection of young pigs with well-characterized virus isolates. Groups of 200 pigs are infected and followed for 42 days after challenge, which encompasses both acute and persistent stages of infection. To date, 11 trials have been conducted using commercial pigs from a variety of breeding sources. Phenotypic disease traits include virus load and weight gain. Genome-wide association study (GWAS) incorporating a 60K SNP chip have identified a region on chromosome 4 (SSC4) associated with both weight gain and virus load. The region is near a family of genes involved in innate immunity. The results create the opportunity to develop breeding programs that will produce pigs with increased resistance to PRRS. Other avenues of study within the PHGC are the definition of genetic factors related to disease tolerance and improved response following vaccination.