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USDA Scientists Make Breakthrough in PRRS Research

This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from the USDA’s rich science and research portfolio.

Porcine reproductive and respiratory syndrome (PRRS) is a disease that costs the U.S. pork industry an estimated $664 million per year. Recently, scientists have made a breakthrough in research efforts to curb the disease.

A consortium of scientists from around the country, with funding from USDA’s National Institute of Food and Agriculture (NIFA) and Agricultural Research Service (ARS), have discovered a genetic marker in pigs that identifies whether or not a pig has reduced susceptibility to PRRS.

The researchers found a genetic marker, called a quantitative trait locus, on swine chromosome 4 that is associated with resistance to PRRS virus infection. According to Joan Lunney, a research scientist at ARS in Beltsville, Md., this is especially important as this location also is associated with improved growth of pigs that are infected with the PRRS virus. She says results indicate a positive effect for PRRS resistance and higher weight gain.

ARS scientist Joan Lunney prepares genomic DNA samples from pigs for analysis. Photo credit: ARS

ARS scientist Joan Lunney prepares genomic DNA samples from pigs for analysis. Photo credit: ARS

The identification of this marker gene will help animal breeders increase the frequency of  PRRS-resistant pigs in their herds. In addition, this research could be used to help decrease the impact of PRRS and also help researchers find similar genes responsible for resistance to other diseases.

The research team that led to this marker discovery includes Lunney at ARS, Bob Rowland at Kansas State University and Jack Dekkers at Iowa State University. The researchers continue to be funded by NIFA, ARS, the PRRS Host Genetics Consortium – a nationwide effort originally funded by the National Pork Board, and the U.S. Swine Genome Coordinator for the National Animal Genome Research Program.

To obtain the data necessary for the marker research, researchers collected blood and tissue samples, along with weight‐gain data, from 600 PRRS Host Genetics Consortium pigs at biosecure facilities at Kansas State University. From there, ARS researchers prepared genomic DNA at the facilities in Beltsville for genotyping at a commercial lab. Finally, Iowa State University researchers used the resulting data to search the entire genome of the 600 pigs. They worked to identify chromosomal segments common to pigs that had lower levels of PRRS virus circulating in their blood and that grew faster after PRRS infection.

Now that scientists have found a chromosomal segment that can signify resistance to PRRS, the next step is to pinpoint the gene and determine whether it shows the same effects for other strains of the PRRS virus.

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