PRRS solution still evades researchers

EDMONTON — Porcine reproductive and respiratory syndrome is among the most economically important diseases affecting commercial pig operations.

Known as PRRS, this virus probably costs Canadian producers $100 million a year and is difficult to control because of its evolving nature. It causes respiratory disease in newborns and growing pigs as well as reproductive failure in pregnant sows. It has a significant impact on animal welfare and a farm’s economic viability.

“Vaccines have really only been partially effective. They are available and they are used, but PRRS is still a major problem,” Paul Stothard of the University of Alberta said during an infectious disease conference held at the university May 2-3.

“Genetics have been recognized for some time in determining how well animals do when they get infected with PRRS.”

Researchers are undertaking genomic analysis because they know that some breeds of pigs are more susceptible than others.

For example, Durocs seem to be more susceptible to the PRRS virus, while Meishan pigs from China suffer less.

Researchers have learned that chromosome differences have a significant influence on how infected pigs might handle the disease.

Scientists have now started a genome-wide search to explain the variability in resilience to PRRS.

The identified markers could ultimately lead to improved animal selection, but more work is needed to see what makes these genes respond the way they do, said Stothard.

Ziqi Yang, a doctoral candidate at the university, said pigs may pick up a disease, but then secondary infections develop.

She is comparing sick and healthy pigs to see if there is a genetic difference. The next step is looking for biomarkers that can identify animals that are better able to respond to this mixed disease challenge.

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