click image to zoom Swine genomic markers, phenotypes, chromosomes and genotyping are playing an increasingly important role in the latest efforts against porcine reproductive and respiratory syndrome (PRRS) virus. The science of genetics will play a vital role in the development of PRRS-resistant pigs and eventual elimination of the disease, according to Dr. Bob Rowland, professor of Diagnostic Medicine and Pathobiology, Kansas State University.
Rowland is executive director of the PRRS Coordinated Agricultural Project (CAP). The objective of the USDA-funded research program is to develop a roadmap for the eventual elimination of the PRRS virus.
The control and elimination of PRRS is likely the most challenging task facing the swine industry worldwide. Several factors related to the biology of the virus make disease detection and elimination extremely difficult.
In addition, PRRS control efforts are hampered by a lack of effective means to protect naïve herds from infection. Recent efforts have focused on regional initiatives intended to eliminate the costly disease from one specific geographic area at a time. One example of success is the Stevens County project in Minnesota, which has attained a PRRSV-negative status and has been expanded to include all of northern Minnesota.
“The PRRS virus is the most rapidly changing virus on the planet, plus it is stealthy, persistent and easily transmitted,” Rowland says. “The virus circulates very nicely within a production system. It might go away for a time but it keeps coming back.”
Regional control initiatives, air filtration of barns, and vaccine technology are important steps but there is no magic bullet in the battle against PRRS, Rowland says. “We need to bring all those things to bear if we are to win the battle against the disease.”
Rowland looks at PRRS not as an individual pig disease but as a population disease—one that causes economic loss by reducing herd performance. “All the infectious diseases in the history of swine production combined have had less economic impact than PRRS has had over the last 15 to 20 years,” he says.
The National Animal Health Monitoring System estimates that 21 percent of U.S. swine farms have the disease. Rowland believes up to 60 percent of farms have the virus.
Current research being conducted with the PRRS CAP centers around improvement in swine genetics, or improving the pig’s tolerance to the disease, according to Rowland. “Some pigs don’t care if they have the virus and maybe these are the type of pigs we should be breeding.”