Despite good success in controlling and reducing PRRS in North America, the virus continues to be a leading cause of illness among sows, says Dr. Tim Loula. “PRRS has been the major health challenge in the industry since the 1980s,” said Loula, a veterinarian working out in the Swine Vet Center in St. Peter, Minnesota.

Loula was in Winnipeg on January 30 to address producers attending Manitoba Swine Seminar 2008.  This past winter, he reported, a large percentage of the American

Midwest was infected with PRRS and there was an outbreak in China in January.  He noted that outbreaks are worse in winter. Among the effects of the disease, Loula listed lower litter size, lower farrowing rate, lower average daily gain, increased feed conversion, increased cost of medications and vaccinations, increased variation, decreased number of full value market hogs and higher mortality rates.

Loula described the creation of a North American PRRS Eradication Task Force that was initiated at the AASV board of directors meeting in Kansas City in 2006.  The Task Force’s goal is the complete eradication of PRRS.  Members, Loula said, have been starting local task forces in their regions bringing together producers, production systems, vets, industry partners and researchers to eliminate the disease region by region.  He reported that such task forces have already been established in Ontario, North Carolina and Minnesota. Three counties in Minnesota have eradicated PRRS in their area.

“The first step is to map out where the pigs and the viruses are so that we can track where they are going,” Loula said. He discussed some current methods of eliminating the disease in specific herds.  One way is to depopulate and then repopulate the site.  By moving the entire herd out of the barn, the producer is able to clean and disinfect the entire site. The herd is brought back in after everything has dried and the process takes about a week.  Follow-up studies, Loula reported, show that 49% of farms are still clear after 120 weeks and 39% after 150 weeks.

Herd closure is another method of controlling or eliminating PRRS by stopping the introduction of replacement animals to the sow herd for an extended period of time.  Those farms that have kept out replacement sows for more than 200 days have generally been successful.  This method allows the herd to develop a strong immunity to the virus.  New sows can be brought in 30 days after the last clinical signs of the disease.

Producers can also try a direct virus exposure using serum. Of more than 150,000 sows thus treated, Loula said, there were only two bad experiences.  A test and removal approach, Loula noted, is not in common use and works best alongside a second type of stabilization program.

Loula spoke of biosecurity measures intended to keep PRRS at bay in the first place.  He suggested filters to keep insects out of the barns and having visitors remove their shoes.

He also noted that vaccines are also available for some strains.  “Hog producers need to become knowledgeable about epidemiology, sanitation and biosecurity,” Loula said.  “That will benefit you long after the herd is free of the disease.”