Can porcine reproductive and respiratory syndrome (PRRS) virus be eradicated in the near future?

A panel of veterinary experts provided some insight into the answer to this question during a PRRS roundtable discussion last fall. The Swine Practitioner roundtable in St. Paul, Minn., was sponsored by PIC.

Roundtable participants included: Butch Baker, a swine veterinarian and director of health assurance for Premium Standard Farms; Scott Dee, DVM, PhD, a former Minnesota swine practitioner and internationally recognized PRRS expert now doing PRRS research and teaching at the University of Minnesota’s Swine Disease Eradication Center; James Lowe, swine veterinarian and director of health and production services, The Maschhoffs, Inc., Carlyle, Ill.; Max Rodibaugh, swine veterinarian with Swine Health Services, Frankfort, Ind.; and swine veterinarian Paul Yeske, with the Swine Vet Center, P.A., St. Peter, Minn. Carlos Pijoan, DVM, PhD, director of the Swine Disease Eradication Center, moderated the discussion.

Unacceptable costs
Most roundtable participants agreed that the PRRS situation continues to be complex and that the cost of PRRS to the industry is an unacceptable cost that needs to be eliminated or at least reduced significantly.

They also agreed that there continues to be a lack of scientific information about PRRS virus immunology, among other things, that will make national PRRS eradication efforts challenging at the least.

Nonetheless, “I’m optimistic,” says Baker, with Premium Standard Farms. “We’re eliminating PRRS from a number of herds and pods,” he says. “We’ve had some setbacks, but overall, we’ve met with success.

“I’m willing to take what I know right now and attempt PRRS eradication in an area, region or farm. We’re currently doing it. If the industry needs an example, I hope we’re the one. We have our doubts and our financial managers have their doubts. Every time we have a failure, it’s a struggle to go back to the plate, but at this point we have a commitment to eradicate where it appears feasible.”

Baker adds that in his company’s North Carolina production system, “where we are very scattered and among many other local producers, the virus appears most stable. They see the fewest problems, and the breaks don’t seem as bad. It seems that perhaps the virus is becoming more species-adapted in that state. I believe that other integrators and large producers in the area see the same thing. In our isolated systems we’re our own worst enemy and we have the most problems with the virus. I don’t know why that is.”

Dee also is optimistic about the ability to eventually eradicate PRRS from the North American swineherd, he says. “We do know how to successfully eradicate the disease from individual sites. We’re getting a better handle on the routes of transmission.”

One black hole
On the other hand, remarks Dee, “where I’m pessimistic is in our lack of understanding of the immune response. That’s a big black hole that needs to be explored. It appears to be a confusing issue and nobody knows what’s really going on.”

Dee says it continues to be very difficult to successfully control PRRS virus, “especially when multiple viruses are involved. Multiple viruses complicate the issue. They complicate gilt acclimatization and vaccination. I don’t think control is a long-term option. I think we have to get into eradication in an entire region as the only way to live with this disease long-term.”

The long-term answer to the PRRS problem is eradication, agrees Illinois swine veterinarian Lowe. “But I don’t think we (can) go to the government or back to our producers with some grand plan until we have a lot more information,” he says.

“How do we reduce shedding so eradication is more possible? What strategies work? How many farms need to be involved? How big of an area do we need to include? What are the transportation risks? What are the methods of transmission? We need a lot more hard science so we can put a program together that has a probability of success.

“Because of the state of the industry today and the attitude of the producers, which is not very positive about PRRS, a program is going to involve a lot of learning and experimenting.”

Minnesota swine veterinarian Yeske also agrees that eventual eradication of PRRS should be the goal of the pork industry. “When we see individual herds where we’ve had eradication and we see the improved performance and production afterwards, that’s the carrot that keeps us looking.”

Role of geography
Yeske says that geography is one of the major players in the PRRS-virus situation. “If the herds are in an area of less pig density, we seem to be more successful. If we’re going to control these pig-dense areas and be able to operate, we have to understand immune response.”

Dee believes that PRRS eradication should be attempted first on a regional basis. “You might have a part of a county or you might have a state or you might have a specific segment of geography that would be considered a region,” he says.

In order to be successful, a regional eradication program would require “a group of cooperative pork producers in large enough numbers that will want to work together to clean the virus out of a large geographical region,” Dee explains.

Baker agrees that cooperation will need to be a prerequisite in order for PRRS eradication to be successful. He cites North Carolina as an example. “There’s a move going on there now through the veterinary school at North Carolina State University. They’re trying to get some of the larger producers together to at least discuss the potential for PRRS elimination. If we’re going to do anything, it will need to be a cooperative effort with our neighbors.

“I think regional eradication programs should be attempted. I think we should get on with it. A lot of money has been spent on PRRS study – probably more than all other swine diseases combined. We’re still not much ahead of where we were in the early ’90s when the thing spread through the industry.

“But we do know a lot more now than we did then. We’re finally getting the tools we need to eliminate the virus. I feel strongly that we need to move as fast as we can to area-eradication strategies. The industry will either do it or there will be components of that industry that will do it and have a competitive advantage.”   

           

Carlos Pijoan, a swine veterinary researcher and director of the University of Minnesota Swine Disease Eradication Center, was the moderator of the PRRS roundtable.

Indiana swine veterinarian Max Rodibaugh says he wonders whether a voluntary PRRS eradication program could work, as opposed to a regulatory program.

Lack of understanding of the pig’s immune response to PRRS virus is “big black hole that needs to be explored,” according to Scott Dee, University of Minnesota researcher.

The long-term answer to the PRRS problem has to be eradication, believes Illinois swine veterinarian James Lowe.

Minnesota swine veterinarian Paul Yeske says that geographic location is one of the major players in the effect of PRRS-virus on swine production systems.

Swine veterinarian Butch Baker says that Premium Standard Farms has been able to eliminate PRRS from pork production systems.

Editor’s note: This is the final article in a five-part series.

University of Minnesota to lead major PRRS research push

The U.S. Department of Agriculture has awarded the University of Minnesota College of Veterinary Medicine $4.4 million over four years to develop ways to reduce the impact of PRRS virus in swine herds. For the first time in its history, USDA consolidated smaller grants into one major national research program and the University of Minnesota was chosen to lead this project.

Some of the crucial elements researchers need to better understand are how PRRS arrives on a farm, how it spreads among pigs and how pigs resist infection. Researchers also need to develop better diagnostic tools to track the PRRS virus and to measure the immunity of the herd. Once these elements are in place, researchers can begin evaluating disease elimination strategies.

“PRRS is, by far, the most significant disease affecting swine,” said Michael Murtaugh, PhD, principal investigator and professor at the College of Veterinary Medicine. “We are working with the swine producers, veterinarians and allied industries to maximize the resources available to solve this problem and reach our ultimate goal – eliminating PRRS regionally, if not nationally.”

Eleven faculty members from the University of Minnesota College of Veterinary Medicine and College of Agriculture, Food, and Environmental Sciences join 57 other researchers from 20 different academic institutions collaborating on the PRRS research project. Additionally, the project will be supported by other industry representatives and the National Pork Board, making it one of the largest animal research projects in the nation.

The project goals include research designed to find solutions to the following areas of need:

  • Understanding PRRS biosecurity within herds.
  • Understanding the mechanisms of viral spread among herds.
  • Addressing the lack of efficient farm diagnostics.
  • Addressing the lack of adequate eradication protocols.

It is hoped that this major research effort will ultimately \include the following outcomes:

  • Methods to prevent establishment or to eliminate PRRS on farms.
  • Identification of factors involved in the transmission of PRRS among farms.
  • New farm diagnostic tools to detect infection, to identify genetic variants and to identify vaccine strains.
  • Regional eradication protocols.

Should PRRS eradication programs be voluntary or mandated?

When the pork industry progresses toward the development of PRRS eradication programs, should these programs be strictly voluntary or should they be mandated and regulated by the government?

Indiana swine veterinarian Max Rodibaugh says he has some concerns that not everyone would participate in a strictly voluntary program. “I still have concern about getting everybody on board without some regulatory involvement,” he says. “There are examples already with PRRS where small herds have infected large systems. That small-herd owner may not be interested in cooperation. Due to funding limitations and the nature of the virus, a PRRS program would likely be considerably different from the pseudorabies eradication program.”

Butch Baker, a swine veterinarian with Premium Standard Farms, believes that due to the consolidation of the pork industry, a voluntary program could be feasible. “We’ve seen enough consolidation where only a few players need to make the decision,” says Baker. “I do think that producers would band together and make the effort.”