Scott Dee, DVM, PhD, with the Swine Disease Eradication Center (SDEC) at the University of Minnesota (UMN), is optimistic when it comes to future control of PRRS. Porcine Respiratory and Reproductive Syndrome (PRRS) is estimated to cost producers from $5 to $7 per pig in the face of an outbreak, but over the last 2-3 years new tools have become available to aid producers and veterinarians in tracking, controlling and eventually eradicating this disease from the U.S. swine population. Initial results are very encouraging, notes Dee, in reference to new diagnostics, biosecurity measures and area control tactics. He discussed six advancements at a press conference during the 2009 World Pork Expo held earlier this month.
Oral Fluid Sampling
“This is an old idea that came from HIV surveillance in humans, and now it’s being applied to swine populations,” says Dee. The beauty is in the ease and simplicity of this technique, he explains. “Scientist Jeff Zimmerman and his graduate assistant, John Prickett, hung cotton ropes in pens where pigs were housed. Since pigs are naturally curious, they’ll chew on the ropes, from which saliva is obtained for testing. Pathogens validated through this method were PRRS virus, PCV-2, Swine Influenza virus, and Mycoplasma hyopneumoniae.
“It’s a great way to get a lot of barns tested while minimizing the labor and cost,” notes Dee. “This is the future when it comes to sampling large populations, especially in animal intensive areas and particularly when used for surveillance.”
Air Filtration
Researchers at the University of Minnesota have proven the PRRS virus can be transmitted via the airborne route out as far as 4.7 km. “There’s no question anymore about the risk of airborne spread – it’s black and white,” states Dee, “and I believe these viruses can travel much further. Based on our data, air filtration is the only thing I’ve seen that can truly prevent the virus from entering into and infecting swine populations.”
Dee has been using a production region model to test air filtration for three years, and has shown that pigs can be protected from PRRS and Mycoplasma. “It’s a ‘proof-of-concept’ model,” he notes. “It’s costly, so we’re looking at alternative methods of filtration so producers have options based on budget, location and level of risk.”
He is presently working with the Pipestone Veterinary Clinic, the Swine Vet Center and the Fairmont Veterinary Clinic to assess the efficacy of this technology in large sow units in high-dense regions. “It’s a work in progress, but the initial results are very optimistic. It’s the first thing I’ve seen in 20 years that has the potential to help us consistently produce non-infected weaned pigs,” notes Dee.
Modified Live Vaccines
Repeated application of a modified-live vaccine (in this case, BIVI’s PRRS MLV) stopped shedding from infected to non-infected pigs, states Dee. “We were looking at virus transmission from pig-to-pig, and wondered about vaccinating these pigs to minimize shedding in an infected population.
“We found that application of a modified live vaccine (MLV) to an infected population prevented shedding from infected pigs to those that were not,” he continues. While the vaccine didn’t clear the virus from an infected model, it did reduce transmission of PRRS virus and improve clinical response to infections and overall pig performance in the face of disease challenge. “The vaccine is an established product but now there’s a new way of using it,” adds Dee.
Risk Assessment Tools
The “Production Animal Disease Risk Assessment Program” (PADRAP) is a computer-based tool to measure and monitor risk factors, both internal and external, notes Dee. This tool was a gift from Boehringer Ingelheim Vetmedica, Inc. to the American Association of Swine Veterinarians in 2006, and requires training through that organization. Dee says a grow-finish risk assessment tool will be available soon. To date, over 1,474 risk assessments have been completed, and more than 904 sites are enrolled.
“We can determine what risk a particular farm has to other farms, and we can apply biosecurity measures and see if these protocols actually pay for themselves. The assessment also aids in decision-making regarding herd/regional elimination plans,” says Dee.
A PRRS biosecurity manual has been developed at the SDEC as well, thanks to funding from the AASV foundation. Dee points out that this is the first attempt to put all this information in one document. “We’ve tried to make it applicable, and it will be updated over time as we get new information,” he says.
Geographic Information Systems
Thanks to Peter Davies at the UMN, we now have software that can help producers assess, monitor and manage the PRRS status within a region. The system provides a picture of the area to facilitate decision making and an analysis of animal flow within that region.
“Extensive mapping and modeling of PRRS status and movement now allow us to more accurately predict and track PRRS spread in a region with greater accuracy based on pig movement, flows, transportation and delivery 
networks, biosecurity and other patterns,” explains Dee.
Area Programs
Area programs could very well be the first step in a successful disease eradication program, as exhibited in Stevens County, Minnesota. Dee says the work of Bob Morrison from the UMN and producers from Stevens County has demonstrated that producers could work together to control and eventually eradicate this disease. Stevens County (west-central Minnesota) was selected as a potential area, because it’s primarily a seedstock-producing area and not a lot of pigs enter the county. Many county producers who raise seedstock understand the value of diagnostics and the importance of disease eradication, so the proper mindset was already in place. There is a website where producers can log in and see their farm and where outbreaks are occurring. Morrison is expanding this project to surrounding counties in west-central Minnesota, with the hope of developing a PRRS-free area.
An Optimistic Outlook
PRRS control, and perhaps eradication, can become a reality, asserts Dee. In the Stevens County project, producers were talking to one another and working together for a common goal. Hence, Dee is optimistic about the future.
“Today more than ever before, producers can take a holistic, systematic approach to managing PRRS with greater success. Our improved understanding of the dynamics of the virus, transmission, infection, diagnosis and monitoring, and vaccination protocols have helped us provide producers with highly effective tools to turn the tide on PRRS infections.”
When he was president of the AASV in 2006, Dr. Dee, the executive committee, and the Board of Directors wrote this position statement: “Eradication of PRRS from the North American pig population is the long-term goal.”
The veterinarians have drawn “a line in the sand,” stating that we cannot live with this disease long-term. “Let’s no longer go on the defensive – let’s go on the offense and show how we can, with science and by working together, eradicate this disease,” he states.
Editor’s Note: This commentary is sponsored by Boehringer Ingelheim Vetmedica, Inc. and was derived from a presentation by Dr. Dee at the 2009 World Pork Expo and supporting material. For more information, go to www.bivi.com
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