Are we winning the battle with porcine reproductive and respiratory syndrome (PRRS)? Many would say we aren’t when you look at the data. But Scott Dee, DVM, argues the pork industry is winning in his mind.
“We know how to win. We have the formula, the knowledge and the tools to win. Now we just have to go get it done,” he said during a panel discussion titled “PRRS in the U.S. Industry: Why do we continue to battle with this well-known virus?” at the 2024 Allen D. Leman Swine Conference.
Dee was just starting out as a practicing veterinarian in Morris, Minn., when the “mystery disease” devastated the U.S. pork industry. He’ll never forget the day he walked into a barn and heard a noise that haunts him to this day. Silence.
“It was too quiet. The typical noise from clanging feeders and squealing pigs was gone. All I could hear were the sobs of a pork producer who had just lost his entire herd,” Dee recalls.
That’s when he began his battle against PRRS, a battle that he’s kept fighting ever since. He left his practice in 1999 to join the faculty of the University of Minnesota College of Veterinary Medicine swine group where he continued to research this frustrating disease.
“Over the years, I went through step by step by step, and identified these routes of transmission, proved them experimentally, and then developed biosecurity protocols for each route that validated scientifically,” Dee explains.
Let’s Put it to Test
Then he went to Pipestone, one of the largest pork producers in the U.S., to continue his research and see if he could take this information to develop an evidence-based biosecurity program to see if pork producers could prevent reinfection and eliminate the virus.
“We came up with what we call the four pillars of next-generation biosecurity (direct routes, fomite-based routes, aerosol and feed) at Pipestone,” Dee says. “We put it into our system and tested it over time to see if it really worked.”
The project kicked off in July 2021. Each farm in the Pipestone system was tasked with developing their own next-generation biosecurity plan for their farm.
“It was a system project where everybody was going to be part of the solution,” Dee says.
As part of the Morrison Swine Health Management Project, Pipestone had a measuring system in place to measure the number of new viruses in each farm every month, every year. Then, it was a matter of putting their plans to work and observing what would happen next.
“The numbers in year one were so good, with an 8% incidence of PRRS – crazy low. Historically, the company had incidence levels as high as 55%. PRRS had been a very prevalent organism. We started this research study with a history of having PRRS, like everybody else,” he says.
To make sure year one wasn’t a fluke, they ran the study again. The results were similar. After the year one and year two analysis, they noticed there were two cohorts within the data set – one was Next-Generation Biosecurity (NGB) complete where the farms were filtered and met all four pillars of biosecurity protocols. However, about 25% of the system was NGB incomplete, meaning they did not have air filtration systems in the barns.
“They were either too old, didn’t have enough money at the time, or weren’t disciplined to carry out that process,” Dee says. “These two cohort groups ran in parallel, side by side, and we didn’t really know this until we started looking at the data. We realized if you’ve got the NGB complete program, your first incidence is statistically much lower than if you don’t have the whole program.”
The research team also saw a statistical difference in the key productivity indicators (KPIs) between those two cohorts. So, in year three, they evaluated KPIs in the breeding herds.
“Just like you’d expect, we discovered the less PRRS in your sow herd, the healthier the sow herd. You’re going to wean more pigs. And that’s what we saw. In fact, the NGB complete cohort produced over 190,000 additional wean pigs that came out of the complete cohort as compared to the incomplete cohort. The ability to use the entire program was really significant,” Dee says.
Over the three-year period, 75 farms with over 380,000 sows participated in this project. Dee says they saw the cumulative PRRS incidence hover around 8% over those three years in the NGB complete herds.
“We were able to take the PRRS incidence and keep it below 10% for three years in a row. To me, that’s the most striking take-home message from the entire project, to take a system of this size and test it for this long and come up with a single digit outcome,” Dee explains. “This is the first time I’ve seen anything like this saying, ‘If you do this, this is what you’re going to get. If you don’t do it this, you’re going to get less. You’re going to get more PRRS, and you’re going to be less productive.’”
It’s common sense, but for the first time, it was documented, he adds.
What Does it Mean?
Dee admits he has never seen PRRS has controlled as well as it was over the three years in this study, but he points out it wasn’t perfect.
“You saw we still had some infections. The majority were in the non-filtered group,” he says.
But on occasion, they would have a complete farm get infected during repopulation, when they had a lot of trucks, people and pigs moving back and forth. Some farms got infected after “an act of God,” where a tornado came and ripped the roof off the farrowing house.
“If we could have had everybody filtered, who knows how low that incidence level could have been? Still, I was overjoyed to see that for the entire three years, a company of that size could keep PRRS virus at that low level.”
For years, the paradigm has been, “You can eliminate the virus, but you can’t keep it out.”
“We can change that paradigm now. We can say, based on data, you can eliminate the virus, and you can also keep it out. It’s not 100%, but it’s a heck of a lot better than when we started. This really changes the game, as far as decision making at the individual herd, at the area, and potentially even the national level,” he says.
Do they still see PRRS in the Pipestone herd? Yes. But Dee says it doesn’t paralyze the whole organization.
“In the real world, no matter how hard you try, sometimes things go wrong. Some things are out of your control,” Dee says. “But overall, we know how PRRS spreads. We know how to prevent that spread, and we now can eliminate the virus, and keep out reinfection with over 90% success.”
This research was published in Animals and the Journal of the American Veterinary Medical Association.
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