Iowa State study: Swine virus cost pork producers $1.2B a year

As America’s top hog producer, Iowa generated $10.9 billion in cash receipts in 2022 — but it could have made more if not for the persistence of porcine reproductive and respiratory syndrome, according to new Iowa State University research.

That viral disease, known by the acronym PRRS, cost the U.S. pork industry about $1.2 billion in lost production annually from 2016 to 2020 — amounting to an estimated $4.8 billion over that span, according to the ISU assessment.

And the problem is getting worse as the annual industrywide hit from that four-year period was 81 percent higher than a decade earlier, according to a 2012 study that revealed annual estimated PRRS losses from 2006 to 2010 reached $664 million.

“After 40 years of experience fighting this virus, veterinarians and producers are still losing the battle against PRRS,” according to ISU professor Derald Holtkamp, who led the original 2012 study and the more recent update.

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Part of the challenge with controlling the disease is its ability to evolve and evade vaccines, said Holtkamp, who’s been a professor of swine production medicine at ISU for nearly 20 years after serving for a period as a veterinarian and industry consultant.

“As a veterinarian and a researcher, several times in my career I thought, I think we've got this figured out, I think we know how to control this virus now,” Holtkamp said. “And within anywhere from two to five years, it proves us wrong. It makes us look silly again.”

It’s an evolutionary “intelligent” virus, he told The Gazette. “From an evolutionary standpoint, it is able to outsmart us at every turn,” he said.

‘How many pigs either die or survive’

PRRS first was described in American swine herds in Iowa, North Carolina and Minnesota in 1987-88 — causing reproductive impairment or failure in breeding animals and respiratory illness in pigs of any age, according to ISU.

Characterizing the virus as the "most economically important disease now affecting producers,“ Holtkamp — who has a master’s degree in agricultural economics and a doctorate in veterinary medicine — said ”cost of disease“ studies are imperative for informing industry changes and decision-making.

“It’s foundational data for big producers,” he said of his research, which relied on weekly herd disease data collected through a University of Minnesota swine health reporting program and productivity data collected from pork producers.

Productivity, Holtkamp said, is measured by how many litters producers have annually, how many pigs are born alive in each litter and how many are weaned each year.

“Ultimately, the one that's most important in a sow herd is how many pigs we're weaned in total,” he said.

In the growing stage of a pig’s life cycle, Holtkamp said, productivity is measured by rate of growth — average daily gain — and how efficiently pigs convert feed, measured in pounds of feed required to get one pound of pig.

“And then probably the most important measure would be piglet mortality,” he said. “How many pigs either die or survive.”

Once his team had estimates of differences between affected and unaffected herds, they put an economic value on it — including how much meat could have gone to market that didn’t.

And they found 80 percent of the $536 million increase in annual PRRS losses between the first study and the more recent analysis — about $428 million — could be tied to the amount of animals affected and the impact on their productivity.

“The sharp increase in economic damage caused by PRRS isn’t driven by changes in market prices, production cost or the size of the U.S. pig inventory,” according to an ISU summary of the research. “Those factors only account for about $108 million of the $536 million increase in annual losses.”

‘Find those risks’

While the financial hit was surprising to Holtkamp, he said it wasn’t to pork industry veterinarians. “Without fail they say, ‘Nope, that seems right,’” he said.

Pointing again to past attempts to stop the highly-adaptable virus — which so far have failed — Holtkamp said the more recent study found a disproportionate impact on herds of growing pigs, as opposed to breeding herds.

Growing herds — also known as market hogs raised to grow quickly — accounted for 55 percent of lost production in the first study and 68 percent in the follow-up, which Holtkamp attributed to new virus variants and changes in sow immunization methods.

“I've been battling this virus really my entire career, both as a researcher and a veterinarian — and many veterinarians that I know have been in a same boat,” he said. “Many of us have not known what it’s like to practice or try to raise pigs in a time when we didn't have PRRS virus.”

What this study highlights, Holtkamp said, is that spending the time and energy to figure out a solution would be worth it.

“Not only are we not improving or getting better at controlling the virus, we're actually probably going the wrong way here,” he said. “It's the type of virus that has the ability to change very rapidly … it can even exchange genetic material with other PRRS viruses.”

Heightened biosecurity, he said, is essential to reversing the impact on an industry that has seen increased consolidation and growth — making facilities more interconnected and at risk for exposure. Holtkamp urged producers to continue identifying their biggest biosecurity gaps and best prevention methods.

“It can be complicated, but it’s worth it to spend that time to find those risks.”

Comments: (319) 339-3158; vanessa.miller@thegazette.com