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Porcine epidemic diarrhea virus continues relentless spread

Pork producers across the country are continuing to grapple with a virus that’s killing their piglets. Experts estimate Porcine Epidemic Diarrhea (PED) virus has already killed about 1 million baby pigs and the disease shows no sign of abating.

Whether the deaths blamed on the virus will ultimately force a rise in consumer pork prices likely will not become clear until spring or summer when the lost piglets would have reached market age, because many other factors are in play, including lower feed prices than last year and the related ability to put more meat on the hogs that do reach the market.

A USDA report from the end of December shows the total U.S. swine herd at nearly 66 million animals, so the 1 million pigs that may have been lost to the disease last year is not a devastating figure, though it is still cause for ongoing concern.  

For now, though, farmers are hoping new vaccines will stop the rapid spread, because PED is resilient and squirrely. The disease first turned up in the U.S. last spring. Prior to that, it had been doing damage in parts of Europe and Asia, where efforts to quell it with vaccines have not been terribly successful. Hank Harris, founder of Harrisvaccines, an Ames, Iowa-based startup company currently working on PED vaccines, had followed developments in Asia.

“One of my former graduate students is from Thailand and he has been working on porcine epidemic diarrhea for the past two years,” said Harris, who is also on the animal science and veterinary medicine faculties at Iowa State University. “So we had been talking about developing a vaccine and sending it to Thailand.”

Then, extensive testing confirmed samples found in Iowa last April were not a different swine virus frequently found in the U.S. but were, in fact, PED.

“As soon as it occurred in the United States, that increased our interest significantly,” Harris said.

Other veterinary medicine companies in the United States have also been busy developing vaccines. Harris’ first vaccine for PED is now available with a veterinary prescription, and the company has applied for a license from USDA to market it more widely, which Harris expects to receive mid-year. But, Harris says, the current vaccine is not enough to protect all piglets in infected herds.

“It’s not giving 100 percent protection in those situations and so that’s why we have a generation two vaccine that we’re developing already,” Harris said.

Like Harris, Sabrina Swenson of the USDA’s National Veterinary Services Laboratory knew PED was out there and could come to this country.

“One of our roles is to try to anticipate potential things and to try and make sure we have diagnostics in place,” Swenson said, “and many years ago we had concern of the potential for PED to come into the United States.”

Since its arrival, PED has been spreading relentlessly. Think of a preschool classroom where the children must wash their hands several times a day. Even so, when one gets a cold, most others quickly succumb and they tend to get sicker than their parents and teachers. PED spreads fast within barns and from farm to farm, even when strict biosecurity measures—the hand washing of the livestock industry—are in place. That’s because it can survive in tiny bits of manure that travel on boots or trucks.

Adult pigs typically recover from the disease. But Rodney Baker, a professor of veterinary medicine at Iowa State University, says baby pigs do not.

“The pigs die from dehydration,” Baker said. “The baby pigs just cannot withstand losing all their body fluids as fast as they do.”

Once they reach about 10 weeks of age, Baker says, the piglets aren’t nearly as vulnerable.

“They develop diarrhea for a day or two and they don’t really appear all that sick,” he said. “Most of them continue to eat and drink and just have diarrhea and in three or four days they get over it.”

That means PED poses the biggest threat to the farms with sows and piglets. And, Baker says, the number of sick piglets is likely to grow.

“It’s easy to imagine that we could have lost a million pigs, and before the winter is over I wouldn’t be surprise if that impact would be maybe three, four times that,” Baker said.

The virus also likes the cold. Early results from a study funded by the National Pork Board show that killing this bug on a metal trailer may require heating it to 160 degrees Fahrenheit for 10 minutes.

Baker says smaller, independent producers—ones that have fewer hogs and minimal contact with other farms—are having the most success keeping the virus out. He says that’s because on larger operations there is more opportunity for trucks and people to move between barns. And because when they get infected more litters are lost.

The PED virus poses no threat to food safety or human health. Unless, of course, it eventually makes bacon unaffordable.

Amy Mayer is a reporter based in Ames