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Porcine epidemic diarrhea virus continues to spread

By Lisa Young
lyoung@agrinews.com

Date Modified: 02/24/2014 11:24 PM

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The colder-than-normal winter has aided the spread of porcine epidemic diarrhea virus. Most recently, it has migrated to operations in central Minnesota, said David Preisler, executive director for the Minnesota Pork Board.

"That's disappointing," Preisler said. "It's a tough virus. This winter isn't doing us any favors."

One particular challenge is that the cold has made it difficult to get trucks and trailers clean and completely dry. Warm weather will help with that, but it won't stop the spread of PEDV, which is fairly heat tolerant.

Several hundred farms across the state have contracted PEDV so far, with the largest uptick coming in the past two months. While the virus' continued spread is frustrating, advancements lend some hope, Preisler said.

Recent PEDV survivability research should help producers' biosecurity decision making. The new surveillance test from the University of Minnesota will help in tracking which swine have developed immunity to PEDV. Several companies are also working on vaccines.

Ongoing research continues around immunity and how long it may last, as well as feeding risks, Preisler said.

One surprising side effect from all the biosecurity measures producers have put in place because of PEDV is that porcine reproductive and respiratory syndrome incidence has dropped.

Preisler recommends producers and farm visitors continue to follow National Pork Board-recommended biosecurity measures, tailoring them to their own operations as much as possible.

With significant piglet loss, full market ramifications remain to be seen. Preisler expects pork industry stakeholders will have a better idea of what the affect may be within the next six months. However, he expects early indicators out of North Carolina by the end of March since the pork stronghold was hit early and hit hard with the virus.

The futures market already is showing the market likely will be on the higher end of historical norms.

More than one strain?

Iowa State University's Veterinary Diagnostic Laboratory found there is more than one strain of PEDV active in this outbreak in the United States, ISU VDL said in a recent press release.

The labhas been sequencing PEDV DNA for clients to determine the genetic relatedness and molecular epidemiology of PEDV in U.S. swine. In sequencing 15 cases Jan. 24 to Jan. 29, the lab found10 were similar to each other and the PEDV strains identified in U.S. swine since April 2013.

However, five cases were only 93.9 percent to 94.6 percent related to previously identified strains but were 99.6 percent to 100 percent related to each other. These five had some deletions and insertions compared to PEDV strains previously identified in the United States.

Based on available data, it appears unlikely these five strains are mutants evolved from PEDV previously identified in U.S. swine. ISU VDL staff are in the process of completing the entire genome sequences for the new PEDVs, which will help determine the origin of the viruses.

PEDV is a survivor

New University of Minnesota research shows minuscule amounts of PEDV can survive for extended periods in multiple mediums. The findings double down the importance of extensive cleaning for anyone attempting to eliminate the virus.

Sagar Goyal has been assessing PEDV survivability since summer 2013. His most recent results looked at PEDV survivability in fresh feces, manure slurry, drinking and recycled water and feed.

Despite assessing various temperatures and humidity levels, PEDV can last a week in fresh feces.

"If feces from infected pigs are present in the barn, the virus can survive for seven days or more," Goyal said in a press release on his work from the National Pork Board.

While PEDV survived for 14 days at room temperature in manure slurry, cold temperatures boosted the virus's lifespan. At 39 F and minus 4 F PEDV was able to survive at least 28 days. It may survive longer than that, but Goyal's study didn't go beyond that timeframe.

PEDV could survive in drinking and recycled water for at least seven days and up to 13 days, Goyal found. The next step is determining if water chlorination can help.

While dry ground feed only allowed PEDV to survive for seven days, wet ground feed provided a more hospitable environment, allowing PEDV to survive at least 28 days. Again, the duration could be longer, but Goyal's study ended. Storing infected feed at room temperature for two weeks should kill the virus.

"However, we don't know if colder temperatures enhance survival," Goyal said. "My advice to producers is to pay attention to the virus survivability results. If it survived one week in experimental conditions, I would double the time just to be on the safe side."

Goyal's findings indicate biosecurity and cleanliness must remain a top priority, said Butch Baker, a swine researcher at Iowa State University.

"There are clean barns and then there are barns that are said to be clean, Baker said in the release. "They are not the same. You have to empty and clean out facilities and that includes waterers and feeders. You have to get the biofilms out of there and it does take a considerable effort."

Searching for a vaccine

Animal health company Zoetis is partnering with Iowa State University in the quest for a PEDV vaccine, the two organizations said in a recent press release.

"We look forward to working with the top researchers at Iowa State University to share knowledge and expertise as we make every effort, together, to help veterinarians and producers fight PEDV," said Gloaria Basse, Zoetis U.S. Pork Business Unity vice president.

"We know how devastating this virus has been to the swine industry," said Jianqiang Zhang, ISU Veterinary Diagnostic Laboratory assistant professor. "We are eager to work with Zoetis and advance the research we've begun to find a solution."