Pig virus may spread by wind

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Researchers in Minnesota found indications a virus that sickened and killed U.S. pigs starting in 2013 could be spread among farms through aerosols carried by wind.

But, by mid-January, the researchers had not found proof that the virus responsible for porcine epidemic diarrhea can spread by airborne particles.

(Photo by Peggy Greb/Courtesy of USDA ARS)

Dr. Dane Goede, a graduate student at the University of Minnesota who is leading the seven-person research team investigating the lateral spread of the PED virus, said PCR assays found RNA from the virus in 11 of 64 wind samples that were taken in the Oklahoma Panhandle and southern Kansas at distances ranging from 20 feet to 10 miles from barns with known infections. But bioassays conducted by use of those field samples did not produce infections in pigs.

“We think that these particular samples just were not viable, and there are a couple of reasons why that would be,” Dr. Goede said. “First of all, I was collecting these samples in the hot Oklahoma sun.

“If they’re 10 miles away, then it has 10 miles to be exposed to UV rays—to desiccating conditions.”

Dr. Goede explained that the time of day and season could affect virus viability.

The study also showed a correlation among wind patterns and the direction of spread of the virus to naive farms, he said.

The virus was first discovered in the U.S. in April 2013, and it has since spread to at least 23 states, according to information from the American Association of Swine Veterinarians. The virus is believed to have originated from China’s Anhui province, according to an article published in October 2013 in mBio, an online journal from the American Society for Microbiology.

Dr. Tom Burkgren, executive director of the AASV, said that, while the study results are preliminary, the findings are concerning because of the potential added difficulty in containing the disease on a farm. The AASV published a description of the preliminary study results in a newsletter and on the organization’s website.

Dr. Goede said the study on windborne PED virus was started following reports that infections were spreading in the region with unexplained speed, and the direction of spread was similar to wind patterns. He said it was shocking to find the virus in air samples, “especially three miles, five miles, 10 miles away from a farm.”

Related JAVMA content:

Viral disease affects U.S. pigs (July 1, 2013)