Newly published research shows the pig virus that swept through the United States beginning in 2013 and killed more than six million piglets could survive a trip around the world, if it catches the right ride.
The porcine epidemic diarrhea (PED) virus found in this country closely matched the version circulating in China, fueling speculation that the virus came from there. To confirm that, scientists want to understand exactly how it made the trip, but that has proved difficult. Last fall, the U.S. Department of Agriculture put forth the idea in its investigation of the root causes of PED that fabric shipping totes used to send bulk materials around the world could have harbored the virus. (PDF)
Now, researcher Scott Dee of Pipestone Veterinary Services says he has demonstrated in the lab that the virus needs a host it can interact with, which will support it. In an otherwise empty container, Dee found the virus did not survive.
"It's not the container that these things are traveling in," Dee said, "it's potentially the ingredient or the contents of the container that allows the virus to survive."
Dee found that conventional soybean meal, organic soybean meal, lysine hydrochloride, Vitamin D, and choline chloride all created a PED-friendly environment, while in the other ingredients the virus died. Dee's work was published Saturday in BMC Veterinary Research.
"In the presence of certain feed ingredients, under conditions that simulate a trans-Pacific journey," Dee said, "contaminated feed ingredients, if they're the right ones, could have certainly supported virus survival throughout this entire 37 day trip." (Read more about his experiment here.)
USDA's Brian McCluskey, executive director for science, technology and analysis services, said Dee's work supports the government's findings on possible ways the virus could have entered the country, but that it has not yet convinced the agency of PED's root cause.
"It is evident from [Dee's] research and some of ours that the PED virus can survive in feedstuffs and the containers that deliver the feedstuffs for the time it takes to transit from Asia to the U.S.," McCluskey said in a statement. "This is still not conclusive evidence that PEDv arrived in the U.S. by one of these pathways."
Dee's study also tested two treatments and found that each of them could kill the PED virus if applied to a contaminated ingredient.
Dee said he hopes his findings will lead to more research on animal diseases that have not yet made the leap here from other continents, such as foot and mouth disease and African swine fever.
"There is a number of really bad agents we don't have," Dee said, "and I think this work that we did with PEDV will open some doors for a lot of investigations along those lines."
Dee also said the prospect of unwanted pathogens hitching a ride in feed ingredients could influence where hog producers source their ingredients.
"`Buy U.S.' might be a slogan that would come out of this," he said, but quickly added that his results are only a small-scale model. "So I don't think anyone's quite ready to do anything yet, except for discuss the data. And that's really what I want to do, is just raise awareness, open some minds and start some conversations."
This story was updated with additional information on Monday at 3:45 pm.