A new risk threatens the swine industry. Researchers have found that under experimental conditions, the right virus paired with the right feed ingredient could potentially survive a journey across the ocean and enter the U.S. feed supply.
When Porcine Epidemic Diarrhea virus (PEDV) erupted in the U.S. in 2013, the Pipestone System escaped the initial wrath of this devastating disease. But in early January 2014, several of the system’s farms became infected at approximately the same time.
As the Pipestone team began identifying points of similarity, they realized that feed outages had required the delivery of new feed to each of the farms that broke with PEDV. Within a few days, animals that consumed these feedstuffs were identified as the index cases of PED in each farm.
Could this disease have entered the U.S. through the feed supply?
“I was told in 2013 that there was no way the virus could live in feed,” says Scott Dee, DVM, Ph.D., Director of Research for Pipestone Veterinary Services. “I didn’t believe that.”
Armed with a few long paint rollers, Dee took swabs from inside each of the feed bins and confirmed PEDV was present in the bins that contained the most recent shipment of feed to each of those farms. He then fed it to pigs under experimental conditions at South Dakota State University (SDSU) and reproduced the disease, the first ever documented feed-based bioassay involving PEDV in the history of veterinary medicine. The findings were soon published in BMC Veterinary Research, a journal allowing open access to the information to everyone.
“After we had answered the “could it be feed” question, I’ll never forget sitting around our conference room discussing how it could have possibly entered the U.S.,” Dee says. “We hypothesized about the potential of a new risk factor: Could feed serve as a vehicle for the transboundary spread of the virus. We had unique insight, as our China team, Drs. Gordon Spronk, Luke Minion, and Cameron Schmitt had been dealing with PEDV in China long before it ever came to the U.S.”
Not long after this conversation, Spronk called Dee and together they visited his brother’s (Randy Spronk) feed mill right away.
“When I arrived, they showed me a bag of choline from China,” Dee says. “No one had really paid attention to this before. The production date on the bag was only two weeks earlier. No one could believe it made it over here that fast. Immediately, the light came on – maybe we were bringing PEDV in through regular shipments of contaminated ingredients.”
Immediately, Dee, along with Dr. Eric Nelson of SDSU went to work figuring out how to model the transboundary path from Beijing to Des Moines, Iowa.
To simulate the environmental conditions that cargo would encounter during this trip, Dee used an environmental chamber to reproduce temperature and humidity fluctuations on a daily basis. Nelson provided insight on how to spike samples of feed ingredients known to be imported from China with PEDV. They used representative transport times and environmental conditions and tested the samples at different points along the path to determine what viruses could survive the long journey.
The study grew and under the direction of Dr. Paul Sundberg, the Swine Health Information Center (SHIC) became involved. They expanded the testing across an additional 11 viruses, such as African Swine Fever Virus and Seneca Virus A, a surrogate for Foot and Mouth Disease virus. They worked with Dr. Diego Diel from SDSU and Dr. Megan Niederwerder from Kansas State University, to set up trans-Pacific and trans-Atlantic models and run the studies.
“Working with Diego and Megan, along with their respective teams, was the reason this project was so successful,” Dee says. “Pipestone had the idea, but the universities helped us bring it to fruition.”
Growing Body of Evidence
The results confirmed Dee’s previous finding on the survival of PEDV in feed, as well as the survival of several viral pathogens in multiple feed ingredients or feed products.
Under the conditions of the study, three specific conclusions were drawn:
- Viruses can survive in feed, but survival is variable and depends on specific properties of each virus.
- Certain feed ingredients or feed products present a better matrix for virus survival than others.
- A new risk factor for the domestic and transboundary spread of viruses had been identified.
Dee says with this new information, the industry needed a clear plan to deal with the risks.
“How do we introduce essential feed ingredients that are not produced in the U.S. from high risk countries?” Dee says. “In the vision of our CEO, Luke Minion, we needed to be responsible importers. Keeping Luke’s original thought in mind, I developed a science-based protocol that is focused on the safe entry of unique ingredients. It’s a concept we can all stand on and communicate with a clear voice.”
Dee says it provides a guideline when the need arises to bring in ingredients from high risk countries, while still making sure the recommendations are based on science.
Dee recently shared the Pipestone Responsible Imports vision and plan of attack at the Allen D. Leman Swine Conference.
“The multi-pronged approach involves the use of efficacious mitigants, calculated storage time, and a good dose of common sense,” he says. “The concept was well received across veterinary and producer groups. In addition, feed manufacturing companies are also trying to help. The feed industry sincerely wants to be as transparent and risk-adverse as it possibly can. I am so impressed with the response of the [American Feed Industry Association] – they are really stepping up.”
“We are in such a different place with ASFV than we were when PEDV hit,” Dee says. “We are not infected. We are all focused. We have data that we can use proactively.”
He encourages the industry to be vigilant: “We are at risk. As the African Swine Fever epidemic increases in China, the level of environmental contamination of a very stable virus increases, leading to contamination of other farms, meat and feed. If we keep doing business as usual, our risk increases. If we become responsible importers of essential feed ingredients, our risk decreases.
“That bag of choline was the turning point,” Dee adds. “You have to get out and see the real world or you will miss moments like these. If Gordon hadn’t taken me to Randy’s mill, then we wouldn’t know what we know today about this new risk in our industry.”
Editor’s Note: “Survival of viral pathogens in animal feed ingredients under transboundary shipping models” was published in PLOS ONE on March 20, 2018. This research was funded by the Swine Health Information Center, American Association of Swine Veterinarians Foundation, State of Kansas National Bio and Agro-Defense Facility Fund, SDSU Animal Disease Research and Diagnostic Laboratory, and the business unit of Pipestone Applied Research (Pipestone Holdings) provided salaries.