Senecavirus, PED, and PRRS survived in vials of feed ingredients for 21 days in a transport trailer
By Jackie Clark
Researchers executed a real-world demonstration project to confirm laboratory models of swine virus survivability in feed. Scientists infected samples of feed ingredients with Senecavirus, porcine epidemic diarrhea (PED) and porcine reproductive and respiratory syndrome (PRRS) and placed them in transport trailers for 21 days. The trailers travelled for 107 hours and 6,000 miles.
“This specific project was a test to see if viruses can survive in different feed ingredients under actual transport conditions,” Dr. Paul Sundberg, executive director of Swine Health Information Center, told Farms.com.
“We had modelled the transport conditions previously. We had built environmentally controlled chambers so we could put the virus and the feed ingredient mixed together in the chamber and we could control the temperature, the time and the humidity,” he explained. Through this demonstration “we wanted to show that under these real-world conditions of transport, that our model would hold with the survivability of viruses in different feed ingredients.”
In biosecure lab facilities, researchers have tested many viruses, including African swine fever, to better understand survivability in feed. When actual foreign animal diseases cannot be used, scientists use surrogates, such as Senecavirus as a surrogate for foot-and-mouth disease.
“The initial research used a variety of different viruses to model, especially the survivability of foreign animal diseases,” Sundberg said. For the demonstration, researchers used “PRRS, PED and Senecavirus, because those are production diseases endemic in the U.S. and we knew that there wasn’t going to be any risk of escape and infection.”
Scientists tested soybean meal (conventional and organic), lysine, choline and vitamin A. At the end of the experiment, researchers detected all three viruses in the soy ingredients, and Senecavirus was present in all five feed ingredients.
The outcome of the demonstration matched what scientists were expecting from their laboratory results.
“The results showed that there was survival of different viruses, especially in the high-protein ingredients like soybean meal,” Sundberg explained.
Soybean meal “seemed to protect the virus more than anything else,” he added. “Over the time period of the experiment, the viruses even died in the growth medium … but in the soybean meal they survived very well. That implies that there is something in that soybean meal matrix that is protecting the virus, rather than just letting it grow.”
The limitations of a real-world demonstration may not allow for direct extrapolation of the results, however, it served an important purpose.
“The important outcome or bottom line was that there were no surprises. ... It validated and gave us confidence in that model,” Sundberg explained. That means in the lab “the data that we see, even with the foreign animal diseases, is most probably accurate. … It showed that the experimental model is valid.”
This work is part of ongoing important efforts to assess risk of foreign animal diseases.
“The objective of all of this is to provide the regulatory officials in the U.S., the USDA (United States Department of Agriculture) and the FDA (Food and Drug Administration), with the data necessary for them to be able to assess risk from importation of feedstuffs, and also assess risk of transmission of viruses around the country once they get into the country,” Sundberg said.
“We recognize that there are limitations of this demonstration project,” he added. The researchers infected small samples, only 30-gram vials of feed ingredients, to ensure they could test the whole sample for live virus at the end point, and prevent false negatives.
“I think the next step … is to inoculate larger volumes of feed ingredients and do the same thing with them,” said Sundberg. “We don’t expect (the results) to be (different) but we think that if we do that, certainly it will add to our data that will add to our ability to assess risk.”
The risk assessment is helping to determine “important pathways of entry and movement” for swine viruses, he said.
Researchers conducted this demonstration as a partnership between the Swine Health Information Center and Pipestone Applied Research.
National Pork Board and the Pork Checkoff, Des Moines, Iowa photo