A big step in preventing transmission of foreign animal diseases, or FADs, is to reduce virus-survival rates in imported feed ingredients, says Scott Dee, DVM, PhD, director of research, Pipestone Veterinary Service (PVS).
“We’ve learned that certain ingredients such as soybean meal, lysine, choline and vitamin D support certain viruses for a very long time,” Dee said.
Using 12 viruses or virus surrogates, investigators used simulations of feed-ingredient shipments from Beijing to Des Moines and Warsaw, Poland, to Des Moines.
Some of the viruses that survived well in these ingredients include foot-and-mouth disease, African swine fever, porcine reproductive and respiratory syndrome (PRRS) and porcine circovirus (PCV).
“The more we dig, the more we find,” Dee explained. “You remember when PCV roared across North America and raised havoc. PCV actually lives in quite a few of these ingredients. I wonder if that’s how the virus moved so quickly across North America.
“PRRS was a bit of a surprise because we didn’t think it would live in feed, but it does,” he continued. “So, maybe there’s not just a transboundary aspect, but a domestic aspect, too. This is how pathogens are moving from farm to farm, and potentially from country to country.”
Mitigants added to feed
Dee and his team are testing the use of mitigants (chemical treatments) to reduce survivability of viruses in feed. They selected 10 different mitigants to run through their simulated model testing to see if the viruses survive.
“We’re just starting to understand that no mitigant is perfect, but some are better than others,” Dee said. “If we can drive that challenge dose down, it becomes a lot easier to manage at the farm level.”
The mitigants they chose for this study are safe for use in pigs and human food. Dee said the products were either already approved by the FDA or are going to be approved.
Another possible option to reduce virus survival in feed is storing the feed until the virus decays enough to reduce its viral load. “How long would it take for this viral load to get down to where it is no longer an issue?” he questioned.
Maybe it will take a combination of both methods. “Not only do we mitigate to reduce the viral load first, but then we store it for a period of time to continue the reduction process,” he added.
The viruses that didn’t survive in feed during the simulated testing were built differently from the viruses that did survive. They are called enveloped viruses and include influenza, hog cholera and classical swine fever.
“The viruses that survive the best are what we call non-enveloped viruses,” Dee said. “They don’t have a lipid outer membrane, and they’re much more stable outside the host. They can withstand heat, disinfection and drying much longer than the enveloped viruses.
“So a viral structure is a component of this, as well as the ingredient characteristic, to make this high-risk combination,” he added.