It’s impossible to mention the swine industry without discussing African swine fever (ASF), the epidemic sweeping eastern Asia that has U.S. producers worried that it’s only a matter of when, rather than if, the virus makes its way through the U.S. herd.
To discuss the challenges of tracking and containing African swine fever, South Dakota State University brought in Dr. Megan Niederwerder to give the keynote address at its annual Swine Day in Brookings Nov. 5.
Niederwerder is an assistant professor at Kansas State University and has been heading research into how African swine fever could be transmitted to the U.S. through feed imported from China and other southeast Asian countries. The reason Kansas State has begun looking into this, besides the obvious threat the disease presents, is that the U.S. saw similar transmission from porcine epidemic diarrhea virus (PEDV). Back in 2013, PEDV wiped out about 10% of the U.S. swine herd.
“After it was introduced, it spread rapidly throughout the country. Within two months, it was reported in every swine producing state in the U.S.,” Niederwerder said. “Now it’s an endemic disease we deal with on a day-to-day basis.”
PEDV, which isn’t nearly as severe as African swine fever, was found to be primarily introduced through pig feed. Researchers found that the disease in the U.S. found 99% similar to the virus found in China, and they learned the disease could easily survive the boat travel between the two nations.
After doing a study into PEDV, KSU researchers began to look at the posibility of African swine fever being transmitted to the U.S. via feed imports. They had three key questions: Can African swine fever (ASF) be transmitted through feed? Can the virus survive shipment from China? And what are the ways we can mitigate risk at home?
These three questions were quickly boiled down to just two. There is no doubt the virus can be transmitted by feed, Niederwerder said.
“When we think about all the risk factors for ASF, the question is always: how would that get to our pigs,” she said. “We know how that would happen with feed. That’s not a question at all for feed.”
Looking into the next part of the equation - how it would survive during transit – was done in part due to a technique developed at SDSU. Kansas State used chambers designed to simulate trans-Atlantic and trans-Pacific travel, and SDSU is to thank for those techniques.
The team at Kansas State studied many viruses during this test, but focused on African swine fever and classical swine fever.
“We found that (ASF) was very stable during its 30-day period,” she said.
Not only was it stable, but it survives more effectively in the feed, she said. The study looked at 12 host sites for the virus, ranging from conventional and organic feeds to sausage skins. Out of those, nine successfully harbored the virus through transit.
Classical swine fever survived in two of the sites, but researchers determined that African swine fever was the second most successful virus during travel, behind only foot and mouth disease surrogates.
Next, the study focused on just how much feed it would take for pigs to become infected with the virus. Using 80 piglets between seven and eight weeks old, researchers found that even with the smallest amounts of infection in feed, it wouldn’t take more than a week for every pig to become infected.
“Yes, pigs can get infected through liquid feed and plant-based feed,” she said. “If a contaminated batch of feed provides feed for three to five days, it’ll continue to infect that animal.”
Reducing the risk of contracting African swine fever in the first place boils down to either rejecting feed sourced from countries with African swine fever, or storing it for a period of time in heat treated, antiviral chambers, Niederwerder said. Kansas State has not been able to study storage time or temperatures to give recommendations there.
Niederwerder and her team have looked at the half-life of African swine fever and other viruses to determine how long it would take for the virus to die out. It will take more time to collect conclusive data, but she drew some observations from their travel-time study.
“During that first half of the trans-Atlantic model, we saw fairly rapid decay,” she said. “But in that second half, the reduced viral decay implied that there was stability over time. There is just something about the feed matrix that is promoting stability of the virus.”
During the question and answer period, Niederwerder was asked if Kansas State or others are looking to test feed at the port to make sure it’s contaminate free. She said that there is no such testing being done, to her knowledge.
“We’d like to get to the point where we can look at bulk feed ingredient diagnostic testing,” she said.