KANSAS CITY, MISSOURI, US — The United States has been dealing with a widespread outbreak of highly pathogenic avian influenza (bird flu) since 2022, but it has never reported a single case of African swine fever (ASF), which has ravaged pig herds in Asia and Europe in recent years.

First discovered in 1920 in sub-Saharan Africa, the largest ASF outbreak occurred in China in 2018, where an estimated 225 million pigs either died or were culled over a two-year period, causing a 25% reduction in the global pig population. Another large outbreak began in Europe in 2022 and is still impacting the continent today.

Speaking at the International Production and Processing Expo (IPPE) earlier this year, Jordan Gebhardt, assistant professor of swine production at Kansas State University, said the US Department of Agriculture (USDA) and industry officials are going to great lengths to keep the disease outside US borders.

It crept closer to US shores in 2021 when cases were reported in the Dominican Republic and Haiti.

“It’s on our doorstep in the Western Hemisphere and we have to be vigilant,” Gebhardt told attendees at the “What Keeps the Feed Industry Up at Night?” symposium sponsored by the American Feed Industry Association (AFIA).

The good news is that ASF causes no direct harm to humans, as it only infects pigs and other domestic and wild animals. Also, humans cannot contract the virus by consuming pork products from infected pigs.

But the economic impact of an outbreak has been significant in Asia and Europe and would be in the United States as well.

“The most significant economic implications would be related to trade,” he said. “Today, the US swine industry exports nearly 30% of the pork it produces. If it is detected here, those exports would shut down very rapidly or be greatly reduced.”

A recent analysis by Dr. Dermot Hayes at Iowa State University estimated an ASF outbreak in the United States would result in $15 billion in economic losses over a two-year timeframe and up to $50 billion over a 10-year period if it was not eradicated. Although the swine industry would be severely impacted, Gebhardt said allied industries including feed manufacturers also would be affected.

Preventive measures

Gebhardt discussed measures that the US government is taking to prevent ASF from entering the country and what feed mills can do to keep it from contaminating their products.

If ASF is detected in the United States, there will be no movement of pigs for 72 hours, according to the USDA Response Plan. 

“Beyond that there’s a lot of questions and uncertainties about what would happen,” Gebhardt said. “It would be at the discretion of state animal health officials in collaboration with the USDA.”

While most of the bulk feed ingredients used in US feed mills, such as corn and soybean meal, are produced domestically, much of the non-bulk ingredients, which are shipped in bags or one-tonne totes, come from regions or countries where ASF is present, Gebhardt said.

“Over the last decade, tests have been performed mimicking transportation conditions from countries that have ASF and ship to the US and the pathogen appears to remain viable throughout that journey,” he said.

As a precautionary measure, Gebhardt said extended holding times are recommended once feed ingredients arrive in the United States. 

Research also has been done to see what happens when ASF makes it inside a feed mill and into the feed supply chain. Kansas State University and a large feed manufacturer in Vietnam in 2019 collaborated on a project in which samples were taken inside a feed mill shortly after ASF was detected in that country.

Out of 2,328 samples taken from the feed supply chain only 17 contained ASF DNA, with positive samples coming from three contact surfaces inside the mill, four from non-feed contact surfaces, two from employee clothing, one from complete feed and seven from feed trucks, he said.

“One of the important takeaways is that the emphasis was placed on feed, feed ingredients, thermal processing, but what about everything else? What about people? What about trucks?” he asked. “One of the things that was most eye opening was that a little over 50% of the positive samples came from feed trucks or shoes and clothing of mill employees. The ingredients and feed are important to monitor but you have to think about other aspects as well.”

Once the trucks were identified as a problem, the mill changed its disinfectant procedures and no positive samples were detected from feed trucks after that, Gebhardt said.

“The vast majority of contamination actually occurred in truck cabs,” he noted. “They weren’t disinfecting the cab very well and drivers were unknowingly going in and out of infected farms and bringing it into the cab of the truck and then into the feed mill.”

SHIP program

The USDA has established the US Swine Health Improvement Program (SHIP), which emphasizes preparedness for ASF and Classical swine fever (CSF) in the form of prevention, response and recovery.

Gebhardt said more than 12,000 sites from 36 states were enrolled in the program as of December 2024, accounting for 76% of the US breeding herd and 65% of the pig herd. 

“It’s a relatively recent program but it’s seeing very good uptake from the industry,” he said.

As part of the program, a Feed Biosafety Working Group has been formed that is comprised of 35 representatives participating in the SHIP program, including veterinarians, nutritionists, feed ingredient suppliers, trade associations, allied industry and federal and state regulatory partners. 

“The program characterizes what processes and biosecurity standards are currently being implemented by swine producers,” Gebhardt said. “It is focused on non-bulk ingredients coming from countries affected by ASF or CSF. We wanted to know what’s being done in those cases.”

The goal is to create standardized practices for how ingredients would come into the United States, he said. Voluntary participants in the SHIP program were surveyed about their holding time for imported ingredients. About 57% said they required 30 days storage, 14% said 45 days, and 29% said 60 days, Gebhardt said.

When asked to define when the storage period begins, 40% said the clock starts ticking once the product arrives in the United States from a country affected by ASF. Another 40% said it began when the material entered the warehouse of the feed mill, while 20% said it began when it exits the port of the exporting country.

The survey also asked about temperature requirements during the quarantine of imported feed ingredients. A wide range of responses were given with about 22% having no requirement; 11% at above freezing; 11% ambient temperature; 11% at 60 degrees F; 22% at 70 degrees F; and 11% at 75 degrees F.

Overall, 45% reported no standardized holding conditions, 43% said they held the ingredients for 30 days with no set temperature, while only 12% held it for 30 days at a temperature of 68 degrees F or greater.

“This was all really good information that helped us quantify where we are today,” Gebhardt said. “The industry will have to make a decision about how they want to proceed in this area. I really think that’s one of the novel aspects of the US SHIP program. It gets all the relevant stakeholders to have a discussion that as a program, what do we see as the best path forward?

“One of the important areas we’re working on is continuing to develop a feed ingredient import program. What could it look like? What are the pitfalls, issues and challenges that must be overcome, and as an industry do we want to do some form of a standardized approach? It’s the industry’s decision whether to do that, and I’m really excited about SHIP being a model in which industry voices can ultimately make that decision.”