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Saturday, March 6th, 2021

From vaccines to disinfectants, new multi-agency task force tackles emerging threat of African swine fever

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It’s a disease that’s killed millions of pigs globally, crippled farming, and has no cure. African swine fever has devastated the Asian pork industry, as China has culled about half of its total swine population since the disease took hold of that country in August 2018.

Outbreaks of African swine fever — which do not affect human health but cause internal bleeding in pigs — have serious economic consequences. Having the virus can ban an affected nation from the international pork trade, as is the case with China. This is the reason the U.S. government has established a new, multi-agency initiative, an African Swine Fever Task Force based out of the Department of Homeland Security’s Plum Island Animal Disease Center (PIADC), to tackle the threat of the disease before it arrives, if ever, to the United States.

The task force was the vision of officials working with DHS’s Science and Technology Directorate in collaboration with the U.S. Department of Agriculture. The three-year mission of the task force includes everything from creating better diagnostics to identifying vaccine candidates so pork producers can protect their animals in the future.

“The United States is a global leader in pork exports and we’ve never had a case of African swine fever,” said Larry Barrett, PIADC director, adding that the United States exports a third of its pork. “So an African swine fever outbreak would cost billions to control.”

The United States currently produces 115 million market hogs a year with an economic value of more than $20 billion annually, and that doesn’t include the cost of the soybeans and other products needed to feed swine. China’s industry is valued even more as the world’s largest pork producer and consumer.

“I think the spread was rapid in China because they transport pigs large distances there,” said Barrett, who traveled to China just months before the start of the outbreak. “So if you had an infected animal that was transported to market, oftentimes the vehicle hasn’t been cleaned …ultimately the virus spreads everywhere. It spread across China to all their districts.”

Similar to China, the United States transports its pigs thousands of miles each day. And beyond the potential spread of the virus to domesticated pigs is also the threat of the virus infecting the feral pig population, as has happened in China. When the African swine fever virus infects a herd, it kills 95 percent of the animals. So examining the cleanliness of transport vehicles and slaughterhouses becomes crucial in stopping the spread of the virus.

The task force is exploring ways to apply commercially available disinfectants to kill the virus before an outbreak occurs. John Neilan, director of science at PIADC, and his team are organizing scientific trials and assessing the environmental impact of several disinfectants. The research focuses on how these chemicals interact with various surfaces where the virus may reside, such as on concrete, stainless steel, or glass, which may all be used in swine packaging plants, Neilan said.

Farmers have known for more than a century about the dangers of African swine fever but the virus was mainly indigenous to Africa. That changed in the 1970s when the virus spread throughout Spain and Portugal, brought into these countries through cured meats. In the last decade, the disease has moved into pig populations in Europe and in Russia, where it’s suspected the virus then migrated into China.

The rapidly moving nature of the virus is only one of the reasons why African swine fever is so difficult to combat. There’s also the challenge of creating a vaccine. Although Spanish and Vietnamese researchers claim to have developed separate vaccine candidates, the Food and Agriculture Organization and the World Organisation for Animal Health do not yet recognize a vaccine candidate.

It’s complicated to create a vaccine because African swine fever is a large DNA virus containing more than 150 genes. Compare that to foot-and-mouth disease which has only 12 genes, Barrett said. And the number of genes on the surface of the African swine fever virus is not even mapped out.

That has not deterred U.S. scientists from the USDA’s Agricultural Research Service, also part of the task force, from vaccine development based on a live attenuated virus.

The researchers at Plum Island are developing a vaccine that is “scientifically very promising,” Barrett said, however, they are still several years away from a commercially viable option. This is partly due to difficulties developing vaccines in an established cell line, that is, a cell culture that can indefinitely be maintained in vitro, government scientists said in April. That aside, recently published results — though not yet peer-reviewed — demonstrate every pig treated with a prototype vaccine created at PIADC avoided developing significant signs of disease.

Until a finalized form of a vaccine is created, the United States remains vigilant in preventing African swine fever from entering the country, placing stronger import restrictions on pork.

“I’ve seen nothing in my career as serious as this, and I don’t think anything in the last 100 years has killed so many animals as this disease has,” Barrett said. “We’ve got to get this under control.”