The Department of Homeland Security Science and Technology Directorate (S&T) has been intensifying African swine fever (ASF) vaccine research efforts since November in collaboration with the USDA. The African Swine Fever Task Force was created, based out of S&T’s Plum Island Animal Disease Center (PIADC), to tackle this threat to the swine industry.
“There is no vaccine. In addition to killing most infected pigs, African swine fever also gets into the background in ticks and is very difficult to eradicate,” said Larry Barrett, S&T PIADC director. “The primary focus is to improve diagnostics and vaccines, so pork producers can protect their animals in the future.”
The Department of Homeland Security and USDA work together to intercept pork and other inadmissible agricultural products at all ports of entry. Recently, USDA’s Animal and Plant Health Inspection Service (APHIS) placed stronger import restrictions on pork and instructed the 2,000 DHS Customs and Border Protection (CBP) inspectors to be on high alert for passengers and products arriving from China and other affected countries, according to a news release.
On March 16, CBP seized, with the help of trained USDA beagles, one million pounds of illegal products containing smuggled pork from China at the Port of New York and New Jersey where the government destroyed the entire seizure.
A Look Back at the Fight Against ASF
ASF first emerged in Africa in the 1920s and spread among domestic and wild pigs. In 1957 it appeared in Portugal after pigs near the Lisbon Airport were fed airplane leftovers containing infected pork. Spain was also affected.
As time went on, small outbreaks appeared in other European countries and the Caribbean in the next three decades. In 2007, the viral disease showed up in the Republic of Georgia and spread through the Caucasus region, before it eventually reached China in August 2018, Mongolia in January, and Vietnam in February. Japan detected their first case of infectious African swine fever in late March.
Researchers in the U.S. began studying ASF in the 1970s when the viral disease was spreading through Spain and Portugal. In the 1990s, USDA’s Agricultural Research Service (ARS) started looking for a vaccine. Focusing on the DNA genome of the virus, which contains more than 150 different genes, they began searching for the genes that cause sickness, switching them off and creating a live attenuated vaccine (a weakened virus that induces immune reaction without causing sickness).
“Unfortunately, that research ended in 2004, because we did not have enough funding,” said Luis Rodriguez, the research leader of the ARS Foreign Animal Disease Research Unit, who leads vaccine development in the ASF Task Force.
Research resumed at Plum Island in 2008 under the leadership of Manuel Borca, a world-renowned scientist for his work on ASF, after the disease broke out in the Republic of Georgia.
Scientists are currently testing vaccine candidates and looking for alternative attenuated vaccines at Plum Island.
“The first step toward a vaccine is generating a protective response in pigs,” said John Neilan, S&T PIADC science director.
Researchers are using genetic engineering to create ASF viruses that grow in pig macrophages but are weakened and do not cause disease when inoculated in pigs. Researchers will then test these pigs to determine if the weakened virus induced protection against the wild type virus.
African swine fever virus infects a macrophage, a type of white blood cell.
Several good candidates have been discovered using this method, but a vaccine is far from being ready yet.
“We need a better method,” Rodriguez said. “Part of S&T’s funding is for exploring the existing cell lines to see if we can find any that are promising for vaccine production.”
Improved Diagnostic Testing
The ASF Task Force is working to improve diagnostic testing capabilities for ASF. To support more rapid collection of samples from suspect animals, USDA is evaluating the utility of oral fluid samples for detection of ASF as a population-level test, the release said.
Through an international collaboration with colleagues at the Canadian Food Inspection Agency, APHIS is assessing existing tests for ASF on this novel sample type and expect to have results later this spring.
In another cross-agency effort, USDA and S&T are identifying a quicker way to isolate ASF virus from animal samples.
Why does this matter? Virus isolation is considered a ‘gold-standard’ diagnostic test because it demonstrates that live virus is present in the sample. It also provides an opportunity to amplify the virus for additional future testing, including full-genome sequencing, the release said.
What Does the Future Hold?
Although a vaccine is still years away, once the two current vaccine candidates are transferred to industry partners, Plum Island will help them develop vaccines. Neilan said it will be a success if the Task Force reaches the next step of vaccine development within three years.
“Our vaccine candidates are probably the most advanced in the world,” Rodriguez said. “They are the only vaccine candidates that are based on the Georgia strain. That makes them promising. Our vaccine candidates are definitely in the forefront of science worldwide.”
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