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PCR is the definitive test for African swine fever in China

13 September 2019, at 3:06am

China continues to confirm new cases of African swine fever (ASF) using PCR diagnostics as they work to contain the virus by limiting pig movement and increasing biosecurity on farms.

Dave Pyburn, VP of Science and Technology with the National Pork Board, speaks to The Pig Site's Sarah Mikesell in Des Moines, Iowa.

Dave Pyburn, Vice President of Science and Technology with the National Pork Board, said he receives updates through a number of sources of information - officially through the Chinese government and the OIE (World Organisation for Animal Health) and also from veterinarians and others who travel to China.

“When I talk to folks they get hung up on the number of provinces and the number of outbreaks, but it’s probably not important. I think we need to consider that for the most part, the virus has now become endemic in China,” Pyburn said.

He said the Chinese response – the shutting down of [pig] movements, attempts to control of movement of the virus and fomites, and enhanced biosecurity precautions – all point toward treating ASF an endemic situation.

“The very unfortunate thing about ASF is that it is a high mortality disease when it breaks in pigs, and again pigs are the only species that become affected or infected with ASF. It's not a disease of cattle, it's not a disease of poultry, and it's certainly not a disease of humans,” he explained.

Pyburn said he’s seeing reports of high levels of mortality in the breaking herds in China, but there are still some pigs that survive, who are potential carriers either in the wild or on-farm.

“What they're doing right now is what any of us would have to do in the face of an outbreak with ASF,” he noted. “They're working to eradicate it on those farms that break, which means they come in and it's 100 per cent depopulation of the farm, 100 per cent disposal of those pigs, then biosecurity on that farm to clean up and make sure they get any virus that might be left behind.”

ASF Diagnostics

When ASF breaks in a new province or area in the world, an official report is sent to the OIE.

“You report to the OIE that you have the virus, and that's all done with PCR testing,” he said. “When they get PCR positives on animals, confirmed PCR positives in new farms or in new provinces, that's what spurs them to go ahead and report to the OIE that they've got a new outbreak in a new province that's broke so PCR is the definitive test in this case.”

“As we look to prepare for maybe having to deal with this [in the US], I hope we don't, but if we have to deal with it, we want to be prepared,” Pyburn said. “I've talked with officials at the USDA, and I've asked, “What is our testing regime that we're going to put into place to have proof that we have the virus if we do? What kind of testing do we have to do?" And what I was told is it would be two PCR tests positive, and then we'll declare an official positive.”

PCR testing is important because it identifies finds the DNA from the virus.

“We're not looking for antibody that could potentially be antibody from something else,” he said. “What the PCR test is doing is it's looking for viral DNA and when it finds it, it spurs a positive on that test and so it's actually looking for the virus. If you see it you know you have either live or dead virus, but you know you have African swine fever virus in that pig.”

To read more about China’s use of PCR, click here.

For more information about swine diagnostics, click here or connect to the Thermo Fisher Scientific Swine Resource Center.