Dustin Oedekoven, DVM and chief veterinarian with the National Pork Board, spoke to The Pig Site's Sarah Mikesell about the risk that African swine fever poses to the US.

Preventing the entry of African swine fever (ASF) into the US has been a concern for the US swine industry for several years. Since ASF was recently identified in the Dominican Republic and Haiti, that concern has been greatly elevated. Oedekoven said biosecurity is key to ASF control because it is a unique and complicated virus, and vaccine development has been slow, even though important progress has been made on that front.

Oedekoven explained that the virus was historically found only on the African continent and was maintained in the wild pig population due to a soft tick. Between the tick and the pig there is a constant cycle of virus transmission, he said.

The ASF virus also spreads through direct contact between pigs, and it can spread through fomites or other things that carry the virus residually, he added.

One of the ways ASF is transmitted is in pork meat that is not completely cooked or cured, where the virus can survive for an extended time, Oedekoven noted. People transport undercooked pork products and then the meat is discarded or fed to pigs through garbage feeding, thus transmitting the virus across country boundaries, he added.

Once a pig has been exposed to the virus there’s a variety of symptoms that can result. Some strains spread rapidly, others not so rapidly. Ultimately, exposure results in a hemorrhagic disease which causes bleeding in the pig’s organs and ultimately death. When a farm is infected with ASF, typically those animals are depopulated, he explained.

No treatment for ASF

Unfortunately, there’s no treatment for ASF yet as the virus is in a category all by itself, Oedekoven said. That's important because there isn't another similar virus in either animals or humans that can be studied to develop a body of knowledge from which to build on and develop a vaccine, he added. Also, it’s a large virus and coding for several proteins makes it very difficult to create a vaccine, he added.

“And while there's been some really good progress in that area of vaccine development, we currently don't have a vaccine available that would prevent or help us respond to this virus,” he explained.

However, scientists at the Plum Island Animal Disease Center have made positive progress towards a vaccine candidate, Oedekoven said. A vaccine candidate has passed a key milestone in the ‘reversion of virulence test’ which shows that this modified live virus does not cause disease in the pigs. “That will allow that vaccine candidate to go on to further development, most likely first in Vietnam, where African swine fever virus has been identified,” he noted.

Importance for trade

ASF is a notifiable disease to the World Organization for Animal Health (WOAH). The US, as a member country of the WOAH, is obligated to report any identification of that virus, he said.

ASF is a trade limiting disease, which makes it an economically significant disease, Oedekoven noted. There’s global interest in preventing its spread across nations and keeping it out of the global pig herd. Having ASF limits the movement of live pigs and pig products and the ability to trade internationally, which is a good reason, in and of itself, for keeping ASF out of the US, he concluded.