By P.J. Griekspoor
The rapid spread of African swine fever in China since it was first discovered there in early August has scientists at the Biosecurity Research Institute on the Kansas State University campus going about research on the deadly virus with a new sense of urgency. They’ve been conducting research on African swine fever for the past three years.
“We have not had cases of this disease in the United States,” says Stephen Higgs, BRI director. “But its introduction would create a disaster. It is nearly 100% fatal, there’s no vaccine and almost no chance of developing a vaccine in the short term. And even one outbreak, quickly contained, could have an enormous market impact.”
While laboratories around the world continue to work toward a clear understanding of the double-stranded DNA virus that causes the hemorrhagic disease and strive to develop a treatment or a vaccine, the people who work to safeguard American livestock from foreign animal diseases have an added level of responsibility.
“Right now, prevention is about all we have,” Higgs says. “Keeping it out of the U.S. is a top priority. But right behind that is making sure that we have a framework in place that would enable quick identification, isolation and eradication.”
African swine fever produces fever in pigs, and in the early stages they will huddle together for warmth and show signs of respiratory distress. It proceeds to a hemorrhagic phase, producing bloody diarrhea, bright red ears and splotches of discoloration on the skin.
The U.S. has about 79 million hogs, mostly in large indoor confined farming operations. Those facilities have high levels of biosecurity, which is a good thing when it comes to exposure to pathogens, but a bad thing for the speed with which any disease that is introduced can spread
U.S. states at greatest risk
Ken Burton, a researcher with BRI, was the project administrator for a research project also involving scientists from K-State’s College of Veterinary Medicine and the Center for Animal Disease Modeling and Surveillance at the University of California, Davis. He has recently published research examining potential pathways for the virus to arrive in the U.S. and the states that are at greatest risk.
Not surprisingly, the states with the highest pig populations — Iowa, Minnesota and Wisconsin — were found to have the highest risk of introduction in live pigs, while California, Florida and Texas are most at risk of introduction through swine products.
The study, which was conducted before the outbreak in China, identified several pathways: legal or illegal imports of live pigs; imports of contaminated pork products; feed, feed additives and pharmaceuticals; and accidental introduction of contaminated food from the feeding of food waste from cargo ships, ocean liners and airlines to swine.
There is also a danger of introduction in feed that is imported from an infected region. That makes the China outbreak of particular concern, since the U.S. does import some soybean meal from China along with a number of vitamin additives, some of which are manufactured only in China.
The National Pork Board has identified 7 basic questions that pork producers should ask their feed suppliers.
Burton says the virus does not affect people, so humans could safely consume contaminated food, but infects pigs by using the food waste from their own table to feed domestic animals. He says a particular danger to the U.S. could be travelers bringing back human food from an infected area, so surveillance has been increased at U.S. Customs stations.
If an outbreak were to occur, quick identification and containment would be essential.
“With a disease that has not been seen before, there is always a danger that the index case will be misidentified,” Burton says. “The natural inclination of producers or veterinarians is to first think of a disease more familiar to them. With a disease as virulent as this one, a delay of days in identification can lead to astonishing spread.”
Higgs says researchers at BRI have been familiar with the characteristics of the virus and its extraordinary ability to survive and replicate.
“We have seen how fast it can spread, how lethal it is and how extraordinarily complex it is. It has a long lifespan and can withstand heat, cold and even some cooking processes,” Higgs says. “It lives in live pigs; survives in the carcass; survives even in some cured meats, such as ham; is present in some areas in the feral pig herd; and can be spread by ticks,” he says. “It is a formidable pathogen.”
There is no effective vaccine for ASF, Higgs says, and there is little hope that one will be ready in the near future.
The outbreak in China, which is home to half of the world’s swine population — some 700 million pigs — is particularly alarming, as is the rapid increase in outbreaks reports since Aug. 1, when it was first detected. It has now been confirmed in 14 separate outbreaks in six provinces. The infected sites are hundreds of miles apart, leaving researchers baffled about what is causing the spread.
Romania’s Veterinary Health & Food Safety Authority said Sept 13 that 230,000 pigs had been slaughtered and that 900 outbreaks have been reported around the country, with the southeast the worst affected.
The Food and Agriculture Organization of the United Nations convened an emergency session on Sept. 7 in response to the rapidly increasing outbreaks and concluded that there is a “high probability” that the outbreak in China will spread to Asian neighbors, notably the Korean peninsula.
Virus has been around since 1921, has not hit U.S.
African swine fever is not a new virus.
It was first seen in Africa in 1921 and is considered endemic across much of sub-Saharan Africa. It remained confined to the African continent until 1957, when an outbreak was reported in Portugal. It was believed to be eradicated, but a second recurrence happened in 1960 that resulted in it being endemic across the Iberian Peninsula (Portugal and Spain) until 1995.
In the 1970s and ‘80s, outbreaks occurred in the Netherlands, Italy, France and Belgium; and in the Western Hemisphere in Cuba, the Dominican Republic, Haiti and Brazil. Feeding of contaminated pork products is believed to have fueled that spread.
The disease can also affect wild pig populations, a major factor in areas where it is endemic. It is the only DNA virus known to have an arthropod vector — soft ticks.
“There is a real danger that any significant outbreak can make it extremely hard to eradicate because it can get into the feral pig herd, and the ticks that carry it have a long lifespan,” Higgs says. “That’s one reason it can appear to be eradicated in an area, then pop back up.”
In some wild pigs and in older hogs, the disease has been known to take a less-lethal, chronic form that kills fewer pigs but increases the potential host reservoir.