Progress reported in race to find vaccine for deadly hog disease spreading across China

Key Points
  • The race is underway to find a vaccine that can control African swine fever, a highly contagious and deadly viral infection ravaging China's hog population.
  • No treatment or effective vaccine is available for the swine fever, but some encouraging news is reported this week.
  • The Chinese plan to start clinical trials on a vaccine, Reuters reported Friday, citing state media.
  • U.S. scientists also have several gene-edited vaccine candidates against African swine fever, and researchers in Spain recently report progress on an oral vaccine for wild hogs.
Pigs are seen in a hog pen in a village in Linquan county in central China's Anhui province Friday, Aug. 31, 2018.
Barcroft Media | Barcroft Media | Getty Images

The race is underway to find a vaccine that can control African swine fever, a highly contagious and deadly viral infection ravaging China's hog population. No treatment or effective vaccine is available for the swine fever, but some encouraging news was reported this week.

A government-run research facility in China developed two vaccine candidates that were proven in laboratory tests to provide immunity to the deadly pig disease, Reuters said Friday, citing a report originally from Beijing state media. The report also offered promise given clinical trials are planned.

"In the next step, the Chinese Academy of Agricultural Sciences will accelerate the progress of pilot and clinical trials, as well as vaccine production," said the report, based on an online posting by China National Radio.

Beijing hasn't divulged the exact number of hogs lost to swine fever, but Rabobank last month estimated up to 200 million animals could be affected and production could decline by 30%. That compares with about 75 million hogs and pigs in the total U.S. inventory.

Outbreaks of African swine fever also have been reported in other Asian countries, including Vietnam, Cambodia and Mongolia, as well as in Europe and Africa, where it was first identified more than a century ago. It comes amid worries the swine disease could reach the U.S. and cause significant economic impacts and the loss of exports.

African swine fever is expected to be a topic of discussion at the World Organisation for Animal Health's five-day annual meeting in Paris starting Sunday. The UN-affiliated agency tracks the spread of swine fever and sets standards for international trade in animals.

In this May 8, 2019, photo, a pig walks through a nearly-empty barn at a pig farm in China's Hebei province.
AP Photo | Mark Schiefelbein

Last week, the U.S. Department of Agriculture announced a new "surveillance plan" for African swine fever. The plan includes the testing of "high-risk animals," such as sick or dead pigs as well as herds exposed to feral swine or garbage eating. Experts say the swine fever doesn't pose a risk to humans.

USDA scientists also are intensifying research on a vaccine for African swine fever. Three gene-edited vaccine candidates have been developed so far with the help of the agency's veterinary microbiologists.

Manuel Borca, the lead scientist in the USDA's Foreign Animal Disease unit at Plum Island Animal Disease Center in New York, said all three of the vaccine candidates are based on the most prevalent African swine fever strain currently circulating in Europe and Asia. Two candidates, though, are being modified further so that researchers will be able to distinguish between infected pigs and vaccinated animals.

Even as vaccine candidates continue to be evaluated, the federal government is beginning collaborations with vaccine manufacturers, according to USDA scientist Luis Rodriguez, the research leader at the Foreign Animal Disease unit. He said the goal is "to fully develop a vaccine that is safe, efficacious and allows differentiating vaccinated from infected animals (a key feature during disease eradication programs)."

Rodriguez estimates the timeline for the full development of vaccine candidates will take years and hinge on many factors, including the availability of a large-scale manufacturing process as well as confirmation of efficacy in field vaccine trials.

In Spain, meantime, scientists have reported progress toward an oral vaccine for wild boars, according to a study published last month in Frontiers in Veterinary Science. They found that a strain of the African swine fever virus protected 92% of orally vaccinated animals.

"Our observation that three wild boar were immunized through contact indicates that orally vaccinated animals can shed [the] vaccine virus," according to the study, done under the direction of Jose Manuel Sanchez-Vizcaino, a professor in animal science at the University of Madrid. He wasn't available for an interview for this story.

The testing on wild boars is seen as significant because movements of disease-carrying wild hogs have contributed to the spread of African swine fever in the Baltic and Eastern Europe region. Also, there's a risk of virus transmission to domestic pig herds.

European wild boar suckles young.
AP Photo | Heribert Proepper

According to the study, "this protection translated not only to animal survival but also to the absence of ASF-compatible clinical signs, pathological findings, and virus detection in target tissues."

But some scientists caution against too much optimism.

"Theoretically, the vaccine could work as well for commercial pigs," said Paul Sundberg, a veterinarian and executive vice president of the Iowa-based Swine Health Information Center. "There are issues with that vaccine, however, that I don't think you'll see it being used either in wild boar or certainly not in commercial pigs in the near future."

Sundberg said there are more than 20 different strains of African swine fever and added what works in wild boars may neither be effective nor safe in domestic pigs. Moreover, there's a risk the virus used in the vaccine could mutate, become virulent and cause a more severe strain.

As for China, Sundberg raised concerns that Beijing's desperate effort to halt the spread of African swine fever in its pig population could involve risky or dangerous research in the laboratory.

"It's an attempt to find something to stop this virus," he said. "That attempt in itself can be very dangerous, because it might propagate the virus, that might perpetuate the virus, and that might ensure that it becomes endemic."