African Swine Fever Vaccine Progress in China Raises Questions

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An African swine fever (ASF) vaccine is proving to be safe and effective in laboratory tests at China’s Harbin Veterinary Research Institute. 

The institute, which is overseen by the Chinese Academy of Agricultural Sciences, said the live vaccine with reduced virulence was created from a series of gene-deleted viruses using the country’s first ASF strain as a backbone, Bloomberg reports.

But U.S. experts caution that this study has been done on a different strain of ASF than the Georgia 2007 strain circulating in China and parts of Europe.

According to the article published in the journal, Science China Life Sciences, the virulence, immunogenicity, safety and protective efficacy evaluation in specific-pathogen-free pigs, commercial pigs and pregnant sows indicated that one virus, namely HLJ/18-7GD (which has seven genes deleted), is fully attenuated in pigs, cannot convert to the virulent strain and provides complete protection of pigs against lethal ASFV challenge. 

“Our study shows that HLJ/-18-7GD is a safe and effective vaccine against ASFV, and as such is expected to play an important role in controlling the spread of ASFV,” the journal article said.

However, Dave Pyburn, DVM, chief veterinarian for the National Pork Board, doesn't believe this vaccine is the answer for the United States post outbreak here.

"In China there is a lot of pressure to find a vaccine, especially one that will allow pigs to survive when infected with ASF. Many in China are pushing hard for good news in the form of pigs living to market and to get this good news out into the field. I don’t think this is the vaccine answer for us especially since Chinese researchers are seeing pigs spiking fevers when vaccinated, the fact that it’s a different strain, infected vaccinated pigs may be shedding virus, etc.," Pyburn says. 

Perhaps the best thing that came out of this study was that scientists were able to culture this virus in porcine bone marrow. The U.S. has been looking for alternative culture media that could be used in vaccine manufacture so this finding is welcomed, Pyburn says.

Vaccine progress underway

The American Society for Microbiology reported earlier this year that U.S. government and academic experts have developed a vaccine against ASF that proved 100% effective. In a recent study published in the Journal of Virology, both low and high doses of this ASF vaccine were 100% effective against the virus when the pigs were challenged 28 days post-inoculation, according to the Jan. 23 release from the American Society for Microbiology.

However, it’s still years away from being commercially available.

In China, the development of official vaccines has been prioritized after unauthorized experimental vaccines against the disease were used to immunize millions of hogs in the country last year. China’s ministry of agriculture said experimental, homemade or even smuggled vaccines could present biological safety risks to the country.

The agency also strongly discouraged farms from using overseas vaccines as vaccines based on other virus strains could worsen the situation.

ASF is deadly for pigs but is not harmful to humans. Since it first broke out in China in 2018, the country’s hog herd has fallen by nearly half as global researchers work furiously to develop the world’s first ASF vaccine.

More from Farm Journal's PORK:

Results Show Promise for Experimental African Swine Fever Vaccine

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