Underground ASF Vaccines in China: What’s the Risk?

Unauthorized experimental vaccines against African swine fever (ASF) are being used on some pig farms in China, creating concern because of their varying levels of efficacy, reports Bloomberg.

Although no vaccine has been proven effective and safe against this deadly virus that affects both domestic and wild pigs, at least three illegally procured products have been used to immunize millions of hogs, the article said. 

The vaccines were administered after pig farmers signed confidentiality agreements with suppliers, leading to major losses in some situations, a veterinary expert in the southern province of Guangdong was quoted as saying.

The vaccine effects vary – some immunized pigs later developed a condition that caused their skin tissue to die, some females aborted, some had no side effects but died from the ASF virus, the report says.

Using illegal vaccines could magnify the challenge of eradicating ASF, experts say.

“Veterinarians and producers are desperate for a solution. But if the safety of these vaccines is not proven, this could backfire and complicate the situation in Asia further,” says Gustavo Lopez, DVM, now a Ph.D. student studying influenza at the University of Minnesota College of Veterinary Medicine. Lopez battled ASF in Russia for seven years while he managed animal health for a large swine company. 

Different types of vaccines have been used simultaneously in some areas of China, making it difficult to discern individual vaccine safety and efficacy, yet alone distinguish between vaccinated and unvaccinated pigs, Zhang Guihong, a professor of veterinary medicine from South China Agricultural University, said at a swine conference.

The lack of protocols leaves many questions unanswered.

“Even if the vaccine is effective, the vaccine needs to be safe,” Lopez says. “This means that it won’t kill the vaccinated pigs or transmit disease to other pigs and start another epidemic.”

In September, 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, Bloomberg reports.

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