Outdoor Pigs

Outdoor pig farms and feral hogs is one way ASF can spread, but humans moving pigs and contaminated pork move the disease much faster. Photo by the Pork Checkoff.

Unauthorized experimental vaccines against African swine fever are being used on pig farms in China, creating “chaos” because of their varying levels of efficacy, Caixin reported.

No vaccine has been proven safe and effective against the deadly hog virus, yet at least three illegally procured products have been used to immunize millions of hogs, the magazine said Nov. 12, citing a veterinary expert and other unidentified people involved in the pork industry in Jiangsu province.

The vaccines were deployed after farmers signed confidentiality agreements with suppliers, leading to large losses in some cases and creating “chaos,” Caixin cited another veterinary expert in the southern province of Guangdong as saying.

The effects of the vaccines were highly variable. Some immunized pigs later developed a condition causing their skin tissue to die; some pregnant females aborted; others suffered no side effects, but died en masse from the disease, according to the report.

The use of illegal vaccines by some farms has amplified the challenge of eradicating African swine fever in China, Zhang Guihong, a professor of veterinary medicine from South China Agricultural University, told a swine conference last month.

Different types of vaccines have been simultaneously used in some areas, making it difficult to discern their safety and efficacy, and distinguish between vaccinated and unvaccinated pigs, she said.

China’s agriculture ministry said in September that experimental, homemade or even smuggled vaccines could bring unpredictable biological safety risks to the country. It also warned farms not to use overseas vaccines as China’s epidemic strain belongs to so-called genotype 2, and vaccines based on other virus strains could worsen the situation.