January 25, 2021
New strains of African swine fever in China caused by unlicensed vaccines
China's swine industry insiders said two new strains of African swine fever (ASF) detected in local swine farms are most likely caused by unlicensed, illicit vaccines, the latest setback to the steadily recovering sector, Reuters reported.
Yan Zhichun, New Hope Liuhe's chief science officer, China's fourth-largest swine producer, said the two new ASF strains have infected more than 1,000 sows on several farms owned by the company as well as swine fattened for the company by contract farmers.
Yan said the new strains do not kill swine as it is missing one of two key genes present in the current wild ASF virus, but they cause a chronic condition that reduces the number of healthy piglets born.
Wayne Johnson, a Beijing-based veterinarian, said he had diagnosed a chronic version of ASF among swine last year. This variant did not have certain genetic components known as MGF360 genes. Yan said the new ASF strains discovered by New Hope did not have both MGF360 and CD2v genes.
According to research, deleting the MGF360 genes from ASF creates immunity from the virus. However, the modified ASF virus was not developed into a vaccine because it will mutate to a harmful state.
China's industry insiders and experts said many Chinese farmers have resorted to using unapproved products to protect their swine, creating accidental infections which are now spreading.
The new strains could spread through contaminated meat as the virus can live for months in some pork products. Swine that feed on kitchen waste will be most vulnerable to infection.
China's Ministry of Agriculture and Rural Affairs has issued three warnings against the use of unauthorised African swine fever vaccines, adding that it could have severe side effects and producers and users may be charged with a criminal offence.
The ministry said it will test swine for different ASF strains as part of the country's investigation into the use of illegal vaccines.
- Reuters
