A new strain of African swine fever recently identified on Chinese pig farms was likely caused by “illicit vaccines,” industry experts said this week.
In the absence of an approved vaccine for African swine fever, “many Chinese farmers struggling to protect their pigs have resorted to unapproved products,” Reuters revealed on Tuesday, citing industry insiders and experts who “fear illicit vaccines have created accidental infections, which are now spreading.”
Two new strains of African swine fever have infected over 1,000 sows across several farms owned by China’s fourth-largest pork producer, New Hope Liuhe, in recent weeks. Pigs being fattened for New Hope by contract farmers have also been infected by the new virus strains, New Hope chief science officer Yan Zhichun told Reuters on Tuesday.
“I don’t know where they come from, but we find some mild field infections caused by some sort of gene-deleted viruses,” Yan said.
A Beijing-based veterinarian named Wayne Johnson said he diagnosed a chronic, and less lethal, form of African swine fever in pigs at Chinese farms in 2020. The virus strain diagnosed by Johnson “lacked certain genetic components, known as the MGF360 genes,” according to Reuters. The two new African swine fever variants recently detected at New Hope are “missing both the MGF360 genes and the CD2v genes,” according to Yan.
“Research has shown that deleting some MGF360 genes from African swine fever creates immunity, but the modified virus was not developed into a vaccine because it tended to later mutate back to a harmful state,” Reuters noted.
“You can sequence these things, these double deletions, and if it’s exactly the same as described in the lab, it’s too much of a coincidence, because you would never get that exact deletion,” Lucilla Steinaa, principal scientist at the International Livestock Research Institute in Nairobi, told the news agency.
While no cure or approved vaccine for African swine fever exists, China said in August that it was close to approving the first vaccine candidate for the virus.
China is the world’s largest producer of pork. The country’s pork industry was devastated by previous strains of African swine fever that swept Chinese pig farms in 2018 and 2019. China is still recovering from the deficit caused by the outbreaks, which wiped out 40 percent of the country’s pig population. The Chinese government is currently working to both rebuild China’s pork supply and protect it from future outbreaks.
The Chinese Ministry of Agriculture and Rural Affairs launched a crackdown on the production and use of illegal or fake African swine fever vaccines in late August, advising the public that provincial authorities would soon carry out “inspections at veterinary laboratories, drug producers and pig farmers for any evidence they could have developed or used an illegal vaccine.”
Authorities will “investigate veterinary laboratories used for research or commercial purposes and check any unlabelled vaccines and disease materials or reagents along with the records of experiments,” the agriculture ministry said at the time.
The Chinese state-backed newspaper Legal Daily reported last May that police in China’s southwestern city of Chongqing had “arrested seven people found to be producing a fake African swine fever vaccine.”