New man-made strains of African swine fever are spreading in Chinese pig farms due to the use of illegal vaccines. The disease caused by the strains is not deadly but is expected to hurt pork output in the world's top producing country.
Yan Zhichun, chief science officer of New Hope Liuhe, China's fourth-largest pork producer, said that two new strains of African swine fever have infected more than 1,000 adult female pigs on several farms owned by the firm, as well as pigs being fattened for the company by contract farmers.
The strains are missing one or two genes and do not kill the pigs like the strain that blighted Chinese farms in recent years. Because infections are mild, officials believe that the use of unauthorized vaccines might have caused the outbreak.
But the strains still cause a chronic condition that has decreased the number of newborn piglets and has forced New Hope to cull infected sows. If the outbreak is not contained, the disease is expected to slash China's pork output.
New swine flu strains likely emerged from vaccines
Experts suspect that the new strains may have originated from illicit, faulty vaccines. Beijing-based veterinarian Wayne Johnson said that he detected a less lethal form of African swine fever last year. The virus lacked genetic components known as the MGF360 genes. The strains at New Hope, according to Yan, are missing these genes as well as another set called the CD2v gene.
"I don’t know where [the strains] come from, but we find some mild field infections caused by some sort of gene-deleted viruses," Yan said.
Last year, China's Harbin Veterinary Research Institute (HVRI) developed a live vaccine for African swine fever with missing MGF360 and CD2v genes. The vaccine, which uses a weakened form of the virus, is the first of its type to show promise. But it carries high risks because it can revert to its wild-type form or mutate to become infectious again.
A similar type of jab was used in Spain in the 1960s. It caused a chronic disease in pigs that worsened the outbreak over the next three decades. Since then, no nation has approved a vaccine for African swine fever.
Yan suspects that some people replicated the DNA sequences of the virus and that pigs injected with illicit vaccines based on these sequences may be infecting others.
"It’s definitely man-made. This is not a natural strain," Yan said.
Though African swine fever does not affect humans, it is wildly contagious and deadly in pigs. Industry insiders said, many Chinese farmers are turning to unapproved products to protect their hogs.
Mo Salman, a professor of veterinary medicine at Colorado State University with experience working on animal health in Asia, said that Chinese laboratories produced several unauthorized vaccines for Asian bird flu strains from 2004 to 2005. He raised concerns back then that these jabs could produce dangerous new variants. Now, he's sounding the alarm once again.
"The current [African swine fever] unlawful vaccines in China is repeating history," Salman said.
Beijing withholding outbreak data
Beijing is withholding information about the new strains, replicating its handling of the outbreak that led to the COVID-19 pandemic.
Last August, China’s Ministry of Agriculture and Rural Affairs had tested pigs for different strains of the virus as part of a nationwide investigation into illegal vaccine use. But no findings about it have been released so far. Beijing also refused to disclose who produced the illegal vaccines and how widely they had been used.
China's secrecy brings back the early days of the pandemic. Leaked recordings of a meeting with the World Health Organization confirmed that the Communist government withheld or delayed information about the Wuhan coronavirus, the pathogen that causes COVID-19. Before this, China also under-reported outbreaks that led to the African swine flu epidemic in 2019, according to Reuters. (Related: Chinese authorities hid the fact that medical staff in coronavirus-hit city were infected.)
This epidemic decimated half of China's 400 million pig herd. Global pork prices hit record levels and remain high to this day. If the current outbreak is not contained, China's pork output is expected to suffer another blow, with effects that can ripple through the global supply chain.
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