BEIJING (Reuters) – A new form of African swine fever identified in Chinese pig farms is likely to be caused by illicit vaccines, industry insiders say, a new blow to the world’s largest pork producer, which is still recovering from a devastating epidemic of the virus.
Two new species of African swine fever have infected more than 1,000 sows on several farms owned by New Hope Liuhe, China’s fourth largest producer, and pigs fattened by the firm’s contract farmers, said Yan Zhichun, chief scientific officer, said. .
Although the strains, which contain one or two important genes missing from the wild African swine virus, do not kill pigs like the disease that plagued China’s farms in 2018 and 2019, they cause a chronic condition that reduces the number of healthy piglets . born, Yan told Reuters. At New Hope and many large producers, infected pigs are eliminated to prevent the spread, which effectively kills the disease.
Although the known infections are now limited, it can reduce the production of pork in the world’s best consumer and producer if the strains spread widely. two years ago, swine fever wiped out half of the 400 million pig herds in China. Pork prices are still at record levels and China is under pressure to strengthen food security amid the COVID-19 pandemic.
“I do not know where they come from, but we do find some mild field infections caused by some gene-removed viruses,” Yan said.
Wayne Johnson, a veterinarian in Beijing, said he diagnosed a chronic or less deadly form of the disease in pigs last year. The virus does not have certain genetic components, known as the MGF360 genes. New Hope found strains of the virus lacking both the MGF360 genes and the CD2v genes, Yan said.
Research has shown that the removal of some MGF360 genes from African swine fever creates immunity. But the modified virus did not develop into a vaccine, as it tends to mutate back to a harmful state later.
“You can follow these things, these double deletions, and if they are exactly the same as what is described in the laboratory, it’s too much of a coincidence, because you will never get the exact deletion,” said Lucilla Steinaa, chief scientist at the International Livestock, said. Research Institute (ILRI) in Nairobi.
There is no approved vaccine for African swine fever, which is not harmful to humans. But many Chinese farmers struggling to protect their pigs have resorted to unapproved products, industry experts said. They fear that illegal vaccines have accidentally caused infections, which are now spreading.
The new strains can spread worldwide through contaminated meat, infecting pigs fed with kitchen waste. The virus is known to survive for months in some pork products.
The Chinese Ministry of Agriculture and Rural Affairs did not respond to two requests for comment.
But it has issued at least three warnings against the use of unauthorized vaccines against pigs in Africa and warned that it could have serious side effects and that producers and users could be charged with a criminal offense.
In August, the ministry said it would test pigs on various strains of the virus as part of a nationwide investigation into the illegal use of vaccines.
Any strains with no-removal may indicate that a vaccine has been used. No findings have been published so far on the issue, which is very sensitive to Beijing. The coverage of the recent outbreaks of swine fever in Africa has been extensively covered up. Click here for a link to the report
MAN-MADE TEAMS
After decades of research into the manufacture of a vaccine against the enormous, complex swine fever virus, researchers around the world are focusing on live virus vaccines – the only species that have shown any promise.
However, such vaccines carry higher risks, because even after the virus has been weakened so that it does not cause serious diseases, it can sometimes be virulent again.
One such vaccine used in Spain in the 1960s caused a chronic disease with swollen joints, skin lesions and respiratory problems in pigs, which hampered efforts to eradicate African swine fever in the next three decades. Since then, no country has approved a vaccine for the disease.
A vaccine with both MGF360 and CD2v genes removed is being tested by the Chinese Harbin Veterinary Research Institute after it showed promise.
Yan said he believes humans have replicated the series of virus strains studied, which have been published in scientific literature, and that pigs injected with illegal vaccines based on them could infect others.
‘It was certainly made by man; it is not a natural tension, ”he said.
Neither Johnson nor Yan fully succeeded the new swine fever strains. Beijing strictly controls who may work with the virus, which can only be handled in laboratories with a high biosecurity rating.
But several private companies have developed test kits that can examine specific genes.
GM Biotech, based in central Hunan province in China, said in an online report last week that it had developed a test to identify whether the pathogen is a virulent strain, an attenuated strain with a single gene, or ‘ a weakened stem with a double gene.
The test helps pig producers because the new strains “are very difficult to detect in the initial stage of infection and have a longer incubation period after infection,” the company said.
The government did not say how many legal vaccines were used or who manufactured them. But a “large number” of pigs in China have nevertheless been vaccinated, Johnson said, a sentiment expressed by many other experts.
In 2004-5, when the H5 bird flu strains spread across Asia, Chinese laboratories produced several unauthorized live bird flu vaccines, said Mo Salman, a professor of veterinary science at Colorado State University who worked on animal health in Asia, said. fear that they may yield dangerous new varieties.
“The current ASF illegal vaccine (s) in China are repeating history,” Salman said.
Reporting by Dominique Patton. Edited by Gerry Doyle