UNLICENSED VACCINES PRODUCED CHINA’S NEW SWINE FEVER STRAINS

A new form of African swine fever identified in Chinese pig farms is most likely caused by illicit vaccines, industry insiders say, a fresh blow to the world’s largest pork producer, still recovering from a devastating epidemic of the virus, Dominique Patton reported for Reuters.

Two new strains of African swine fever have infected more than 1,000 sows on several farms owned by New Hope Liuhe, China’s fourth-largest producer, as well as pigs being fattened for the firm by contract farmers, said Yan Zhichun, the company’s chief science officer.

Though the strains, which are missing one or two key genes present in the wild African swine fever virus, don’t kill pigs like the disease that ravaged 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 culled to prevent the spread, making the disease effectively fatal.

Although the known infections are limited now, if the strains spread widely, they could slash pork output in the world’s top consumer and producer. Two years ago, swine fever wiped out half of China’s 400 million-head pig herd.

Pork prices are still at record levels and China is under pressure to strengthen food security amid the COVID-19 pandemic. “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.

Wayne Johnson, a Beijing-based veterinarian, said he diagnosed a chronic, or less-lethal, form of the disease in pigs last year. The virus lacked certain genetic components, known as the MGF360 genes. New Hope has found strains of the virus missing both the MGF360 genes and the CD2v genes, Yan said.

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.

“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,” said Lucilla Steinaa, principal scientist at the International Livestock Research Institute (ILRI) in Nairobi.

In 2004-5, when the H5 bird flu strains were spreading across Asia, Chinese laboratories produced several unauthorised live bird flu vaccines, said Mo Salman, a professor of veterinary medicine at Colorado State University, who has worked on animal health in Asia, raising fears that they could produce dangerous new variants. “The current ASF unlawful vaccine(s) in China is repeating history,” Salman said.

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