Sunday, May 16

Deadly Pig Disease Could Have Spread Covid To Humans, Analysis Suggests | Environment


An outbreak of a deadly swine disease may have laid the groundwork for Covid-19 to take hold in humans, a new analysis suggests. African swine fever (ASF), which first spread to China in 2018, disrupted the supply of pork and increased the potential for contact with human viruses as people sought alternative meats.

Pork is the main source of meat in the Chinese diet, and the country produces half of the world’s pigs, which generate approximately 55 million tons of pork per year, forming an industry worth more than $ 128 billion (£ 98 billion). The African swine fever outbreak had spread across most of China in the fourth quarter of 2019. The disease is untreatable and incurable. Once it takes hold, the only solution is to kill the infected animals.

The dramatic fall in the supply of pork, after restrictions on the movement of pigs and slaughter led to price increases, increased the demand for alternative sources of meat to transport throughout the country. These sources included wild animals, greatly increasing the opportunities for human contact with the coronavirus, a team of researchers from China and the United Kingdom suggested in a report. still to be a peer-reviewed analysis.

“If more wildlife enters the human food chain, either through [individuals] hunting … or going to the market and obtaining different sources of meat. If that increases, it could increase the opportunity for contact, ”said study author David Robertson, professor of viral genomics and bioinformatics at the University of Glasgow. “It is only increasing the opportunity to [Sars-CoV-2] viruses to enter humans. “

The key to avoiding another future zoonotic pandemic is the Herculean task of figuring out how it happened. Disease detectives, including a team from the World Health Organization, are still on the trail, but many suspect that Sars-CoV-2 likely originated in bats and spread to humans, possibly through an animal. intermediary.

A woman smells the meat before buying it at the Xihua Market in Guangzhou.  The pork shortage following the African swine fever outbreak increased demand for other meats in China.
A woman smells the meat before buying it at the Xihua Market in Guangzhou. The pork shortage following the African swine fever outbreak increased demand for other meats in China. Photograph: Alex Plavevski / EPA

The first cluster of Covid-19 cases was detected in Wuhan, but the disease may have originated elsewhere. In January 2020, Chinese scientists released the genetic sequence of the virus that was renamed Sars-CoV-2. Since then, scientists have shown that the virus likely had at least its distant ancestry in horseshoe bats from China’s Yunnan province.

From a sample of 41 first confirmed cases of Covid-19, 70% of those infected were stall owners, employees or regular customers of the Huanan market, which sold shellfish but also live animals, often illegally caught in the wild and slaughtered. in front of clients. But the first confirmed case had no apparent connection to the market.

The recently published analysis, implicating ASF as a driver of the spread of Sars-CoV-2 to humans, presented a likely explanation for what occurred, Robertson said, noting that ASF could have caused a shortage of about 40-60% from China. total pig population, causing a massive disruption to the country’s meat industry.

“And that potentially explains why there is no direct connection [to the market in previous research]Why is it difficult for us to find the connection, ”he said. “Because with that kind of overflow, you would go to the market and expect to find infected animals still, and that didn’t happen. And then there is a puzzle, there is a kind of missing link. “

At the moment, the idea that the pork shortage caused the Sars-CoV-2 spill in humans was just a hypothesis, he added. “We are showing disruption… imagine a wall, it’s just a brick in that wall of evidence. It is something that we believe should be taken into account in understanding what was developed.

“As is often the case in this type of investigation, it can take many years to unravel the likely routes. [While] it is unlikely that we will ever know exactly what happened; It seems likely that we will find a virus close to Sars-CoV-2 from a bat, [or] maybe another species, “he added.

“And then from that, you can start to say, well, how did that get to humans?”

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