The wet market sources of Covid-19: bats and pangolins have an alibi

From Professor David Macdonald

To date, over 3.5 million people have died from Covid-19. It is therefore of global importance to understand their origins in order to prevent future such pandemics. Covid-19, officially known as SARS-CoV-2, is a coronavirus, and in the past, these coronaviruses have come to affect humans through spill-over from wildlife sources. Such was the case with the 2002 Middle East Respiratory Syndrome (MERS) outbreak in Jeddah, Saudi Arabia, which spilled over with dromedaries and killed 858 people; likewise the SARS-CoV epidemic (for which there is still no cure), which began in Guangdong in 2002 and killed 744 people transmitted by civet cats as a mediator and which transmitted the infection from cave-dwelling horseshoe bats.

We had collected data gathered from all of Wuhan’s wet markets … which our team was in the right place at the right time to document the wildlife sold in those markets in the lead-up to the pandemic

Unsurprisingly, the finger of blame has been placed on the wildlife trade in the humid markets of Wuhan, Hubei, China, where this Covid-19 outbreak appears to originate. Candidate species include bats, which are final hosts that brew coronavirus, and both pangolins and palm civets as potential mediators; although the latest genetic data suggests that the variant found in these latter species is not quite similar enough to the human variant to be a completely compelling source. Nonetheless, the World Health Organization (WHO) dispatched an investigation team to Wuhan from January 14th to February 10th this year, where part of their job was to determine post hoc which animals were being sold in the markets before the closure. Your report was inconclusive but drew attention to the particular need to monitor the bats and pangolin trafficking.

Our investigation revealed that both bats and pangolins had an alibi – none was there!

Working with our colleagues from China West Normal University, Nanchong, and the Hubei University of Traditional Chinese Medicine, Wuhan, Xiao Xiao and Zhao-Min Zhou on site in China, the WildCRU team collected data from all of Wuhan’s wet markets was collected in May 2017 and November 2019. This research, which began before Covid-19 moved these markets into the spotlight, was actually backed up by a study on tick-borne (no person-to-person transmission) severe fever with thrombocytopenia syndrome motivated, our team in the right place at the right time to document the wild animals sold in these markets in the run-up to the pandemic. Our research, published today in Nature-Scientific Reports, found that both bats and pangolins had an alibi – there wasn’t one!

Caged marmots over a cage with hedgehogs, Huanan seafood market before closing

Bats are actually rarely consumed in central China, where market photos generally depict Indonesia. The pangolin trade is still a major issue in other Chinese cities and trading hubs, but not in Wuhan. What was there, however, was 47,381 individuals of 38 species, including 31 protected species, all kept in dire conditions and teeming with all sorts of other infectious diseases, ready to be slaughtered or not sold as pets if necessary. While pork for the equivalent of c. At $ 5.75 / kg in Wuhan, a groundhog would cost $ 25. Badgers and raccoon dogs were a bit cheaper for $ 15-20 or a hedgehog snack for $ 2-3. Among the birds, peacocks were popular for $ 56, or when reptiles were the order of the day, sharp-nosed vipers were available for $ 70 / kg. Pets included everything from squirrels ($ 25) to myna birds ($ 300). Then of course it is not about bushmeat for a living, but an expensive delicacy.

Given these tremendous concentrations of different species under one roof, while we haven’t found any evidence of an original spread of bat or pangolin candidates in Wuhan, it seems only a matter of time before another undesirable disease skips the human population. In fact, it is estimated that around 70% of all diseases that affect humans come from animals, think bird flu, HIV, Ebola, etc.

Faced with this risk, on January 26, 2020, China’s ministries commendably temporarily banned all wildlife trade as a precautionary measure until the end of the COVID-19 pandemic. Subsequently, on February 24, 2020, the eating and trading of terrestrial wild animals (non-livestock) was permanently banned. These interventions, designed to protect human health, resolve past trade and enforcement disputes, will have side effects on global biodiversity conservation and animal welfare, and will hopefully prevent some future tragedies.

Professor David Macdonald is Director of WildCRU, part of the Department of Zoology, University of Oxford

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