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Animal sales from Wuhan wet markets immediately prior to the COVID-19 pandemic

Our take —

While bats are the reservoir hosts of SARS-related coronaviruses and the most likely source of the evolutionary ancestor of SARS-CoV-2, the absence of live bats from the market shops implies that other intermediate hosts may have needed to be involved in transmission to humans. The current study provides evidence that wild animal species that are susceptible to SARS-related coronaviruses were sold at markets in Wuhan prior to the emergence of SARS-CoV-2 in November 2019. However, without evidence of viral infection in these animals, their involvement in SARS-CoV-2 emergence remains unknown. Additional studies that investigate viral exposure in potential intermediate host animals being sold or transported to markets or on the farms sourcing markets and the humans in close contact with these animals during transportation and trade are needed to provide additional support for this hypothesis of SARS-CoV-2 emergence.

Study design

Other

Study population and setting

The study reports on observations of live animals sold at markets around Wuhan between May 2017 and November 2019. The surveys were performed as part of a study to identify the animal source of tick borne disease in Hubei Province. A total of 17 shops selling live animals were surveyed within four large markets in Wuhan: Huanan Seafood market, Qiyimen live animal market, Baishazhou market, and Dijiao outdoor pet market. Researchers interviewed vendors to ask about what animal species were sold, in what quantities (either individuals or by weight for some species), the price per unit sold, and the origin of animals (whether wild-caught or captive bred/farmed). The investigators also checked to see if vendors had licenses to sell livestock and wild animal products, which are required by Chinese law, and whether the permits were visible to customers.

Summary of Main Findings

Including animals sold by weight, a total of 47,381 animals were reported from the 17 shops over the time period of the surveys. Most animals were alive when sold and were kept in stacked cages. There were 38 non-domesticated animal species reported from the shops, 31 of which are protected species under Chinese law. No bat species or pangolin species were found for sale in the shops. Of the 38 species, 21 had individuals sourced directly from the wild as inferred from wounds (gunshots or leg-hold traps) or based on interviews with vendors; the remaining 17 species were sourced from farms or captive breeding operations. While 13/17 shops did have the necessary permits for selling wild animal species for food, species names were given in Chinese only and none of the shops posted the origin or quarantine certificates, so were not compliant with legal requirements. Furthermore, vendors displayed 20 species that were caught in the wild that are protected under Chinese law restricting the sale of wild-caught individuals for food, making all sales illegal.

Study Strengths

The primary strength of the study is the uniqueness of the data. The vendors were more transparent with the authors about trading practices than if the investigators had been connected to law enforcement.

Limitations

The authors did not collect samples to test for the presence of viruses in animals being sold at shops. Therefore, we have no information on whether the animals were infected or exposed to SARS-CoV-2 or related viruses. The authors also provided no data on how the numbers of animals sold per species changed over time at each of the markets.

Value added

This study provides unique data on the live animal sales occurring at markets in Wuhan in the time leading up to the first reported cases of COVID-19. Bats (Rhinolophus species) and pangolins are known to carry viruses related to SARS-CoV-2, but none of these were present at the markets. However, four species with known susceptibility to SARS-related coronaviruses were found among the species sold at the markets: raccoon dogs, hog badgers, masked palm civets, and mink. Hog badgers and masked palm civets were important intermediate hosts for SARS-CoV emergence in China in 2001. Experimental infection trials have shown that raccoon dogs are susceptible to SARS-CoV-2. Finally, farmed mink populations experienced massive outbreaks of SARS-CoV-2 in Europe and North America in 2020. While individuals of all four carnivore species sold at markets were sourced from farms, some individual raccoon dogs and hog badgers were wild-caught. The presence of these animals at the markets increases the plausibility of the hypothesis that one or more intermediate hosts may have been the source of SARS-CoV-2 in Wuhan. In such a scenario, animals carrying the virus, having been infected from a reservoir host in the wild or on a farm, were brought to the market and spread the virus to humans involved in the transportation or sale of animals, as occurred for SARS-CoV.

This review was posted on: 19 June 2021