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A new study has suggested that Sars-CoV-2, the virus that causes Covid-19, may have originated from a recombination of the coronavirus in a bat and pangolin. The findings strengthen the theory that pangolins could be the intermediate host for Sars-CoV-2 transmission to humans.
The document, published in the journal Nature by researchers at the Faculty of Veterinary Medicine at the Agricultural University of South China, also points out that pangolins, which are the most trafficked mammal in the world, could be a future threat to public health. if the wildlife trade is not controlled because they harbor Sars-CoV-2-like viruses.
A coronavirus isolated from Malaysian pangolins by a team of Chinese scientists showed an amino acid identity of 100%, 98.6%, 97.8%, and 90.7% with Sars-CoV-2 in 4 genes.
The Malay pangolin coronavirus was found to be particularly identical to Sars-CoV-2 in its spike protein receptor binding domain (which SARS-CoV-2 uses to bind to the cells of its host).
Genome sequencing found that pangolin-CoV was very similar to SARS-CoV-2 and Bat Sars-CoV RaTG13 (from which SARS-CoV-2 is suspected to have originated), but the only difference was the spike or the S. gene
Further analysis of the S gene sequences has suggested recombination events on May 8.
For this study, the team used lung tissues from four Chinese pangolins and 25 Malaysian pangolins at a wildlife rescue center during March-August 2019. The RNA of 17 of the 25 Malaysian pangolins was found to be virus-positive similar to Sars-CoV-2 and gradually showed signs of respiratory illness, such as shortness of breath, emaciation, inactivity, and crying.
Of 17, 14 pangolins died later.
In general, a natural reservoir host does not show severe disease, while an intermediate host may have clinical signs of infection, the authors said.
Pangolins and bats are nocturnal animals, eating insects and sharing overlapping ecological niches that make pangolins the ideal intermediate host for some Sars-related coronaviruses.
The document recommended more systematic and long-term monitoring of coronaviruses in pangolins and a complete ban on illegal trade in pangolins, international cooperation and strict regulation against the consumption of bushmeat and wildlife trade.
“Of particular interest here is that the entire genome of the pangolin coronavirus is not similar to Sars-CoV-2, but they are almost identical in the receptor binding area (which the virus uses to bind to the cells of its host). Interestingly , the Sars-CoV-2 genome is 96% similar to the bat coronavirus RaTG13 (found in the intermediate horseshoe bat) but differs at the receptor binding site (meaning that RaTG13 cannot directly infect human lungs because their receptor cannot bind to human lung cells. Gather these two pieces of information together and you will come to the hypothesis that has the most support so far, “said Rohit Chakravarty, a wildlife biologist and student at PhD at the Leibniz Institute for Zoos and Wildlife Research in Berlin, Germany, who read the newspaper.
That is, a bat coronavirus jumped from a bat to a Malay pangolin (in the wild or in captivity), the virus recombined in the pangolin and incorporated the pangolin coronavirus receptor binding region, and then evolved into Sars -CoV- 2 that causes Covid-19 in humans, “he added.
Pangolins are trafficked because their scales and blood are believed to have medicinal properties, and their meat is considered a delicacy in parts of Southeast Asia.
“As many reports have shown, pangolins are now the most trafficked wild animal species in the world. As with all wildlife trade, the answer to how it can be controlled is quite complicated, because the flow chain runs through various layers of society. Ultimately, we are all guilty because the scale of operations is directly related to wealth in consuming countries. It is very easy to say that the Chinese eating habits are responsible for all the current problems we face. However, it is much more difficult for us to recognize that, in reality, the consumer lifestyle of all developed and developing economies is the engine that drives this thriving trade, “said Abi Tamim Vanak, member of the Wellcome Trust / DBT Program India Alliance and senior member at Ashoka Trust for Research in Ecology and the Environment.
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