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SINGAPORE – Horseshoe bats carrying coronaviruses very similar to the one that causes Covid-19 have been found outside of China, so the pandemic may not necessarily have originated in the country, scientists say in a new study.
The virus likely reached the Chinese city of Wuhan from elsewhere, said Professor Wang Linfa of the Duke-NUS School of Medicine in Singapore and one of the study’s co-authors.
The study, published on Tuesday (February 9) in the prestigious journal Nature Communications, had found a coronavirus in the horseshoe bat. Rhinolophus acuminatus in Thailand it was 91.5% similar to Sars-CoV-2, the virus that causes Covid-19.
So far, the closest relative to Sars-CoV-2 has been detected in the horseshoe bat. Rhinolophus affinis in the Chinese province of Yunnan, with a genetic similarity of 96.2 percent.
In another study published as a preprint pending peer review in January, the researchers also found: in the horseshoe bat Rhinolophus shameli in Cambodia – coronavirus 92.6 percent similar to Sars-CoV-2.
All three are horseshoe bats of the genus Rhinolophus. There are more than 100 species in this group, which are widespread from Australia to Europe.
Three Rhinolophus Species that have so far been shown to carry coronaviruses linked to Sars-CoV-2 cannot be found in Singapore.
But related species like Blyth’s horseshoe bat (Rhinolophus lepidus) and the horseshoe bat Trefoil (Rhinolophus trifoliatus) can be found here, said National University of Singapore (NUS) mammal researcher Marcus Chua.
The authors of the Nature Communications paper said their findings show that cross-border surveillance is needed to discover the original host of the virus.
Professor Wang, the expert who confirmed that bats were the original carriers of the Sars virus that affected the world in 2003, explained that to determine this, he believes that there must be a genetic similarity of more than 99 percent between Sars genomes. -CoV-2 and the virus in the animal, as was the case during the outbreak of severe acute respiratory syndrome.
The researchers had found that the virus circulating among the civets, the intermediate host, was more than 99 percent similar to that caused by Sars in humans.
Following the Antibody Trail
The authors of the latest study also used serological tests to determine whether bats and pangolins, another animal that has been shown to carry coronaviruses similar to Sars-CoV-2, had neutralizing antibodies against the virus.
Neutralizing antibodies are a special group of antibodies that can help prevent the virus from attaching itself to the host cell and beginning its invasion.
They took blood samples from bats and pangolins in Thailand and analyzed them for the presence of neutralizing antibodies using cPass, a neutralizing antibody kit developed by Professor Wang.
These serological tests are useful for detecting past infections and will not indicate whether the animal is currently infected.
For bats, four of the 98 blood serum samples showed the presence of strong positive neutralizing antibodies. The high level of neutralizing antibodies detected among them suggests that there could be a more related virus in Thai bats, said Professor Wang.
As for the 10 pangolins, whose countries of origin are unclear as they were confiscated by the Thai illegal wildlife trade authorities, molecular tests looking for the presence of viral genetic material came back negative, indicating that none of them was currently infected.
However, one pangolin tested positive for neutralizing antibodies.
Professor Wang said this shows that pangolins are highly susceptible to coronavirus, but it is not yet clear whether they could have acted as an intermediate host or a transmitter.
Wildlife management implications
In November of last year, Denmark decided to euthanize all mink that are raised for their fur in the country, fearing that a mutated form of coronavirus found in mink could hamper the effectiveness of a future vaccine.
But Professor Wang said that slaughter should not be an option for wildlife.
“Active surveillance and monitoring will be the way forward,” he added.
The NUS investigator, Mr. Chua, agreed.
He said that compared to the risk of large-scale animal husbandry, where many animals are in close proximity to humans, the possibility of transmission of zoonoses from wild animals to humans is lower.
“Killing bats is not good because studies have shown that disturbing bats’ habitats and trying to eliminate them could lead to a change in their behavior and can also stress them, which could lead to increased prevalence and spread of the virus,” he said Chua.
Most importantly, humans avoid disturbing wildlife habitats and maintain a respectful distance from wild animals.
He added: “Bats perform important ecosystem services, as they are insect hunters that keep the insect population in balance in the ecosystem, and many are also important seed dispersers.”
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