Trafficked pangolins can carry coronaviruses closely related to pandemic strain

New research finds evidence that a small proportion of pangolins carry coronaviruses related to the strain responsible for the COVID-19 pandemic, according to a paper published March 26 in the journal Nature.

This makes pangolins the only mammals other than bats known to be infected by the closest relatives of the novel coronavirus. While the work neither proves nor disproves that pangolins are linked to the current pandemic, it does indicate that they could play a role in the emergence of new coronaviruses.

“If there is one clear message from this global crisis, it's that the sale and consumption of pangolins in [live animal] markets should be strictly prohibited to avoid future pandemics,” says Paul Thomson, a conservation biologist who co-founded the nonprofit Save Pangolins.

Bats are the most likely reservoir of the novel coronavirus, SARS-CoV-2, according to the World Health Organization, but it likely jumped to another species before spilling over into humans.

Pangolins—endangered, scaly, ant-eating mammals found in Asia and Africa about the size of domestic cats—are known to carry coronaviruses, Dan Challender wrote in an email. Challender heads the pangolin specialist group of the International Union for the Conservation of Nature, which sets the conservation status of species. It’s not surprising, therefore, that they’ve become a focus in the search to understand where the novel coronavirus came from, he says.

Although international commercial trade of all eight species is strictly forbidden, pangolins are believed to be the most trafficked mammal in the world. The scales of thousands of pangolins are smuggled every year for use in traditional Chinese medicine, and their meat is considered a delicacy by some people in China, Vietnam, and elsewhere in Asia. Because coronaviruses can be transmitted by certain bodily fluids, feces, and meat, the trade in live pangolins for food is a greater concern for disease spread than contact with scales.

In China, it’s illegal to eat pangolin, but it can still be found on restaurant menus there. Pangolins were also regularly available for sale at live animal markets until January 26, when fear of the novel coronavirus spurred the government to order them all closed.

Genetic similarities

The new paper finds that the genetic sequences of several strains of coronavirus found in pangolins were between 88.5 percent and 92.4 percent similar to those of the novel coronavirus.

Starting with tissue samples from 18 Sunda pangolins seized in anti-smuggling operations in 2017 and 2018, researchers tested for the presence of coronaviruses. They found it in samples from five of the 18 pangolins. They repeated the process later with samples from other seized pangolins, finding coronaviruses in a portion of those individuals as well. They then sequenced the genomes of those viruses and compared them to SARS-CoV-2.

Cautious in their wording, the researchers note that the genomic similarities “are not sufficient to suggest” that pangolins are the intermediate host that passed SARS-CoV-2 from bats to humans. But they don’t rule it out, either. The paper concludes, however, that pangolins should be considered as possible hosts for future new coronaviruses.

“I welcome the study,” Challender wrote. “Further research is needed on these viruses in pangolins, but importantly on other species too, which may have played a critical role in the transmission of SARS-CoV-2 to humans.”