GOING VIRAL: FROM BATS, TO PANGOLINS TO HUMANS?
Odd animal’s possible link to COVID-19 has reduced the demand for its flesh and scales
In 1820, Lord Francis Rawdon Hastings, the governor-general of Bengal from 1813 to 1823, presented King George III with a most unusual gift. On first glance, it resembled a coat of armour, but it was actually a jacket made from the scales of the pangolin.
What is a pangolin? It’s a curious-looking animal, something of a cross between an anteater and an armadillo that few people in the west had ever heard of before some researchers postulated a connection with the COVID -19 crisis.
There are eight species of this mammal found only in Asia and Africa and all are covered with scales that give the appearance of armour. When attacked by a predator, the pangolin curls up into a ball, protecting its soft underbelly. While a lion, leopard or tiger can do no more than roll the living ball around until it gets frustrated and goes on to look for easier prey, the coiling up does not offer protection from the pangolin’s most dangerous predator, man. The helpless animal is easily picked up and cannot even bite its nemesis since it has no teeth. It does have very long tongue, which is fine for sucking up insects and termites, but is not much of a deterrent for hunters, who club the unfortunate animal unconscious before tossing it into boiling water to loosen its scales.
Pangolin flesh is regarded as a delicacy in Asia and is thought to stimulate the sexual appetite, selling for upward of $600 a kilo. But it is the scales that bring in the big money, fetching around $3,000 a kilo. That’s because roasted and ground up, they are believed to stimulate lactation, improve blood circulation, heal menstrual problems and cure various ailments, even cancer. None of this makes any sense given that the scales are just made of keratin, the same protein that forms the basis of our hair and nails.
Just as nonsensical is the belief that “pangolin wine,” made by boiling baby pangolins in rice wine, heals skin diseases and relieves asthma. Even drinking pangolin blood is said to have medicinal value. Little wonder then that pangolins are poached to such an extent that they have become the most illegally trafficked animal in the world! When COVID -19 first appeared in China, there was a rush for such “traditional medicines,” fuelled by the inability of modern science to offer an effective treatment. However, pangolin products soon lost their appeal after extensive publicity was given to research that seemed to link a virus discovered in these animals to the disease.
Two Chinese scientists found that the genetic sequences of a coronavirus in pangolins matched the sequences in the SARS-COV-2 virus to the extent of 99 per cent. This raised the possibility that the virus had jumped to humans from pangolins, likely through poachers handling live animals. After release of the preliminary results, a more detailed analysis revealed that the 99-per-cent match was only in one region of the virus’s genome and that he overall match was only 90 per cent. This seemed to absolve the pangolin from being the culprit in transmitting the coronavirus to humans and attention focused on various other wild animals that were sold in the so-called “wet markets” in China.
The general scientific consensus is that bats are the original source of the coronavirus since a virus they harbour is a close match for the one that has infected humans. However, there are two issues here. First, humans have limited contact with bats, and second, while the bat virus genome is very similar to the genome of the virus that infects humans, it does not have the genes that code for the proteins that allow the virus to bind to human cells.
This suggests the likelihood of an intermediate host, some animal that happened to harbour a virus that had a sequence coding for the binding protein. If this virus mingled with the bat coronavirus and exchanged some genes, a novel virus capable of infecting humans could have emerged. There is actually a model for this with the original SARS virus that is believed to have been passed to humans from bats through civet cats, likely through the civets being exposed to bat poop. Such a scenario is possible with the current virus as well. And pangolins now re-enter the picture. While the pangolin virus as a whole is less similar to Sars-cov-2 than the bat virus, its genome does have the crucial binding sequences. This raises the possibility that the path may have been from bat poop to pangolin to man. Research may eventually reveal if this is so or not, but the possibility of a link has already deterred people from buying pangolin products, so that for this unusual animal, the cloud of COVID -19 has a silver lining.
By the way, the pangolin coat presented to King George III, replete with its gilded scales is on display in the Royal Armouries Museum in Leeds, England. joe.schwarcz@mcgill.ca