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Pangolins and the pandemic: a silver lining for the world’s most trafficked mammal?

Pangolins are the world’s most trafficked mammals, but evidence suggesting that they were the source of Covid-19 could put a stop to the trade.

The Coronavirus pandemic has been an anthropogenic disaster – there is no doubt about that.  Life as we know it has changed and the last year has been devastating for countless industries and innumerable individuals.  However, for one animal, the arrival of Covid-19 could carry a faint ray of hope.

Pangolins are one of the world’s most trafficked animals and are thus unsurprisingly endangered.  What is surprising is the proportion of people that are entirely unfamiliar with the species, despite the urgency of their plight.  WWF’s recent campaign to ‘Save the Pangolins’ sports the slogan, ‘The most trafficked mammal you’ve never heard of’.

To look at, they are rather unusual, their features forming a hybrid between those of a reptile, armadillo and anteater.  They are the only mammal with scales and, when threatened, curl up into a ball; the result somewhat resembles an alarmed artichoke.  It is their scales, along with their meat, that they are illegally trafficked for, used for traditional medicine and consumption.

Pangolins curl up in a ball when they feel threatened. © Joel Alves/Shutterstock

However, pangolins have recently been linked to the initial outbreak of Covid-19 in China.  Covid-19’s origin is a central concern; many animals carry coronaviruses and are possible sources of infection and the starting point of any contagion is vital to know, due to the potential to prevent future outbreaks.  The evidence for pangolins being the source of Covid-19 is presently far from conclusive, but it has already prompted action from the Chinese government and, if further measures are taken against the wildlife trade, the incident could be a significant turning point for pangolin conservation.

The world’s most trafficked mammal

Despite their resemblance to anteaters and armadillos, the closest living relations of pangolins are in fact carnivorans, the group that includes wolves and cats. Their diet comprises insects such as ants and termites and they are often nocturnal and elusive.  The protective scales covering their bodies consist of keratin, the same material that makes up our nails.

There are eight species of pangolin, with four living in Africa and the other half residing in Asia.  All eight species are at risk of extinction according to the International Union for Conservation of Nature (IUCN).  Of the African species, two are considered vulnerable and two endangered, while one of the Asian species is endangered and three are critically endangered.  Pangolins are illegally killed and trafficked for two primary reasons: their meat is viewed as a delicacy in several south-east Asian countries, particularly China and Vietnam, and their scales are used in traditional Chinese medicine.

Pangolins are trafficked for their meat and scales, and their skins can also be made into leather products. © Afrianto Silalahi/Shutterstock

The source of Covid-19?

The suggestion that pangolins transferred Covid-19 to humans emerged at a press conference held by the South China Agricultural University in Guangzhou on 7th February, where two scientists, Yongyi Shen and Lihua Xiao, compared coronaviruses from pangolins with those from infected humans.  The genetic sequences were apparently 99% alike.  However, the results had not yet been published, meaning they could not yet be scrutinised by other scientists.

Meanwhile, there were a number of alternative proposals.  The virus could have originated in an animal market in Wuhan, where many species were kept in tightly packed, unsanitary conditions with large numbers of people nearby.  This would be a prime opportunity for a virus to jump from one species to another.  Others placed the blame on bats, since the virus is genetically similar to those occurring in bat species and it would not be the first time that a disease transferred from bats to humans.  There was also a study written that linked the virus to one found in snake species, though this is now believed to be  doubtful.

Over 2.7 million pangolins are poached every year. © Arief Budi Kusuma/Shutterstock

On 20th February, however, the researchers posted a preliminary edition of the study on the pre-print website ‘bioRxiv’.  The conclusions were drastically dissimilar to those portrayed at the conference.  While the pangolin virus was genetically linked to that which was infecting people, it was unlikely to be directly related to the pandemic due to substantial sequence disparities.  The 99% similarity described at the conference only existed in one region of the genome; across the genome as a whole, the similarity was only 90.3%.  The confusion was labelled an ‘embarrassing miscommunication’ between the bioinformatics and laboratory groups within the study and, when the Observer reached out for more information, Xiao refused to comment.

Termination of the trade?

However, despite the mix-up, the Chinese government was already taking action.  On 24th February, China announced an immediate ban on the trading and eating of many wild animals, pangolins included.  Wild animal markets across the country began to be closed down by officials.

This action was the most recent in a sequence of steps designed to reduce the trade.  In 2016, the international pangolin trade was totally banned by the 183 nations that joined the Convention on the International Trade in Endangered Species (CITES).  All eight species were put in Appendix I of the Convention, offering them the firmest protection currently available.

However, this legislation does not seem to have caused a reduction in the number of pangolins traded.  What has changed is the nature of the shipments.  Prior to 2016, frozen pangolin bodies could be found, with the meat smuggled into China from other parts of South-East Asia.  Presently, the majority of shipments solely comprise of scales.  They frequently originate from Africa, having been illegally shipped out via Nigeria.  In 2019, China’s state insurance providers announced that they would cease covering medicines made from pangolin scales, taking effect in January 2020.

Pangolin scales are used in traditional Chinese medicine. ©Asmus Koefoed/Shutterstock

Against this backdrop, it is uncertain what effect China’s new prohibition on eating wild meat will have on pangolins.  Even without the ban, pangolin consumption was forbidden in the country, since pangolins had protected status, reflected in the shift to importing scales rather than meat.  The scales are only legal if they derive from certified sources, but traders often find loopholes.  On a longer term scale, the loss of insurance funding may be more successful at weakening the market.

The real source of Covid-19?

The belief that pangolins played a part in the virus’ emergence among humans has not disappeared.  On 17th March, a team led by Kristian Andersen at Scripps Research in La Jolla, California, published a thorough analysis of Covid-19’s potential origin in Nature Medicine.  The researchers conclude that the ultimate source is likely to be bats, as was the case for the previous two coronavirus outbreaks of recent years: Sars and Mers.  Bats are a recognised reservoir of coronaviruses and, moreover, intermediate horseshoe bats are known to carry a virus called RaTG13, the genome of which is 96% identical to that of Sars-CoV-2.

Horseshoe bats are known to carry a virus that is similar to the coronavirus infecting humans. © Ondrej Prosicky/Shutterstock

The question, then, is how the virus might have travelled from bats to humans and the team are considering two scenarios.  The crucial question is how the virus obtained the certain sequences of its genome that permit it to bind firmly to human cells and infect them, since the bat version of the virus does not possess these sequences.

One possible explanation is that the bat virus jumped to humans several months prior to the detection of the outbreak.  The early viruses would not have been particularly contagious or hazardous, but could have mutated and evolved to attain the crucial genetic sequences that caused them to be so infectious.

The other option is that there was an intermediate host.  This is where pangolins enter the equation.  While the pangolin virus as a whole is less similar to Sars-CoV-2 than the bat version, the pangolin virus genome does possess the necessary binding sequences.  This is what Shen, Xiao and their colleagues discovered and their findings have now been backed up by further studies.  Additionally, a study published on 26 March in Nature discovered viruses closely related to Sars-Cov-2 in pangolins that had been trafficked into China, which had binding sequences comparable to those in the human versions.  While the bat virus is more similar overall, it is different in the significant regions, whereas the pangolin virus is identical where it matters.

Pangolins trafficked into China carried viruses closely related to Sars-Cov-2. © Jiri Prochazka/Shutterstock

This information suggests that the bat and pangolin viruses came into contact, possibly within the same host, and exchanged genes.  Some of the bat viruses ended up with the key binding sequences from the pangolin viruses, allowing them to infect humans.  While the theory is still speculative, researchers believe it to be highly likely.

A similar origin story is associated with the Sars outbreak of 2002-2004.  The source of the virus was wild bats and in 2017 researchers identified a Chinese cave where the bats carry viruses virtually identical to Sars.  However, the virus was most likely passed to humans via civets, cat-like creatures native to tropical Asia and Africa, resulting in the Chinese government enforcing a temporary ban on their sale.  Similarly, the most recent Mers outbreak is thought to have moved from bats to humans via camels.

However, it is not yet certain which scenario is correct.  Even if an intermediate host was involved, it may have been another animal rather than pangolins.

Sars was likely passed to humans via civets – small, mostly nocturnal mammals that live in tropical forests.  © trubavin/Shutterstock

Stopping the demand

The conclusive truth about the potential contribution of pangolins to the Covid-19 outbreak will most likely not be resolved in the near future.  After all, determining the source of Sars took years.  However, it may be crucial to ceasing the pangolin trade, since doing so has two requirements: strict enforcement of the rules and stopping people from buying pangolin products.  China already seems keen to stringently impose regulations and ending the demand means that the illegal trade will become unprofitable and be abandoned by suppliers.

The negative publicity alone may assist in reducing the demand.  Chinese conservation organisations have been circulating a questionnaire on social media to gauge if and how people’s attitudes have altered.  Over 100,000 people have responded and over 90% have said that they would support a total ban on the trade in wild animals, regardless of the intended purpose.  While it is unclear whether people will still adhere to this once the Covid crisis has passed, the understanding that wildlife markets allow the zoonotic spread of diseases may incite action, not only for safeguarding wild animals but also for protecting human health.  In an ideal scenario, not only pangolins but all wildlife will benefit.  Diminishing the demand for illegally traded animals would help numerous species – and shield us from the danger of future pandemics.

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