Pangolins, civets and other species are illegally hunted in their natural habitats all the way to Asian markets. Scientists call for the elimination of this trade not only to protect biodiversity, but also to reduce the risk of a new epidemic.
Within weeks of the start of the SARS-CoV-2 epidemic in China, the country in February banned the trade in wild animals for human consumption from its popular markets. The veto prevented the sale of specimens from exotic species farms and illegal trafficking, one of the most lucrative illicit businesses in this region of the world.
The Asian country was joined by Vietnam, after sending an open letter to the prime minister by a dozen environmental associations such as WWF. "It seems clear that transmission has occurred through close contact between humans and wild animals through the ongoing illegal wildlife trade.”, They confirmed.
But, after the end of the two-month quarantine, Chinese markets seem to be operating again despite warnings from the scientific community for years: the illegal trade in wild species has become a massive threat to public health.
“I'm not at all surprised that SARS-CoV-2 has emerged. We know that wild animals carry a wide variety of viruses and that some can be spread in humans. Many of us have been warning about this for years. We can't fail again”Says Edward Holmes, an evolutionary virologist at the University of Sydney, Australia.
From the jungle to the plate
“The outbreak undoubtedly originated in a wet market [with most animals still alive] in Wuhan in China. They are very unsanitary and unsanitary with boxes of different animals stacked on top of each other”Describes Simon Evans, an expert on illegal trade in species at the University of Anglia Ruskin in the UK.
Although it is still difficult to ascertain the origin of SARS-CoV-2, scientists point to the bat as the first transmitter of the virus, which would have reached humans through one or more intermediate species. In this sense, numerous studies point to the pangolin, one of the most trafficked animals in the world.
The meat of this small mammal, whose viruses contain genomic regions related to those of human viruses, is consumed by people and its scales are used in traditional medicine. Almost one million live, frozen, whole or broken specimens have been seized in the last 20 years in ports in Africa, Asia, Europe and the United States.
“The scary thing is that the virus can mutate due to the mixture of viruses of more than one speciesEvans emphasizes. But how could it be transmitted to people?
Transport and consumption: how it is transmitted
According to Jonathan Sleeman, director of the National Center for Wildlife Health of the US agency USGS, wild animals are transported long distances and many of them are illegally trafficked without supervision.
“These animals mix with multiple different species in unsanitary conditions, creating a perfect environment for the pathogens they carry to jump from one species to another.”Describes Sleeman.
Through handling, slaughter and human consumption, these pathogens end up spreading to people. “Inter-species transmission events create opportunities for the virus to mutate and adapt to new hosts, resulting in new pathogens that can be transmitted from person to person.”, He adds.
Added to this is an ingrained Asian popular culture that encourages the use of increasingly sought-after wild animals. "The value of certain animals for their rarity, the financial ability to purchase these products, beliefs in medicinal benefits and hedonic values, result in a high demand”Says Alegría Olmedo, from the department of Zoology at the University of Oxford, in the United Kingdom.
For the experts, it is necessary to establish international norms on the trafficking and trade of wildlife that prevent the transmission of diseases. Governance, supervision, risk assessment and monitoring of wildlife diseases should be improved, as well as disease risk control, sanitation and communication in the markets themselves.
But despite the fact that conservationists have been calling for a ban on these outlets in East Asia for years, making this decision is slow. "Many wildlife products have become symbols, so markets have evolved based on income”Evans laments.
Goodbye to illegal markets to avoid epidemics
To confirm the association of contagion with wet markets, Professor Edward Holmes, along with researcher Yong-Zhen Zhang from the Shanghai Public Health Clinical Center in China, discussed what is known and what is not known about the genomic data of the virus , in a comment published last week in the magazineCell.
Other research groups had already taken environmental samples from the Wuhan wet market where the virus is believed to have originated and obtained genomic sequences from the market surfaces. Phylogenetic analysis revealed that they are closely related to the viruses sampled from the first Wuhan patients.
However, Holmes and Zhang point out that not all the first cases of COVID-19 are associated with the market, so “the story may be more complicated than suspected”.
Given the ability to cross the biological limits of different species and adapt to new hosts, the researchers suggest measures to avoid new dangers.
These include not only monitoring animal coronaviruses in mammals and increasing action against the illegal wildlife trade, but also removing mammals and “maybe” birds from wet markets.
“Wild animal markets must be closed. They are like an accident that can happen at any time. SARS in 2003 was a big warning. Now it has happened againHolmes stresses.
On the other hand, wildlife trafficking is a multi-billion dollar industry, but the cost of inaction and dealing with a pandemic that affects 180 countries runs into billions of dollars. "Even without considering the horrendous human suffering that the pandemic has caused, this is a compelling reason to end this trade in all its forms.Evans emphasizes.
Viruses that circulate among us
“The lessons from SARS and now from COVID-19 are clear: New viruses will continue to pass from wildlife to people as long as the illegal trade and consumption of wildlife continues."Ecologists pointed out to the Vietnamese government in their open letter.
“We discovered that there were a variety of diseases, such as African swine fever, avian influenza and West Nile virus, which are considered to be high to medium risk of introduction and spread in the Republic of Korea.”Explains Jonathan Sleeman in a study published in the magazineTransboundary Emerging Diseases.
According to the survey in the Republic of Korea, the main routes of introduction of pathogens into this country are wildlife migration, international human movement, and illegal importation of wildlife.
In this sense, a work published in the magazinePLoS ONE pointed out that Amsterdam-Shiphol airport in the Netherlands - one of the largest in Europe - is one of the epicenters of the legal and illegal importation of exotic animals on the continent. In assessing the zoonotic risks of imported animals, the scientists compiled a list of 143 "potentially" relevant pathogens.
The researchers suggest learning from experience collectively: “In today's era, diseases in one country may soon spread on a global scale”Says Simon Evans. Monitoring and establishing stricter international regulations could limit our exposure to potential viruses.
“What we need to learn is that once pathogens are passed on to humans, the solution is not quick. If we learn our lesson, we will decrease the chances of new, and possibly more dangerous, outbreaks in the future”, He concludes.