Project to identify infectious diseases among mammals sold at wildlife markets reveals the perfect conditions to spark a new pandemic
ByNicola Smith, ASIA CORRESPONDENT11 April 2022 • 12:00pm
When a team of international scientists embarked on a project to identify infectious diseases among animals sold at wildlife markets across Laos, they were alarmed at the “ubiquity” of bacterial pathogens they found.
Wet markets, ranging from small roadside stalls to sprawling warehouses full of live produce, are infamous for keeping stressed wild animals in crammed conditions, ready to be butchered and sold for human consumption.
But while they have long been considered “disease incubators”, the coronavirus pandemic has thrown a fresh spotlight on their prevalence in much of the developing world and the threat they still pose.
In nine wildlife trading hotspots and two roadside stalls in Laos, researchers collected more than 700 samples from wild animals, predominantly squirrels.
Among the pathogens lurking in the specimens was Leptospira, which causes flu-like chills and muscle pains and is one of the main causes of fever in rural Laos. More than one fifth of the tested animals were infected.
“These findings suggest a substantial risk for exposure through handling and consumption of wild animal meat,” concluded the research team, co-led by Dr Pruksa Nawtaisong and Dr Matthew Robinson – both specialists in molecular microbiology of zoonotic pathogens that can infect humans.
But they stressed that their study was “only a small snapshot in time and locality,” and cautioned that “for a significant impact, surveillance should be done over a longer period of time over a wide geographical area.”
Even as the world struggles to move beyond the devastation of Covid-19, scientists are warning that without tighter regulation of the global live wildlife trade, the next pandemic is around the corner, and it could be deadlier.
Covid-19 is largely believed to have emerged naturally from a zoonotic spillover – jumping from bats, possibly via an “intermediary host species” to humans. Prevailing theories suggest that the Huanan seafood market in Wuhan, China, which was known to sell wildlife, could be the pandemic’s ground zero.
If so, Sars-CoV-2 would join the long historical list of pathogens – from the Black Death and Spanish flu to HIV and Ebola – that have been passed from animals to humans.
Yet across the world the trade in birds and mammals, which creates the conditions for future disaster, continues unabated.
The risk of zoonotic spillover rises among those living or working in close quarters with high-risk species, which have been identified in scientific studies as nonhuman primates, bats, small rodents, pangolins, civets, mongooses and badgers.
Horseshoe bats, which are considered the reservoir of many zoonotic diseases, inhabit much of China and Southeast Asia. A recent study by the Chinese Academy of Sciences and University of Hong Kong revealed that nearly 40 per cent in the region are unknown species.
Yet few lessons have been learned from the current pandemic, say experts like Prof. Vincent Nijman, an anthropologist and wildlife trade expert at Oxford Brookes University.
“I think the best we can hope for is luck. And then you also know that at some point you will run out of luck, it will happen again. It is not a matter of if, it is a matter of when,” he said.
Between May 2017 and November 2019, when Sars-CoV-2 is presumed to have first infected humans via an unknown animal host, more than 47,000 animals from 38 species, including racoon dogs, amur hedgehogs and marmots were sold in Wuhan’s wet markets, according to an analysis by Nature.
China issued a ban on such markets and wildlife consumption in February 2020, but the rife wildlife trade, both legal and illegal, across Asia, Africa and Latin America continues on such a vast scale that the risk to humans is evident.
“The real wildlife trade is measured in millions if not billions of individuals, and kilograms and containers, so the scale of it is humungous,” said Prof Nijman. “You start understanding that perhaps checking everything is not an option and that the checks we are doing right now may not be sufficient.”https://cf-particle-html.eip.telegraph.co.uk/20a29606-6af9-40e3-8204-b0639b51c37a.html?i=0&ref=https%3A%2F%2Fwww.telegraph.co.uk%2Fglobal-health%2Fscience-and-disease%2Fnot-matter-scientists-alarm-ubiquitous-pathogens-wildlife-trade%2F&channel=globalhealth&id=20a29606-6af9-40e3-8204-b0639b51c37a&isapp=false&isregistered=false&issubscribed=false&truncated=false<=false
In the Laos study, published in April in the journal Emerging Infectious Disease, researchers focused between 2014 and 2017 on testing animals – mainly squirrels – at nine wildlife trading hotspots and two roadside stalls, working with the Wildlife Conservation Society which has carried out previous similar studies.
“I do think this gives us a good idea of the situation in Southeast Asia as well as valuable insights that could be translated to other geographic localities,” said Dr Robinson, who leads the Molecular Bacteriology Team at the Lao-Oxford-Mahosot Hospital-Wellcome Research Unit in Vientiane.
The study was part of a growing body of work by the scientific and conservation community on bushmeat and zoonotic diseases with the aim to try to “switch to longer-term surveillance type projects” and provide “an early-warning system for potential outbreaks,” he said.
“In terms of actual research, the missing part of the puzzle at the moment is directly linking these pathogens in wildlife to disease in humans,” he added.
“It is very difficult to show that jump taking place without being there at the right place, and at the right time, and certainly more work is needed in this area, to give us a better understanding of how and why.”
The ideal solution – stopping the wildlife trade altogether – was not feasible, but the limiting of the sale of wildlife at markets and improving conditions to reduce transmission risks a “must.”
Legislation and checks could help ensure only uninfected wildlife enters the food chain, and increasing consumer awareness would have a major impact, he added.
But efforts to create an early warning system were being hampered by a lack of funding for the intense surveillance, skills and screening that would be needed. “Long-term investments in government-led wildlife disease surveillance systems is a key part of the solution,” said Dr Robinson.
Last week the World Wildlife Fund sounded another alarm bell after its own investigation found that during the pandemic lockdowns of 2020 and 2021, the online illegal wildlife trade in Myanmar increased by 74 per cent.
The sales of mammals included not only critically endangered species like the Sunda pangolin, but also commercially bred civets – the animal identified as the intermediate host of the virus that caused the Sars outbreak in Asia in 2002.
However, scientists like Prof Nijman, who has worked extensively in Indonesia, caution that the legal wildlife trade poses a far greater risk because its sheer volume vastly overshadows criminal trading.
“There is this very strong emphasis on the illegal wildlife trade, assuming that it is the illegal wildlife trade that we have to worry about when it comes to zoonotic disease. There’s absolutely no reason to assume that the illegal trade is more dangerous than the legal one,” he said.
“So, if you want to make it safer you really have to start thinking about the whole trade chain,” he said. “Levels of traceability, hygiene, and checking needs to improve and that requires investments.”
Dr Sue Lieberman, vice president of the international policy for the Wildlife Conservation Society, and formerly head of the US government’s CITES Scientific Authority, said more needed to be done to change public behaviour and the desirability of eating wildlife.
Wildlife for consumption was often seen as a “luxury item” and not as a food security issue, she said.
“We’ve been talking to a number of countries about when they do their overseas aid – like the UK and the US – that they need to connect it to preventing pandemics in closing these markets,” she said.
“That’s not punitive. It’s – ‘we’ll help you with building your healthcare systems, we’ll help you with reducing poverty, but we need to work together to close these markets’,” she explained.
“We have nearly eight billion people on the planet. We can’t keep rolling the dice and hoping it doesn’t happen.”
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