Coronavirus: Wet markets a matter of wildlife and death for humans

COVID-19 is just the latest deadly disease to emerge from animals and be spread to humans.

The Tomahon exotic wildlife market in Sulawesi, Indonesia. Picture: Agung Maupa

On a busy Saturday at Indonesia’s Tomohon “extreme market”, Mawar made a beeline past the freshly butchered carcasses of pigs, dogs and rats for the table of half-cooked bats where the rows of spread wings and bared fangs told a uniform tale of difficult death.

The North Sulawesi housewife’s family enjoys a meal of bat meat, known locally as paniki, after church most Sundays, she tells Inquirer, as do many of their neighbours who consider it a delicacy

“I don’t see why we should be afraid of it. If we cook it properly, there won’t be any virus on it,” she says.

Well-cooked bat meat does eliminate a lot of the viruses carried by a species responsible for at least five deadly new diseases seen in recent years — lyssavirus, Ebola, Nipah, severe acute respiratory syndrome and COVID-19.

But as more than three million people infected with the coronavirus will attest, that does not protect humans from infection in the processes leading up to Mawar’s Sunday lunch. All who hunt, trade and slaughter wildlife are vulnerable to the transmission of unknown viruses that have adapted for centuries within these species. Perhaps no one is more exposed than those who work in the wildlife wet markets of Asia and Africa, such as Tomohon, which trade in live and fresh-killed wildlife and domestic animals.

Scientists have been warning for years of the potential catastrophic consequences of bringing exotic wildlife species and domestically reared animals into close contact with each other, and humans.

“These markets are the ideal Petri dish for viruses to jump into domestic-reared animals that are close to us, or directly into humans,” says Ramanan Laxminarayan, director of the Washington and Delhi-based Centre for Disease Dynamics, Economics and Policy. “Wildlife wet markets are a total recipe for disaster and always have been.”

A wildlife wet market in southern China — as distinct from regular wet markets selling fresh vegetables, seafood and poultry — was the origin of the 2002 coronavirus SARS outbreak. Another in Wuhan is the suspected origin of the COVID-19 pandemic that has killed more than 233,000 people.

As Chinese health officials first struggled to understand the pneumonia-like disease gripping Wuhan in late December last year, one of the first things they did was close down the Huanan seafood market that sold, along with live seafood and poultry, exotic animals such as civets, rats, snakes and wolf pups.

Chinese disease control officials quickly notified the World Health Organisation and World Organisation for Animal Health that the market was the likely source of the virus, given many of the first patients had some contact with it. That theory has since disappeared from Beijing’s official narrative as it seeks to shift blame for the outbreak, though China has notably announced a ban on the trade and consumption of wild animals.

Whether or not it was in Huanan market that COVID-19 first jumped from a horseshoe bat perhaps to an intermediate animal and then into human cells is “almost immaterial”, says Australia’s Chief Veterinary Officer, Mark Schipp. “We know the previous SARS outbreak arose out of a wet market and there is circumstantial evidence that was the case here.

“We know a number of pandemic diseases have arisen out of wildlife, including AIDS, MERS, Nipah, so it seems a basic first principle to try not to create a scenario where this would emerge again,” he tells Inquirer.

As OIE president, Schipp is pushing for a global study into whether the zoonotic risks inherent in wildlife wet markets can be mitigated, or if the markets should be phased out, and he has written to all OIE member nations urging support for the move.

“The last two pandemics passed through intermediate mammal species — civet for SARS and probably pangolin for COVID-19 — but a number of diseases pass directly from bats to people such as Nipah virus, rabies and lyssavirus.

“There is a reason why we have domesticated species and that is because they are well-adapted to our environment and usually don’t transmit disease to us.”

The virus we now know as COVID-19 is one lucky pathogen. Every living species on the planet — plants, animals, even other viruses — contains its own set of viruses but it takes a confluence of events to allow that virus to jump from one species to another and survive the migration. Most of the time it hits an evolutionary dead end in the human immune system.

But live wildlife markets and wildlife wet markets, where captured and stressed wild animals are caged and slaughtered alongside species they would seldom otherwise have contact with, provide a near perfect environment for transmission.

Stressed wildlife shed large amounts of virus in bodily fluids — blood, faeces, urine, saliva — that are easily transmitted to animals and humans in proximity.

“In a wet market typically they wash down at least once a day, which aerosolises the virus and creates (further) opportunity to spread between species,” adds Schipp.

Even outside those markets, the harvesting and transport of wildlife — often alongside other species — creates a similarly receptive environment for infection.

Last week Australian Agriculture Minister David Littleproud urged his G20 counterparts to back the OIE study into whether markets could be safely regulated or if they should be phased out with the support of wealthier nations. The government also has written to the WHO suggesting it pass a resolution at its world congress this month recognising the risk of viral spillover from animals and the need for a multidisciplinary approach to address those risks.

The US has gone further, calling for a global ban on wildlife wet markets to prevent future pandemics.

The WHO also supports a ban on the sale and trade of wildlife for food but stresses ordinary wet markets that conform to stringent food and hygiene standards should be allowed to operate.

Littleproud acknowledges the distinction.

“Wet markets are very important for food security in many parts of the world and in no way do we want them shut down. We want the wildlife part of these markets phased out but we need to do that using good science,” he tells Inquirer.

“This is not just about China, which has already shut down wildlife wet markets.

“We are not making this a point of conflict, but we have an opportunity to collaborate with other nations to better understand the risks of these wildlife wet markets and find better outcomes for human health and agricultural systems.”