Coronaviruses extremely widespread in wildlife trade: study
Coronaviruses are extremely widespread in wild animals bred for food in Vietnam, with the wildlife supply chain quickly spreading those viruses to uninfected animals, new preliminary research shows.
The study illustrates how efficiently the $300 billion global wildlife trade amplifies animal viruses and brings them into contact with humans – the exact process most scientists suspect is behind the emergence of COVID-19 at a wet market in Wuhan.
Examples of trafficked wildlife in Vietnam are detailed in the paperCredit:medRxiv
“These results are pretty much what all of us in this business expect,” said Professor Hamish McCallum, a wildlife disease ecologist at Griffith University's Environmental Futures Research Institute.
“If you wanted a way to transfer viruses between species and amplify them, you couldn’t find a better way to do it than wildlife trading.”
Humans are affected by a few hundred viruses; scientists think there may be about 1.67 million viruses circulating in mammals and waterfowl.
Some of those viruses – they don’t entirely know which – can jump from animal to human. Coronaviruses appear particularly capable of making the leap, with strains of the virus responsible for SARS, MERS and COVID-19.
The climate crisis and habitat destruction are pushing animals and humans closer together. When different wild animals are kept in close quarters, viruses can jump between animals, swap genes and then potentially jump into humans.
The new study, done between 2009 and 2014 but only uploaded to medRxiv on June 10, shows exactly how that can happen.
Vietnam has become a major hub of the wildlife trade, much of it bound for China.Credit:medRxiv
The researchers tracked the Vietnamese rat trade – about 3400 tonnes of live rat were processed annually for consumption at the time – at 70 sites, including farms, markets and restaurants.
Vietnam has a significant wildlife farming industry, which rears rodents, boar, snakes, deer, crocodiles for sale to restaurants, much of it destined for China.
They also looked at bats living in 'guano farms', structures often set up near towns so people can harvest the bats' manure as fertiliser.
Among 1506 bats and rats tested, a third of the animals tested positive for bird and bat coronaviruses. Every single rodent market and nearly all bat farms had animals with the viruses.
More troubling, the authors note, was that the percentage of animals with coronaviruses increased as they tracked the supply chain from farm to plate.
That makes sense, said Professor McCallum; cramming the animals together at markets allows the viruses to spread from creature to creature. Stress and lack of food probably increases the animals’ shedding of virus.
The study was co-authored by Australian Wildlife Health Centre senior vet Leanne Wicker.
The sanctuary declined to make Dr Wicker available for interview about the paper, but last week she told The Age and The Sydney Morning Herald : “SARS-CoV-2 virus is not the first significant pathogen to arise from the wildlife trade and it most certainly won't be the last."
A 'guano farm' in VietnamCredit:medRxiv
The study has not yet been through rigorous peer review or published in an academic journal, meaning its findings need to be treated with caution.
The research was funded by PREDICT – a US government-funded program designed to predict the next pandemic.The program was defunded just before COVID-19 emerged.
Australia has been calling for a ban on wildlife markets because they are potential pandemic sources. However, Professor McCallum called this approach potentially counterproductive.
“If you drive wildlife markets underground you’ll lose any ability to regulate them. And there is some neo-colonialism going on here – the Sydney fish market is a wet market. What is necessary is that wildlife markets need to be better managed.”