Wildlife trade increases the risk of disease spread… To Us: NPR

In 2003, a shipment of exotic African rodents found in a pet store in Illinois shocked the United States. First outbreak of mpox. Gambian giant rats and other rodents infested prairie dogs, resulting in about 100 people handling the animals becoming infected.

Ebola outbreaks often follow contact with bats, which are sometimes eaten or used for traditional medicine.

More famously, a string of scientific papers There are suggestions that the COVID-19 pandemic originated from the Huanan Seafood Wholesale Market, where hundreds of live wild animals – raccoon dogs, civets, Himalayan marmots – were kept in tight quarters.

Such tales are examples of how the wildlife trade – from buying wild animals for food to trapping them for pets – can open the way for pathogens to jump from animals to humans. A single fatal encounter can lead to the deaths of hundreds, thousands, even millions of people.

says, “There has long been a consensus that the wildlife trade is a threat to human health.” Colin CarlsonA disease ecologist at Yale University. “But most of what we know is from anecdotes.”

Carlson says that strange view makes it difficult to understand how risky wildlife trade is compared to other causes of infectious disease increases, such as climate change or deforestation. Although it makes sense that traded species would infect humans more frequently than non-traded species, scientists cannot answer this question definitively without more data.

Now, Carlson and his colleagues provide answers. are about commercial mammals 1.5 times the chance It is more likely to be a source of human diseases than non-traded animals, researchers report Science. Importantly, the longer humans have been in contact with a species, the more viruses we have in common – especially when dealing with illegal animals and live markets.

“This is a really strong paper that reinforces what we already know,” says Kevin Olivellea disease ecologist at the University of Hawaii who was not involved in the study. “The wildlife trade is indeed a risk for zoonotic diseases. This has been driven by previous outbreaks, including potentially COVID-19, and we need to think about this globally if we want to prevent the next one.

an atlas of pathogens

Five years ago, this kind of study wasn’t really possible, Carlson says.

“The data we have on animals and their viruses (and other pathogens) did not exist,” he says, “at least not in a way that researchers could easily analyze.” Carlson and his colleagues changed that.

They created a database into which they could add every newly discovered virus. By combining this pathogen atlas with data on wildlife trade – including which mammals are traded and how long a species has been involved in – the team can see which mammals share the most pathogens with humans.

The results, although not entirely surprising, were shocking. Of more than 2,000 traded species, 41% shared at least one pathogen with humans, compared to only 6.4% of non-traded species.

Showing that pathogens are shared doesn’t say anything about who did the sharing, but it’s likely that most of these cases arose from pathogens jumping from animals to humans, not the other way around, Carlson says. “Humans are omnipresent. We’re exposed to everything, and we’re picking up more stuff than we’re putting down.”

The researchers found that some parts of the wildlife trade, already considered risky, are particularly conducive to catching the virus.

“Live animal markets are a major risk factor,” says Carlson.

“We’re talking about animals in poor health, crowded conditions, strange combinations of species,” he says. “We know that viruses are evolving in real time in these markets as they move between species.” People working in these markets often do not have the kind of protective gear that can prevent pathogens.

Illegal wildlife trade, involving endangered or protected animals such as pangolins and squirrel monkeys, was also associated with elevated risk of spillover. This may be because such species carry more viruses, Carlson says, or because illegal markets may be more lax in hygiene.

Ultimately, the team found that timing was of the essence. The study found that for every ten years a species spends in the wildlife trade, another new pathogen is entering humans. “That’s significant, and understandable,” says Olivelle, though he wonders whether that trend could be driven by improved pathogen detection.

In total, there are hundreds of species that have been traded for decades or hunted for millennia. “It’s a one-way ticket. In many ways, the toothpaste is out of the tube here,” he says, “and these animal viruses are here to stay with us.”

risk reduction

The results also highlight that taking action now can reduce the risk, says sagan frianta disease ecologist at Penn State who was not involved in the study. “This paper points our attention to how to block the major pathways by which diseases spread from animals to humans. If you can block those pathways, you’ll block a lot of pathogens.”

Globally, this could mean governments cracking down on illegal wildlife trade – for example, increasing surveillance at airports.

But Carlson believes this could ultimately drive more trading underground, making spillovers harder to detect. “We have to choose between criminalizing the trade and pushing it underground, or finding a path to public health in (these) settings.”

Another option is to address the demand for these exotic species, which generates billions of dollars per year.

“Even though it may seem like I’m not involved in the wildlife trade, as an ordinary citizen, you really are,” says Olivelle. The 2003 outbreak of mpox in the Midwest “happened because people were buying animals. So that cute, little furry (exotic) animal in your pet store, maybe think twice about it.”