The wildlife trade encompasses a lot, from pet sales to food and furs. However, a study from Science estimates that nearly half of traded wildlife carry at least one pathogen that can cause diseases among humans, making this the first to quantify the role of traded wildlife in pathogen transmission.
Several disease outbreaks in humans have been linked to traded wildlife, such as the Ebola epidemic and the COVID-19 pandemic. However, complete data on pathogens in the wildlife trade have only recently emerged in response to the COVID-19 pandemic. The study is the “first global quantitative evidence of that link”, says Jérôme Gippet, an ecologist at the University of Fribourg in Switzerland.
To understand the role that wildlife trade has had on pathogen transmission, Gippet and his colleagues combined over 40 years of records from three wildlife-trade data sets with CLOVER, a dataset that lists various pathogens found in different species. The team focused on mammalian species because of their key role in the wildlife trade and their history of transmitting pathogens to people. The team then created models to predict the risk of pathogen spread through trade interactions, accounting for various circumstances that can influence transmission, such as the proximity of the animals to human communities and how the species are used.
The team discovered that of 2,079 traded mammal species, around 41% shared at least one transmissible pathogen with humans, compared to 6.4% of nontraded animals. The trade of live animals increases the likelihood of pathogens being spread from animals to humans as well. On average, a species shares an extra pathogen with humans every decade that it is present in the wildlife trade.
Not all pathogens humans encounter lead to COVID-scale pandemics or outbreaks. Some do not harm humans or are not capable of human-to-human transmission. However, any increase in exposure to pathogens increases the risk of a virus or bacterium developing into something more concerning.
Regulating this trade is difficult since different countries and cultures have distinct definitions of “wild” animals. However, Arinjay Banerjee, a virologist at the University of Saskatchewan, suggests asking communities to improve hygiene and safety at wildlife markets to decrease the risk of pathogen transmission.
Increasing global disease surveillance and using predictive models to determine which pathogens should be a research priority is a way to prepare for potential disease outbreaks. The authors of the study hope their research inspires more preparation.
“It’s easy to kind of fall into the trap that if you were to magically stop the wildlife trade tomorrow, then there wouldn’t be more pandemics,” says Jonathan Kolby, an applied research ecologist at the Smithsonian’s National Zoo & Conservation Biology Institute. “But even if you erased all of that, we’re still left with this massive, massive domestic and international trade in domesticated animals, which is often also a source of zoonotic pathogens.”
