Study Finds Traded Mammals 1.5 Times More Likely to Carry Human Pathogens

A new study examines the risks of zoonotic diseases from the wildlife trade, which involves the sale of wild animals for food, traditional medicine, pets, and other purposes, both legally and illegally. The research, led by Colin Carlson, a disease ecologist at Yale University, was published in the journal Science.

It quantifies the association between traded mammals and pathogens that can infect humans.

Historical outbreaks illustrate these risks. In 2003, a shipment of exotic African rodents to a pet store in Illinois led to the first mpox outbreak in the United States, where Gambian giant rats infected prairie dogs, which then infected nearly 100 people who handled the animals. Ebola outbreaks have been triggered by contact with bats, sometimes consumed or used in traditional medicine.

Scientific papers suggest the COVID-19 pandemic originated at the Huanan Seafood Wholesale Market in Wuhan, China, where live wild animals including raccoon dogs, civets, and Himalayan marmots were kept in cramped conditions.

The study compiled databases of pathogens from mammals and aligned them with data on wildlife trade, including which species are traded and the duration of human interaction with them.

Researchers analyzed over 2,000 traded mammal species and compared them to non-traded species. 5 times as likely to be sources of human diseases than non-traded mammals. 4% of non-traded species. The longer humans have interacted with a species, the more viruses they share, particularly with illegal trade and live markets.

The study notes that while shared pathogens do not specify transmission direction, most cases likely involve jumps from animals to humans due to widespread human contact.

animal markets were identified as a major risk factor, involving animals in poor health, crowded conditions, and unusual species combinations where viruses can evolve and spread between species.

Workers in these markets often lack protective gear. The illegal wildlife trade, which includes protected species such as pangolins and squirrel monkeys, also contributes to these risks. Colin Carlson stated that prior knowledge relied on anecdotes, making it difficult to compare wildlife trade risks to other factors like climate change or deforestation.

Kevin Olival, a disease ecologist at the University of Hawai'i not involved in the study, described the paper as reinforcing known risks from zoonotic diseases in wildlife trade, including past outbreaks like COVID-19. The databases created for this study, which include newly discovered viruses, were not available five years ago in an analyzable form.

This pathogen atlas enables future research on wildlife trade and disease emergence.

The findings underscore the need for global measures to mitigate these risks and prevent future outbreaks.