As COVID-19 spreads around the world, a common question is: Can infectious diseases be linked to environmental changes? Yes, according to a study published today by the University of California, Davis’ One Health Institute.
Exploitation of wildlife by humans through hunting, trade, habitat degradation and urbanization facilitates close contact between wildlife and humans, increasing the risk of spreading viruses, a study published April 8 in the magazine was published. Proceedings of the Royal Society B† Many of these same activities are also reducing wildlife populations and risking extinction.
The study provides new evidence for assessing spillover risk in animal species and highlights how the processes that lead to population decline in the wild also enable the transmission of animal viruses to humans.
“Virus overflow from animals is a direct result of our actions involving wildlife and their habitat,” said lead author Christine Kreuder Johnsonproject director of USAID FORECAST and director of the EpiCenter for Disease Dynamics at the One Health Institute, a program of the UC Davis School of Veterinary Medicine. “As a result, they share their viruses with us. These actions simultaneously threaten the survival of species and increase the risk of overflow. In an unfortunate confluence of many factors, this is causing the kind of mess we are in now.”
The Ordinary and the Rare
For the study, the scientists collected a large dataset of the 142 known viruses that pass from animals to humans and the species that have been implicated as potential hosts. The habits IUCN Red List of Threatened Species, they examined patterns in those species abundance, extinction risks, and underlying causes of species decline.
The data shows clear trends in spillover risk that show how humans have interacted with animals throughout history. Among the findings:
- Domestic animals, including livestock, have shared the highest number of viruses with humans, with eight times more zoonotic viruses compared to wild mammal species. This is probably a result of our frequent close interactions with these species over centuries.
- Wild animals that have increased in abundance and have adapted well to human-dominated environments also share more viruses with humans. These include some species of rodents, bats and primates that live among humans, near our homes, and around our farms and crops, putting them at high risk of continued virus transmission to humans.
- At the other end of the spectrum are endangered and threatened species. This includes animals whose population decline has been linked to hunting, wildlife trade, and the decline in habitat quality. These species were predicted to contain twice as many zoonotic viruses compared to endangered species whose populations were declining for other reasons. Endangered and endangered species are also often well managed and directly controlled by humans trying to bring about their population recovery, which also leads to more contact with humans. Bats have been repeatedly implicated as a source of “high impact” pathogens, including SARS, Nipah virus, Marburg virus and Ebola viruses, the study said.
“We have to be very attentive to how we interact with wildlife and the activities that bring people and wildlife together,” Johnson said. “Obviously we don’t want pandemics of this magnitude. We need to find ways to coexist safely with wildlife, because they have no shortage of viruses to give us.”
The study’s co-authors are Peta Hitchens of the University of Melbourne’s Veterinary Clinic and Hospital, and Pranav Pandit, Julie Rushmore, Tierra Smiley Evans, Cristin Weekley Young and Megan Doyle of the EpiCenter for Disease Dynamics at UC Davis One. Health Institute.
The study was supported by funding through the USAID Emerging Pandemic Threat PREDICT program and the National Institutes of Health.