Domestic animals a major link in spread of viruses among humans and wildlife – study

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New research by Swansea University discovered that livestock are of central importance for the spread of both RNA and DNA viruses. Photo: Swansea University

Domesticated animals, both pets and livestock, hold the key to the spread of viruses among humans and wildlife, according to fresh research.

For the study, researchers assessed patterns of virus-sharing among a large range of mammals, including humans and domestic species.

Dr Konstans Wells and his colleagues analysed a global database that compiled the associations between 1785 virus species and 725 mammalian host species.

“We show that based on current evidence, domesticated mammals hold the most central positions in networks of known mammal–virus associations,” they wrote in the journal Global Ecology and Biogeography.

The study also revealed that patterns of how viruses are shared between humans and wildlife species differ between the two major groups of RNA and DNA viruses.

Carnivores and bats hold central positions for mainly sharing RNA viruses, but play only a minor role in spreading DNA viruses among humans and mammalian species. Ungulates, on the other hand, hold central positions for sharing both RNA and DNA viruses with other host species.

DNA and RNA refer to deoxyribonucleic acid and ribonucleic acid, respectively, the two crucial genetic structures encoding all living organisms. RNA viruses that cause diseases in humans and originate from animals include flu viruses, Ebola virus and the SARS virus.

The findings provide strong evidence that besides humans, domestic animals comprise the central links in networks of mammalian host-virus interactions because they share viruses with many other species and provide the pathways for future virus spread. They also carry the largest proportions of viruses known to be shared by humans and animals.

Dr Wells, who leads the Biodiversity and Health Ecology research group at Swansea University, said: “We found RNA viruses to have high potential to shift across mammalian species with very different life histories and habitats, enabling them to be shared by more host species.

“This means also more risk for humans in terms of unpredictable emergence of novel infectious diseases.”

He said domesticated animals include species from different taxonomic and functional groups of animals and are not particularly distinguished from wildlife, pointing to the fact that frequent virus acquisition and dissemination is the most plausible explanation of why humans and domestic animals intensively share viruses with many wildlife species.

“It’s a matter of contact and interaction across borders,” he said.

“Among the myriad of viruses and other pathogens present in different mammals across the globe, many of those that can jump and exploit novel host species benefit from humans and their companion animals leaving wildlife no longer alone — pathogens that benefit from increasing and novel contact opportunities among host species are the winners of intensifying land use and globalization.”

This research follows on from a previous study released earlier this year, which highlighted the need for a better understanding of the way harmful parasites can spread between animals and humans.

The study team comprised Wells; Serge Morand, from Kasetsart University in Thailand; and Maya Wardeh and Matthew Baylis, from the University of Liverpool.

Distinct spread of DNA and RNA viruses among mammals amid prominent role of domestic species
Konstans Wells, Serge Morand, Maya Wardeh, and Matthew Baylis
Global Ecology and Biogeography, 19 December 2019, https://doi.org/10.1111/geb.13045

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