Several factors characteristic of the modern human lifestyle are reportedly responsible for the "perfect storm" that fosters the growth and transmission of diseases like COVID-19, a new study suggests.
A researcher from the University of East Anglia in England describes in a new editorial article how factors like population, pets, and domesticated livestock have all contributed to an ideal breeding ground for infectious diseases that led to zoonotic diseases - those transmitted between animals and humans. Professor Cock Van Oosterhout from the School of Environmental Sciences at UEA published the article "Mitigating the threat of emerging infectious diseases; a coevolutionary perspective" at the journal Virulence, May 7.
SYDNEY, AUSTRALIA - MAY 07: Nurse Emeldah Mufara speaks to Margaret Donnellan before administering the AstraZeneca vaccine at the Sydney West COVID Vaccine Centre on May 07, 2021, in Sydney, Australia. People over 50 are now eligible to receive the AstraZeneca COVID-19 vaccine across Australia after the federal government brought forward the start of the 2a phase of Australia's vaccine rollout to begin from Monday, 3 May.
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An Unsustainable Lifestyle Coming Home to Roost
"We humans have been living in a non-sustainable way over the past few centuries," Van Oosterhout said in a UEA release. "We now have a vast population size-not only of humans but also of domesticated animals and livestock."
He adds that these conditions create "an ideal breeding ground for the evolution and transmission of zoonotic infectious diseases that jump from an animal to a human host." In his article, the UEA professor demonstrates how the current biomass of livestock we have today is 10 times greater than all wildlife on the planet combined.
In his article, he explains the concept of genetic effective size, which determines the volume of genetic variation that can be maintained in any given population. This genetic variation is a critical factor in countering the development of potentially infectious diseases. However, the existing genetic effect size for the world's livestock is eighty times lower than the minimum viable population size required for free-living species.
"The combination of high livestock biomass and low genetic variation has tipped the co-evolutionary balance with zoonotic pathogens," Van Oosterhout also added. He noted that factors including habitat destruction, illegal wildlife trade, and other anthropogenic activities are responsible for bringing different species into contact with each other, which leads to a "spill-over, spillback, and hybridisation of the pathogens."
He adds that since mankind is in close contact with their livestock and domesticated animals, there are more chances for this spill-over of pathogens from animals into humans and the spillback from humans back to animals.
"Altogether, these conditions have created a perfect storm for the evolution and transmission of zoonotic infectious diseases," Van Oosterhout noted.
The Case of COVID-19
"COVID-19 has shown us that humans are not immune to the evolutionary processes that drive the adaptations of pathogens," the published editorial added.
He then emphasized the urgency of resetting the co-evolutionary imbalance and controlling "the transmission of pathogens" like SARS-CoV-2, the coronavirus that causes COVID-19. Van Oosterhout adds that this is possible with the use of vaccination passports, maximizing the genetic variation in livestock, and reducing mankind's consumption of animal protein.
"We also need to be aware of pathogen reservoirs, both locally and globally," the article noted.
Commenting on the urgency of the matter, Van Oosterhout said that mankind faces a "significant threat" and that the changes noted in his paper have to be implemented globally in order to "effectively combat pandemics."
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