Study examines human impact on diversity and virulence of zoonotic parasite
A new study published in the Proceedings of the National Academy of Sciences contributes a fundamentally unique perspective on the ecology and evolution of infection diseases.
“A majority of emerging infectious diseases in humans are transmitted from animals,” says Chunlei Su, associate professor of microbiology and corresponding author of the study. “It is generally agreed that our behavior can influence our exposure to such pathogens, but little is known regarding our role in shaping evolution in such pathogens.”
One of the most widespread zoonotic pathogens known today is Toxoplasma gondii, a parasite found worldwide that is capable of infecting virtually all warm-blooded animals. It is one of the most common parasites in humans living in developed countries. Several genotypes of this parasite dominate in the northern and southern hemispheres, but it is not clear what factor(s) shape the modern-day genetic diversity and virulence of the parasite.
In the study, researchers looked at several lineages of T. gondii and discovered the rise and expansion of farming in the past 11,000 years established a specific transmission cycle for the parasite. This, in turn, played a significant role in the selection of certain lineages of T. gondii.
“Our results indicate that expansion of agriculture influenced not only the biogeography, but also the virulence of Toxoplasma gondii,” Su says. “By linking landscape ecology to parasite virulence, our framework contributes a fundamentally unique perspective on the ecology and evolution of infectious disease. These results have significant implications concerning transmission and evolution of zoonotic pathogens in the rapidly expanding anthropized environment demanded by rapid growth of the human population and intensive international trading at present and in the future.”