Virus evolution changes depending on species of mosquito carrier

FORT COLLINS, Colo., March 31 (UPI) -- How resilient a virus is when it finds a new host depends on the species of mosquito that carries it.

While studying the evolution of the West Nile virus in four different species of mosquitos, researchers identified a succession of accumulated mutations. These mutations inhibited the ability of the virus to reproduce once transitioned from mosquito to bird.

One of the four species, however, allowed the virus to maintain its reproductive fitness and proliferate once it infected the bird.

"Arthropod-borne viruses are some of the most difficult and persistent problems in public health. They've been burdening humanity for a very long time and continue to do so today," Gregory Ebel, a researcher at Colorado State University, explained in a news release.

Ebel is the senior author of a new paper on the subject, published this week in the journal Cell Host and Microbe.

"Our study is significant because we identified one mosquito species that seems to be most important in generating new virus variants," Ebel said. "This adds to the body of evidence that different mosquitoes and birds can have very different impacts on RNA virus evolution."

Established mosquito-borne diseases malaria, dengue and yellow fever infect millions every year. Meanwhile, West Nile, Chikungunya and Zika viruses are emerging as new threats to human health. Understanding how these viruses spread is key to combating infections and preparing for the impacts on human health.

Genetic mutations aren't all bad. They're provide genetic diversity, which is key to the survival of these viruses. As the viruses accumulate essential diversity, however, they sacrifice reproductive ability.

This trade-off was less apparent in the southern house mosquito, Culex quinquefasciatus. Not only did West Nile virus carried by the species acquire more mutations, it also fared better once transported to chicken skin cells.

The research suggests the southern house mosquito is key driver of the evolution and spread of West Nile virus. Edel says the lab work feats neatly with the rate of infections and viral evolution being seen in the American South were the species is prevalent.

"This is important because when outbreaks of arboviruses occur, as is happening with Zika right now, there are tremendous opportunities for the virus to undergo evolutionary change in order to maximize transmission potential," Ebel said. "Notably, this has happened recently with Chikungunya and West Nile virus. It doesn't seem like a stretch to think that it could happen with Zika, too."