Nav: Home

Virus evolution differs by species of mosquito carrier

March 31, 2016

A new study on how the West Nile virus evolves in four species of mosquitos shows that viruses accumulate mutations in their insect carriers that reduce how well they reproduce when passed on to a bird host. Viruses carried by one of the tropical species were best able to maintain their reproductive fitness and thus spread. The study, published March 31, 2016 in Cell Host & Microbe, could lead to new strategies for predicting and preparing for future viral outbreaks.

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

Of all disease-transmitting insects, the mosquito is the greatest menace, spreading malaria, dengue, and yellow fever, which together are responsible for several million deaths and hundreds of millions of cases every year. Currently, mosquito-borne viruses such as West Nile, Chikungunya, and Zika viruses are all in various states of emergence at local or global scales. To predict and prepare for future outbreaks, it's necessary to understand the selective forces that shape virus evolution in different mosquito species and vertebrate hosts.

To address this question, Ebel and his team infected four different mosquito species with the West Nile virus and used next-generation sequencing to characterize virus populations within distinct tissues. They found that the genetic diversity of the virus population depended on the mosquito species, with the greatest accumulation of mutations occurring in the southern house mosquito, Culex quinquefasciatus.

However, the viral mutations that accumulated in all four mosquito vectors imposed a fitness trade-off in vertebrate hosts. These mutations reduced the ability of West Nile virus populations to survive in infected chicken skin cells when competing against viruses that did not undergo mosquito transmission. But West Nile virus populations from Culex quinquefasciatus fared better than virus populations from the other three mosquito species.

Taken together, the findings show that Culex quinquefasciatus may be a significant driver of West Nile virus divergence and is more likely to transmit viruses that exhibit greater fitness in avian hosts compared to other mosquito species. This information could be used to help focus ongoing surveillance strategies and outbreak prediction efforts with an eye toward the emergence of new virus genotypes that could alter transmission patterns.

"Based on our work, you could make predictions about what kinds of ecologies might lead to West Nile virus that is more or less fit, and where novel genotypes might come from," Ebel says. "For example, most of the new US West Nile virus genotypes seem to have originated in the southern US. Our data on mosquitoes fit with this because Cx. quinquefasciatus are found in the south, and also seem to be more likely to generate new West Nile virus genotypes compared to more northern species."

The researchers plan to further explore the underlying evolutionary mechanisms at play and determine whether similar findings hold for the Zika virus. "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 says. "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."
The authors are supported by the National Institutes of Health.

Cell Host & Microbe, Grubaugh et al.: "Genetic Drift during Systemic Arbovirus Infection of Mosquito Vectors Leads to Decreased Relative Fitness during Host Switching"

Cell Host & Microbe (@cellhostmicrobe), published by Cell Press, is a monthly journal that publishes novel findings and translational studies related to microbes (which include bacteria, fungi, parasites, and viruses). The unifying theme is the integrated study of microbes in conjunction and communication with each other, their host, and the cellular environment they inhabit. For more information, please visit To receive Cell Press media alerts, contact

Cell Press

Related West Nile Virus Articles:

West Nile virus triggers brain inflammation by inhibiting protein degradation
West Nile virus (WNV) inhibits autophagy -- an essential system that digests or removes cellular constituents such as proteins -- to induce the aggregation of proteins in infected cells, triggering cell death and brain inflammation (encephalitis), according to Hokkaido University researchers.
WSU study shows insulin can increase mosquitoes' immunity to West Nile virus
A discovery by a Washington State University-led research team has the potential to inhibit the spread of West Nile virus as well as Zika and dengue viruses.
Critical protein that could unlock West Nile/Zika virus treatments identified
A team of Georgia State scientists has identified a protein that is critical in controlling replication of West Nile and Zika viruses -- and could be important for developing therapies to prevent and treat those viruses.
West Nile virus in the New World: Reflections on 20 years in pursuit of an elusive foe
Though eradication of West Nile virus remains beyond our capability, the body of knowledge built since its arrival in the Americas in 1999 is now powering efforts to minimize its impact and prepare for the invasion of other mosquito-borne diseases.
Light pollution may be increasing West Nile virus spillover from wild birds
House sparrows infected with West Nile virus (WNV) that live in light polluted conditions remain infectious for two days longer than those who do not, increasing the potential for a WNV outbreak by about 41%.
Mount Sinai researchers find significant delays in West Nile virus reporting
Mount Sinai researchers found significant delays in reporting human cases of West Nile virus, hampering real-time forecasting of the potentially deadly mosquito-borne disease, according to a study in the JAMA Network Open in April.
Insecticide resistance genes affect vector competence for West Nile virus
In a context of overuse of insecticides, which leads to the selection of resistant mosquitoes, it is already known that this resistance to insecticides affects interactions between mosquitoes and the pathogens they transmit.
Where will the world's next Zika, West Nile or Dengue virus come from?
Scientists from the University of California, Davis, have identified wildlife species that are the most likely to host flaviviruses such as Zika, West Nile, dengue and yellow fever.
Vanderbilt discovery could neutralize West Nile virus
Researchers at Vanderbilt University Medical Center and colleagues have isolated a human monoclonal antibody that can 'neutralize' the West Nile virus and potentially prevent a leading cause of viral encephalitis (brain inflammation) in the United States.
Researchers develop a novel RNA-based therapy to target West Nile virus
A Yale-led research team developed a new RNA therapy, delivered through the nose, to treat mice infected with West Nile Virus.
More West Nile Virus News and West Nile Virus Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at