Nav: Home

Mosquitoes that spread Zika virus could simultaneously transmit other viruses

May 19, 2017

A new study led by Colorado State University researchers found that Aedes aegypti, the primary mosquito that carries Zika virus, might also transmit chikungunya and dengue viruses with one bite. The findings shed new light on what's known as a coinfection, which scientists said is not yet fully understood and may be fairly common in areas experiencing outbreaks.

"A mosquito, in theory, could give you multiple viruses at once," said Claudia Ruckert, post-doctoral researcher in CSU's Arthropod-borne and Infectious Diseases Laboratory.

Ruckert presented initial findings from the study last fall at the annual meeting of the American Society of Tropical Medicine & Hygiene in Atlanta, Georgia. The research team's paper was published May 19 in Nature Communications.

The CSU team infected mosquitoes in the lab with multiple kinds of viruses to learn more about the transmission of more than one infection from a single mosquito bite. While they described the lab results as surprising, researchers said there's no reason to believe that these coinfections are more severe than being infected with one virus at a time. Existing research on coinfections is sparse, and the findings are contradictory.

One, two, three viruses in one mosquito

Chikungunya, dengue and Zika viruses are transmitted to humans by Aedes aegypti mosquitoes, which live in tropical, subtropical, and in some temperate climates. As the viruses continue to emerge into new regions, the likelihood of coinfection by multiple viruses may be increasing. At the same time, the frequency of coinfection and its clinical and epidemiologic implications are poorly understood.

The first report of chikungunya and dengue virus coinfection occurred in 1967, according to the study. More recently, coinfections of Zika and dengue viruses, Zika and chikungunya, and all three viruses have been reported during various outbreaks, including the recent outbreak of Zika virus in North and South America.

Ruckert said the research team found that mosquitoes in the lab can transmit all three viruses simultaneously, although this is likely to be extremely rare in nature.

"Dual infections in humans, however, are fairly common, or more common than we would have thought," she said.

CSU researchers had expected to find that one virus would prove to be dominant and outcompete the others in the midgut of the mosquito where the infections establish and replicate before being transmitted to humans.

"It's interesting that all three replicate in a really small area in the mosquito's body," Ruckert said. "When these mosquitoes get infected with two or three different viruses, there's almost no effect that the viruses have on each other in the same mosquito."

Greg Ebel, director of the Arthropod-borne and Infectious Diseases Laboratory and co-author of the study, said the results were surprising.

"Based on what I know as a virologist, epidemiologist and entomologist, I thought that the viruses would either compete or enhance each other in some way," he said. "On the one hand, all of these viruses have mechanisms to suppress mosquito immunity, which could lead to synergy. On the other hand, they all likely require similar resources within infected cells, which could lead to competition. We didn't see much evidence of either one of these things in mosquitoes that were infected in the lab by multiple viruses."

Three viruses, similar symptoms

Zika virus typically results in symptoms similar to the flu and may be accompanied by a skin rash. Last year, however, concerns about the virus skyrocketed following the link between Zika virus infection with microcephaly in Brazil. Microcephaly is when a baby is born with a small head and incomplete brain development.

Concerns about Zika virus were also heightened following news that the virus could be transmitted sexually in addition to being spread by mosquitoes. Brian Foy, CSU associate professor in the Arthropod-borne and Infectious Diseases Laboratory, made that connection in 2008.

Dengue and chikungunya virus symptoms are similar to an infection with Zika virus, and can also include joint and bone pain, nose or gum bleeding and bruising.

No strong evidence coinfection poses serious threat to humans

What is the threat for people diagnosed with a coinfection?

"There's no strong evidence that coinfection of humans results in infections that are clinically more severe," Ruckert said.

But findings are contradictory. A team in Nicaragua looked at a large number of coinfection cases in one study, but saw no changes in hospitalization or clinical care. But other studies found a possible link between neurological complications and coinfection.

"There might be some indications, but it is still fairly unknown what the effect is from coinfection," said Ruckert.

It is also likely that coinfections in humans are significantly underdiagnosed.

"Depending on what diagnostics are used, and depending on what the clinicians think, they might not notice there's another virus," Ruckert said. "It could definitely lead to misinterpretation of disease severity."

Next steps for coinfection research

Ruckert and the team in the Ebel Lab are now taking a closer look at what happens when mosquitoes are infected with multiple viruses. They'll explore how a coinfection affects the evolution of viruses within the mosquito.

"We will study how these virus-mosquito interactions change when there are two viruses, what gets transmitted from a coinfected mosquito, and how that differs from a mosquito infected with one virus," Ruckert said.

The team is also interested in learning more about where the viruses replicate in mosquitoes, and by potentially examining yellow fever, a fourth virus that is carried by Aedes aegypti, as a possibility for coinfection with chikungunya, dengue or Zika viruses.

Yellow fever virus is found in tropical and subtropical areas in South America and Africa. The Brazilian Ministry of Health reported an ongoing outbreak in December 2016.

It is a very rare cause of illness in U.S. travelers, according to the Centers for Disease Control and Prevention. But between 20 percent and 50 percent of people who develop severe illness related to yellow fever virus may die.

"A large urban outbreak of yellow fever virus in a tropical megacity is a terrifying prospect," said Ebel.
-end-


Colorado State University

Related Mosquitoes Articles:

Mosquitoes are drawn to flowers as much as people -- and now scientists know why
Despite their reputation as blood-suckers, mosquitoes actually spent most of their time drinking nectar from flowers.
Mosquitoes engineered to repel dengue virus
An international team of scientists has synthetically engineered mosquitoes that halt the transmission of the dengue virus.
Engineered mosquitoes cannot be infected with or transmit any dengue virus
Genetically engineered mosquitoes are resistant to multiple types of dengue virus (DENV), according to a study published Jan.
Researchers identify that mosquitoes can sense toxins through their legs
Researchers at LSTM have identified a completely new mechanism by which mosquitoes that carry malaria are becoming resistant to insecticide.
Mated female mosquitoes are more likely to transmit malaria parasites
Female mosquitoes that have mated are more likely to transmit malaria parasites than virgin females, according to a study published Nov.
In Baltimore, lower income neighborhoods have bigger mosquitoes
Low-income urban neighborhoods not only have more mosquitoes, but they are larger-bodied, indicating that they could be more efficient at transmitting diseases.
Mosquitoes more likely to lay eggs in closely spaced habitats
Patches of standing water that are close together are more likely to be used by mosquitoes to lay eggs in than patches that are farther apart.
Why do mosquitoes choose us? Lindy McBride is on the case
Most of the 3,000+ mosquito species are opportunistic, but Princeton's Lindy McBride is most interested in the mosquitoes that scientists call 'disease vectors' -- carriers of diseases that plague humans -- some of which have evolved to bite humans almost exclusively.
Biting backfire: Some mosquitoes actually benefit from pesticide application
The common perception that pesticides reduce or eliminate target insect species may not always hold.
What makes mosquitoes avoid DEET? An answer in their legs
Many of us slather ourselves in DEET each summer in hopes of avoiding mosquito bites, and it generally works rather well.
More Mosquitoes News and Mosquitoes 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

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
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

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at Radiolab.org/donate.