Genetically Modifed Mosquitoes Battle Dengue Fever in Brazil

By Carl Engelking | July 8, 2015 3:04 pm


In the fight against disease-bearing mosquitoes, residents in the Brazilian city of Piracicaba have a new ally: mosquitoes.

A biotech company has released into the wild an army of genetically modified male mosquitoes that will never see their children. That’s because these mosquito dads pass on a gene to their offspring that causes them to die before they ever mature.

It’s a cutting-edge battle tactic that aims to reduce the population of mosquitoes that can infect people with dengue fever — and a new study finds that it’s working.

Million Mosquito March

The initiative’s primary target is Aedes aegypti, the main species of mosquito responsible for the 100 million dengue fever infections annually worldwide. Dengue fever causes severe joint pain, vomiting, and fever, and can be deadly.

To push back against this growing threat, United Kingdom-based company Oxitec breeds male mosquitoes with a kind of “kill switch:” They produce a lethal protein if they aren’t fed a special diet laced with an antibiotic.

The initial crop survives in the lab, but when they are released into the wild, the males mate with the local females, and the resulting offspring inherit the fatal gene and die in their larval stage.

Big Results

The Oxitec team has been testing their method in the Cayman Islands, Panama and Brazil, where 6 million killer mosquitoes have been released in the suburbs of Piracicaba. The method successfully reduced the mosquito population in a Brazilian suburb by 95 percent in one test trial  — far more effective than pesticides, and low enough that the disease could not cause an epidemic. The Oxitec team published results from that trial last week in PLOS Neglected Tropical Diseases.

Oxitec is hoping to do trials in the U.S. as well, but they are currently waiting for permission from the FDA. In recent years dengue fever has been on the rise in the Florida Keys. At this point, the FDA has completed its review, and will publish the results for the public to weigh in, New Scientist reports.

Gene Schemes

The downside to Oxitec’s method is that the deadly genetic effect wipes out its carriers, which means male mosquitoes need to be repeatedly introduced. On the positive side, it should allay fears that artificially engineered genes will persist in the wild.

Oxitec isn’t the only group attempting genetic modification as a way to solve mosquito-borne disease. As reported earlier this year in Discover, another team of scientists is attempting to wipe out female Anopheles mosquitoes, which transmit malaria. Another approach, the so-called CRISPR-Cas9 tool, could either be used to immunize mosquitoes against the malaria parasite or to eradicate the species as a whole. As for the ethics of these approaches, the topic deserves public scrutiny, scientists say.


Photo credit: mrfiza/Shutterstock

  • Akai Koru

    Alright I couldn’t resist

    Dr. Ian Malcolm: John, the kind of control you’re attempting simply is… it’s not possible. If there is one thing the history of evolution has taught us it’s that life will not be contained. Life breaks free, it expands to new territories and crashes through barriers, painfully, maybe even dangerously, but, uh… well, there it is.

    John Hammond: [sardonically] There it is.

    Henry Wu: You’re implying that a group composed entirely of female animals will… breed?

    Dr. Ian Malcolm: No. I’m, I’m simply saying that life, uh… finds a way.

    • Electric Bill

      I would be happy to disappoint you by reminding you that polio no longer exists on this planet except as carefully guarded samples. And many creatures we wish WOULD persist are dying off. So, no: wiping out anopheles, aedes aegypti, malaria, and dengue is not only possible, but desirable and worth working toward.

      • EquusMtn

        Agreed on the polio, same with smallpox. But — although I hate mosquitoes and disease as much as anyone, I hope we’re paying attention to the indirect effects of wiping out any species. For example, are there birds that depend on any of these mosquito species for survival?

        • Electric Bill

          Yup… it just so happens there are all kinds of surprises hidden in genetics– such as individuals that have sickle cell anemia are immune to malaria.

          Hopefully, these people have already worked out any hidden probs if mosquitos are eradicated. If there is some such issue, we should find out soon enough to alter our tactics such as keeping the mosquito population low enough to dramatically reduce dengue infections, but leave enough of them for the dependent fauna to feed on.

          Reducing the mosquito population does not have a 1 – to – one effect on dengue… if the mosquito population drops significantly, many of the mosquitos will not be dengue carriers since humans and mosquitos cross-infect.

  • Mike Richardson

    We could use a few of those genetically modified skeeters in Louisiana. Anything that lets me get outside at night with my telescope without risking West Nile virus works for me.

    • Teresa

      If you want extra profit averaging 50 dollars to 300 dollars a day for doing work over internet at your home for 3-4 hours each day then read more here…

    • Dr Janet Lee

      Malaysia too needs this.

  • Kaiden Degas

    Millennium of battle between humans and mosquitoes has finally come to a head. We win

    • Ivar Ivarson

      This one round.

      • edith_jones3
  • Ray Franklin

    How about engineering a mosquito that can produce eggs on a diet of nectar? It should out-compete the blood-suckers while preserving the ecological benefits of mosquitoes (pollination, food for birds, bats, dragonflies).

  • Herne Webber

    The last thing they mentioned was actually the star attraction – make the damnable bugs’ immune systems kill off the diseases they can carry without transmitting them. That also solves the “what if there is some animal who needs them?” and the “but their males pollinate many flowering plants” dilemmas. Personally, I would not only *not* be bothered by genetically enhanced mosquitoes like those persisting, I would *prefer* that they do!

    The first method they mentioned would, however, be a good disease prevention stop-gap, as well as an immediate solution to areas that have been taken over by foreign, invasive species of mosquitoes, such as the pictured tiger mosquito (which carries West Nile in the U.S.). Foreign, invasive species of animals essentially cause local ecosystems to become ‘sick,’ in that, such as in this case, their males will not bother to pollinate the flowers that the other five mosquitoes of East TN used to do more of. The ecosystems lose functionality right under our noses. P.S., this kind of solution would also work on other species, such as in areas with Africanised honeybees (i.e., the killer kind).



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