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South Coast Researcher Leads Team Developing Cutting Edge Approach To Controlling Dangerous Mosquitoes

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(Photo courtesy James Gathany, Centers for Disease Control
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An Aedes aegypti mosquito, the type which are the focus of the research led by a UC Santa Barbara scientist.

Gene modification used to create sterile male mosquitoes

There's a pandemic that’s sweeping the world, infecting an estimated 700 million people a year annually. No, it’s not COVID-19. It’s mosquito bourne diseases. A South Coast scientist is using genetics to take on the crisis.

UC Santa Barbara professor Craig Montell led a team of researchers that’s developed a potential breakthrough in combatting one of the most dangerous species of the insects. Aedes aegypti mosquitoes are threatening to bring diseases normally found in the other parts of the world to the U.S. They are common in other parts of the world, and are an emerging threat in the United States. One of the mosquitoes was found in Santa Barbara County for the first time last year.

For more than a hundred years, insecticides have been the primary tool in controlling mosquitos. But, Montell says that approach is simply bad for the environment, because the chemicals kill other insects, like bees.

Montell says some researchers tried a different approach: using chemical, or radiation to make the A. aegypti male mosquitos sterile. He says the idea was good, but the way it was done didn’t work. The mosquitoes were sterile, but the treatment also left them unhealthy.

So, Montell and his team tried a different approach: gene editing, in effect creating genetically sterile mosquitoes.

The idea would be to grow, and release huge quantities of the sterile male mosquitoes, so the females would mate with them. If the idea of growing and releasing large quantities of male mosquitoes sounds alarming, it shouldn’t. They don’t bite humans. The females rely on human blood to support healthy eggs. It's those bites which transmit disease. A mosquito which bites someone with a disease like dengue fever or Zika virus can then carry it to the next person they bite.

For the idea to work, huge quantities of the sterile males would be needed, to insure they mate with the females. It’s a little more complicated, so we have to talk about mosquito sex. Nature has given female A. egypti mosquitos a huge drive to reproduce, which means they have a huge sex drive. The more sterile males the better, to insure that the females sex drive is quenched before they connect with a wild, fertile male.

Montell says their tests show all this works. He says the most practical place to use the high-tech mosquito control technique is in parts of the world where these mosquitoes are widespread, like South America. They aren't that widespread in the United States yet.

The UCSB researcher says they are now focusing on developing a strain of the mosquitos which are not only sterile, but in effect super stud mosquitoes wshich can increase the odds of making sure the females don't mate with wild males.

The researchers say if this approach is adopted, it could be easy to implement. Mosquito eggs are very resilient, and can be produced in labs and easily shipped around the world. The results of the study were just published in the Proceedings of the National Academy of Sciences.