Genetically modified mosquitoes could be tested in California soon

The EPA also OK’d a Florida project for more trials. Now both states will decide next steps

image of a person pouring water to a blue mosquito egg-rearing box with the oxitec logo on it

A worker adds water to a mosquito egg-rearing box, a step in raising male Aedes aegypti that are engineered to sabotage mosquito reproduction in the wild.


Genetically modified mosquitoes might soon be whining on both U.S. coasts. The U.S. Environmental Protection Agency has approved two more years of testing Oxitec’s genetically modified mosquitoes as living pest controls, continuing a pilot program started in 2021 in the Florida Keys and expanding it to up to four counties in California.

Now the Florida and California state governments will consider whether to grant permission.

The male mosquitoes, OX5034 Aedes aegypti engineered by the biotech company Oxitec, carry daughter-killing genes that get passed generation to generation. When these males mate with local females outside a lab, only the sons should survive. Those inheriting the sabotage gene will grow up to mate with normal females, dooming their daughters too.

The wild A. aegypti species, an invader in North America, can spread dengue, Zika, yellow fever and other diseases (SN: 7/29/16). California first reported the invader in 2013, and by February 2022 had found it in 22 counties. The EPA permission, issued March 7, will now allow testing of the GM mosquitoes, if desired, in Stanislaus, Fresno, Tulare and San Bernadino counties.

In Florida, the permit covers just one county, Monroe, which stretches down the Keys. The 2021 mosquito releases there came after more than a decade of heated debate (SN: 5/14/21). Despite approval of the previous tests, the Florida Department of Agriculture and Consumer Services needs to vote again on the new plans. The last time, the group voted at its next board meeting after EPA announced its decision, but “we are not sure that will happen this time around,” says Chad Huff of the Florida Keys Mosquito Control District.

If approved and fulfilled to the EPA-set limits in both locations, nearly 2.5 billion of these GM mosquitoes could be released before permission expires April 30, 2024. Fortunately, male mosquitoes, GM or otherwise, don’t bite.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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