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EPA OKs plan to release 2.4 million more genetically modified mosquitoes

Following Oxitec's 2021 release of 144,000 mosquitoes in the Florida Keys, the EPA approved an expanded plan that added sites in California.
Aedes aegypti mosquitoes
A lab technician displays Aedes aegypti mosquitoes infected with Wolbachia bacteria in a test tube for a photograph at the Oswaldo Cruz Foundation in Rio de Janeiro on Feb. 19, 2016.Dado Galdieri / Bloomberg via Getty Images file

A British biotech firm this week got the green light from U.S. regulators to release over 2 million genetically modified mosquitoes in Florida and California as part of an expanded effort to combat transmission of diseases like Zika, dengue fever and canine heartworm.

The experimental public health effort, which still requires final approval from state regulators, follows the 2021 release of 144,000 genetically modified mosquitoes in the Florida Keys by British biotech firm Oxitec.

Oxitec said its genetically modified male, and thus non-biting, mosquitoes "find and mate with invasive female Aedes aegypti mosquitoes, mediating a reduction of the target population as the female offspring of these encounters cannot survive," thus reducing the overall population.

In a news release announcing approval from the Environmental Protection Agency, Oxitec described its release in Florida in 2021 as a "success."

"Given the growing health threat this mosquito poses across the U.S., we’re working to make this technology available and accessible," Grey Frandsen, CEO of Oxitec said, adding that the company will now apply for approval from California and Florida regulators.

In Florida, Aedes aegypti are relatively rare but account for the vast majority of mosquito-transmitted disease, Oxitec said. The invasive species was first detected in California in 2013.

“We made significant progress during the pilot project last year, we look forward to continuing this important work during this year’s mosquito season," Andrea Leal, director of the Florida Keys Mosquito Control District, said in the Oxitec news release.

Oxitec's head of global public affairs Meredith Fensom
Oxitec's head of global public affairs Meredith Fensom speaks with Josh Gratton about the genetically engineered Aedes aegypti mosquitoes released on Jun. 9, 2021 in Marathon, Florida.Joe Raedle / Getty Images file

In its letter approving Oxitec's plan, the EPA approved the release of up to 2.4 million of the genetically modified adult male mosquitoes and eggs in Monroe County, Florida; and Stanislaus, Fresno, Tulare, and San Bernardino counties in California.

They said Oxitec's mosquito release — which the EPA calls an "experimental pesticide product" — can take place in a 34,760-acre area across the two states between now and April 30, 2024, when the experiment ends.

The EPA restricted mosquito releases from the immediate vicinity of livestock and agricultural facilities.

The approval also contains instructions for what to do in the event of a tropical storm or wildfire, natural disasters that repeatedly struck Florida and California, respectively, in recent years.

"Oxitec will return Mosquito Rearing Boxes to a secure facility safely under triple containment (with two of the three containment layers being shatterproof) before the disaster is predicted to reach the trial area, if safe to do so," the EPA said.

Even before the 2021 test of genetically modified mosquitoes, Florida officials tried other novel methods to kill growing populations of Aedes aegypti.

One program released male mosquitoes carrying a bacteria called Wolbachia, which rendered their offspring nonviable, in Key West in 2017 and Miami in 2018.

Key West first eyed using genetically modified mosquitoes a decade ago because of an outbreak of dengue fever.

Since then, the threat posed by the Aedes aegypti has grown as the invasive mosquito's range expands in the U.S.

Oxitec said in 2020 an experiment in a dengue-stricken Brazilian city resulted in 95 percent reduction in Aedes aegypti populations.