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A proposal to release genetically engineered mosquitoes for the first time in the United States cleared an important threshold Saturday, with mosquito control officials in the Florida Keys giving their nod of approval to a hotly debated field trial.

The board of the Florida Keys Mosquito Control District voted 3-2 to move forward with the trial, with commissioners Stephen Smith and William Shaw opposing the measure, a spokeswoman for the mosquito control district said.

Several steps remain before the trial can commence. First, officials need to find a new site after two-thirds of voters in the proposed location — a community called Key Haven — opposed the trial when asked on a nonbinding ballot measure earlier this month if it should move forward or not.


The Food and Drug Administration will need to give the final approval once the new site is selected. The agency this summer signaled that it supported moving ahead with a trial.

Although voters in Key Haven came out against the referendum, a second referendum open to all of Monroe County, where Key Haven is located, got the support of the majority of voters.


If the trial proceeds, officials would deploy Aedes aegypti mosquitoes genetically altered by the British biotech company Oxitec. The modification is designed so that any offspring produced by the Oxitec mosquitoes and wild mosquitoes will fail to mature and reproduce, cutting the population. By wiping out Aedes aegypti mosquitoes, the technology could become a tool to fight mosquito-borne diseases including Zika, dengue, and chikungunya.

Opponents of the trial have said they don’t want their homes to become the site of an experiment run by a company. Others said they fear that it might not be safe for the environment and have raised concerns about the consequences of an altered mosquito biting a person.

Oxitec tries to release only male mosquitoes, which don’t bite, but it’s estimated that a tiny number of females do get released. But even in that case, the company says, the altered genes are not in the mosquitoes’ saliva, so wouldn’t be passed to a person via a bite.

The FDA has also concluded that a trial would neither harm the environment nor people.

In field trials in locations including Brazil and Panama, Oxitec mosquitoes have helped cut the mosquito population by up to 90 percent in the short term. The mosquitoes also slowed dengue transmission in those areas, the company says.

At the meeting Saturday, some residents continued to voice their opposition to the board commissioners. One woman said that if the commissioners chose Key Largo as the new site for the trial, residents there would hire private mosquito control crews to wipe out the modified mosquitoes.

“Have fun with that,” the woman told the board.