The first US field test of genetically modified mosquitoes for population control has begun in Florida. Approximately 144,000 mosquitoes engineered by the UK-based biotech firm Oxitec are to be expected to be set free over the next three months, the first of up to 750 million approved for release over the next two years by the US Environmental Protection Agency.

The trial aims to test whether the mosquitoes are effective at reducing populations of invasive Aedes aegypti, a species that can transmit dangerous diseases to people. The Florida Keys Mosquito Control District, which has partnered with Oxitec, has said this species makes up only 4 percent of the mosquito community in the Keys but is responsible for nearly all disease transmission and has become increasingly resistant to available pesticides, Nature reports. 

According to Oxitec, the modified mosquitoes are all male and carry a gene that makes female mosquitoes dependent on an antibiotic not available in the animals’ environment, thereby killing all of the male’s female offspring. Adult mosquitoes only live for a few weeks, and just the females bite, so the firm expects its modified males can spread the female-killing insert through the population and drastically reduce the number of potential disease vectors in the region. If successful, the mosquitoes could be used in place of pesticides in control efforts. 

A small but vocal group of Florida residents that has opposed the “mutant mosquitoes” from the get-go are continuing to seek legal action to stop it, CNN reports. Key Largo resident Mara Daly tells CNN she hopes “civil unrest happens,” and suggests residents could have their communities sprayed with pesticides in an effort to “opt out” of the trial.

Oxitec maintains that the mosquitoes have been thoroughly tested and that the company’s non-US field trials have gone well. “We have released over a billion of our mosquitoes over the years. There is no potential for risk to the environment or humans,” Kevin Gorman, one of the firm’s scientists, told the Associated Press in August 2020 when the trial was formally approved by local officials. 

According to Nature, Oxitec is not disclosing the exact locations of the releases, which are on private, fenced properties, as a deterrent against vandalism.