Florida releases genetically modified mosquitoes to reduce spread of disease

A pilot program intended to reduce the spread of deadly diseases such as dengue, yellow fever and the Zika virus

Reuters May 16, 2021
A sign is seen outside a Florida Keys Mosquito Control District branch in Key Largo, Florida, U.S. May 4, 2021. PHOTO: REUTERS

Genetically modified mosquitoes have been released for the first time in the United States, taking flight in the Florida Keys in a pilot program intended to reduce the spread of deadly diseases such as dengue, yellow fever and the Zika virus.

After an odyssey spanning more than a decade to secure regulatory approval, British-based biotechnology firm Oxitec, along with the Florida Keys Mosquito Control District (FKMCD)launched the project in hope of reducing the Aedes aegypti species that spread the diseases.

While Oxitec and local authorities have high hopes for the program, local residents and environmental groups worry that not enough is known about the long-term effects of the new technology.

Nevertheless, the Environmental Protection Agency granted an experimental use permit (EUP) to Oxitecon May 1.

A half-dozen boxes containing the OX5034 mosquito created by Oxitec have been deployed in the Florida Keys, an archipelago stretching 120 miles (195 km) off the southern tip of the state.

Only female Aedes aegypti bite and spread disease, so Oxitec has created males that pass on a gene that kills female offspring before they mature. Their male offspring then continue mating and passing on the altered gene.

Meredith Fensom, Oxitec's head of global public affairs, explained how the boxes work.

"Inside we have a small container, and this is what we put the mosquito eggs in. We also have a small container for food. We leave it open. And then we fill the box, less than halfway full, with water. We close the lid, and after a week or two, our non-biting male mosquitoes begin to emerge," she said.

The company says similar projects have had over a 90 percent success rate in Brazil, Panama, the Cayman Islands and Malaysia.

Some 12,000 mosquitoes will be released in the initial stage, but later this year tens of millions of genetically modified Aedes aegypti will fan out across the region.

The mosquitoes have also been designed to emit a fluorescent glow, so that when they are captured, they can be more easily identified and studied.

"That's how we monitor for the project before, during and after to understand the mosquito population," said Fensom.

The project got a boost in 2016, when it was approved in a referendum in the Keys, despite opposition from some residents.

FKMCD Executive Director Andrea Leal says she understands community concerns but that traditional methods like fumigation from trucks and helicopters have become increasingly ineffective.

"We are seeing resistance in some of our current control methods, which has made our job at Mosquito Control that much harder," said Leal at FKMCD headquarters in Marathon, Florida.

"We're looking to integrate whatever we can into our current control methods just to make sure that we can suppress that population below disease transmission thresholds."


The authorities first turned to Oxitec after a dengue fever outbreak slammed Key West in 2009 and 2010, USA Today reported.

But environmentalists like Barry Wray, who heads the Florida Keys Environmental Coalition, are not persuaded by the long regulatory approval process.

He says it was haphazard and leaves too many questions unanswered. "You're going to risk our community, you're going to ask the people in our community to be sacrificial lambs, really."

There also have been concerns that because the genetically altered females are originally exposed to the antibiotic tetracycline, it could indirectly increase the chances of antibiotic-resistant infections in humans, USA Today reported.

But local residents like veterinary scientist Doug Mader says the science is sound.

"There haven't been any side effects to the environment or people reported. So to say that we can't use GMOs is like saying: 'Hey, let's not vaccinate for Covid,'" said Mader.

Leal says that while the Aedes aegypti are responsible for almost all mosquito-borne disease transmission, they make up only 4 percent of the total population.

"We have over 45 species in the Florida Keys. This particular mosquito is an invasive mosquito, it's not from here…So, it's not part of our natural ecosystem," she said.

If the Florida Keys project succeeds, Oxitec plans to submit the results to the EPA so that the program can be applied in other parts of the United States, the journal Nature reported.

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