More than 20 million genetically modified mosquitoes are coming to the Florida Keys this year, in a landmark project by British biotech company Oxitec and Monroe County’s Mosquito Control District.

This mosquito control method hasn’t been used in the U.S. before. It’s a pilot program and the first trial began over the past week.

The project is aimed at reducing the population of the invasive Aedes aegypti, which carries diseases like Zika. This is the first time in the country that the U.S. Environmental Protection Agency has issued the “experimental use permit” for this method.

Andrea Leal, the Florida Keys Mosquito Control District’s executive director, said they’re watching their “tool box” shrink because of the bugs’ resistance to insecticides. The Keys had a dengue outbreak last year, the first since 2010. That’s when Mosquito Control began working with Oxitec.

“Dengue was something we worried about in other areas,” Leal said. “Once that came to our doorstep we’ve seen other diseases. Dengue for us last year and Zika in Miami-Dade. This is really why we’re looking at these new tools for mosquito control.”

Here are some questions and answers about the GMO mosquito project in the Keys:

Question: What are GMO mosquitoes?

Answer: Genetically modified mosquitoes, in this case the non-biting male Aedes aegypti species, are created in a lab by the British biotech company Oxitec. Once released, they are supposed to mate with naturally occurring females in the wild. A “self-limiting” gene prevents biting female offspring from surviving.

Q: What will the mosquitoes do?

The GMO male mosquitoes are supposed to reduce or control the population of the troublesome Aedes aegypti species, according to Oxitec and the Florida Keys Mosquito Control District.

They’ll do this by mating. But their female offspring won’t survive, Oxitec says.

A “death mechanism” designed into the mosquitoes is meant to ensure no viable female offspring will result from the mating, Oxitec says. The male offspring will pass on the “self-limiting gene” to half of their offspring. Female mosquitoes are the only ones that bite and feed off humans.

During the project’s first trial, once the male and female eggs in the boxes hatch, the females will die.

“The males will survive,” said Nathan Rose, Oxitec’s head of regulatory affairs. “They carry the gene but it doesn’t kill them. They can go pass on their genes. Only the female offspring will die.”

The Aedes aegypti mosquito makes up 4% of the mosquito population in the Keys. But it is responsible for virtually all of disease-spreading, according to the Mosquito Control District.

Q: Where are the mosquitoes being released?

A: So far, boxes with eggs, food and water have been placed in six locations — all private residences — in the Lower and Middle Keys. Two are on Cudjoe Key, one on Ramrod Key and three on Vaca Key.

Throughout those locations, about 12,000 mosquitoes will emerge each week for about 12 weeks, Oxitec says.

Q: Has this been done before?

A: Not in the U.S. when it comes to mosquitoes.

This is the first time the U.S. Environmental Protection Agency has issued an “experimental use permit” for this particular method of mosquito control.

But the technology was done in Sao Paulo, Brazil, in 2019. Oxitec called it a success, reporting that in 13 weeks, the treatment suppressed up to 95% of Aedes aegypti.

However, those figures may have been inflated. Emails obtained by an activist group revealed that the majority of one government paper that touted a 62% suppression rate was written by Oxitec.

Oxitec has used identical technology in the U.S. for pink bollworm and the diamondback moth, which are crop pests.

Q: How long will the GMO mosquito trial last? What's next?

The first trial, which began the week of April 26, will last about 12 weeks, Oxitec says. A second phase will release roughly 20 million mosquitoes.

The mosquito releases are anticipated to be completed within a single mosquito season — by the end of the year, Oxitec says. The second phase will likely not start before the middle of June but may be later.

Q: Are there any health risks to humans?

A: Oxitec says there are no heath risks.

“Oxitec mosquitoes have been determined to be safe and to pose no threat to humans or the environment by multiple regulatory agencies, including both the EPA and the FDA in the U.S., as well as in Brazil where we have conducted numerous successful field demonstrations,” said Meredith Fensom, the company’s head of global public affairs.

Oxitec’s male mosquitoes do not bite, and they will have no impact on homes or properties, she said. “As our mosquitoes are safe, non-toxic, nonallergenic, non-biting, and self-limiting, there is no risk posed by them.”

A segment of Keys residents don’t buy the company line. They say there are too many questions about how the mosquito release will affect the environment.

But the U.S. Environmental Protection Agency last year approved Oxitec to move forward with the project in Florida through 2022. The Florida Department of Agriculture and Consumer Services approved the Keys trial in June.

The Florida Keys Mosquito Control District’s five-member elected board approved the trial in August on a 4-1 vote. A majority of board members said conventional methods of targeting Aedes aegypti were progressively becoming less effective.

Q: Are there Zika or dengue issues in the Keys?

The Keys have had issues with mosquito-borne disease.

Aedes aegypti mosquitoes carry and spread Zika, yellow fever and chikungunya. The Florida Keys have had locally transmitted cases of dengue and travel-related cases of Zika in recent years.

“Mosquito control authorities work hard to reduce the Aedes aegypti mosquito,” said Meredith Fensom, Oxitec’s head of global public affairs.. “However, this species is difficult to control with current tools available, so authorities are looking for novel, safe and effective ways to keep mosquito populations at low levels.”

The Keys had a dengue outbreak last year, the first since 2010.

Q: Will traditional mosquito control continue?

A: Even with the trial, regular mosquito combat goes on.

“Normal mosquito control operations will continue,” said Andrea Leal, executive director of the Florida Keys Mosquito Control District. “What we anticipate is if we are seeing Aedes aegypti population numbers declining that we wouldn’t have to use specific control measures for Aedes aegypti.”

Q: Where do i go if I have more questions?

Go to to learn more about the project. You can also email or or call 888-308-1859. Oxitec has hosted 13 webinars on the project and they are available on the company’s website.


©2021 Miami Herald. Visit at Distributed by Tribune Content Agency, LLC.

Copyright 2021 Tribune Content Agency.