In 2018, Oxitec’s proposal to test the release of biologically modified mosquitoes to combat biting invasive populations was bandied back and forth between the Environmental Protection Agency and Food and Drug Administration. The proposal drew much comment, plus there was a presidential election, and new department heads appointed. In the midst of all that turmoil, Oxitec — a U.S.-owned, U.K.-based company that develops biologically engineered solutions to control disease-transmitting insects — withdrew its application.

Not because it thinks it doesn’t have promise, but because Oxitec says it has something better to offer. The EPA’s public comment on its 2nd Generation trial opened on the federal register on Sept. 11. (Visit and search for “Oxitec.”)

“The 2nd Generation mosquito is just as environmentally friendly and safe, but with the potential for greater performance and overall cost effectiveness,” said Kelly Matzen, who heads research and development for Oxitec.

Here are the key points.

  • Only males

The eggs of the 2nd Generation mosquito produce ONLY males. Male mosquitoes don’t bite and are therefore incapable of spreading diseases such as dengue, Zika, chikungunya and yellow fever. According to Oxitec, its Aedes aegypti carry a self-limiting gene that prevents female offspring from surviving, allowing for male-only production. The previous proposed method required adult mosquitoes to be carefully sorted by gender.

  • Eggs, not adults

Instead of raising modified mosquitoes to adulthood before releasing them into the wild, the 2nd Generation mosquitoes can be distributed as eggs in boxes. (The eggs are currently produced in the U.K. and shipped globally to places such as Brazil where a trial is underway.) A box containing eggs could be placed in a back yard and filled with water, after which the males hatch and start to grow. When the mosquitoes emerge, they fly away into the neighborhood to find female mosquitoes to mate with. The previous proposed method required adult mosquitoes to be raised near the test site and then released via the use of a specially equipped van.

  • Still self-limiting, but better

With the 1st Generation of the Oxitec mosquito, released males mated with a female in the wild, and all of the offspring — male and female — would die. With the 2nd Generation, it just targets the females. Male progeny survive, also carrying the self-limiting gene to half its offspring that are male only … and so on. The 2nd Generation technology allows Oxitec to reduce the number of times the egg box must be refilled, reduces the total population, and Oxitec says, when releases stop, the 2nd Generation mosquito dies out in the wild after a few generations.

  • Tetracycline

And, finally, Oxitec said the 2nd Generation mosquitoes it plans to release do not come into contact with tetracycline at any stage, either as eggs or as adults.

The 2nd Generation mosquito has many advantages, said Kevin Gorman, who heads Oxitec’s field operations.

“It’s easier to use and a way to get the tools to fight Aedes aegypti into the hands of many,” he said.

Phil Goodman is the chairman of the board of the Florida Keys Mosquito Control District. He’s said the 2nd Generation technology overcomes many hurdles its predecessor didn’t including, potentially, the cost.

“The EPA doesn’t allow any talk of commercialization during the comment period,” Goodman said, “so we don’t have any projections. But if we can shorten the route to production and make it simpler, that has to have an impact on the cost down the road. I mean, if Oxitec ships eggs instead of adult mosquitoes … well, they could probably fit one million genetically modified mosquitoes in something the size of a shoebox. This could make distribution a lot more effective.”

The EPA has announced a 30-day public consultation, during which residents in the Florida Keys and elsewhere can share their views on the project with the EPA.

Should approval be granted, locations for the trials in the Keys would be a joint decision between Oxitec and the Florida Keys Mosquito Control District. This is of particular relevance since the Key Haven neighborhood rejected a genetically modified mosquito release in its neighborhood in a non-binding referendum question in the 2016 general election. Precinct 11 voted 65% against the study. But in a second referendum question, for the entire county, 31 of 33 precincts approved an “effectiveness trial in Monroe County” of genetically modified mosquitoes. In Ocean Reef, 84% of voters approved of a test and in Grassy Key, 72% of voters approved of a test.

Oxitec’s 1st Generation mosquito proposal met with public resistance in the Keys. Dr. John W. Norris of Key West has opposed the technology, citing the possible creation of an antibiotic-resistant scenario that could pose a health threat to humans. Proponents of the technology welcome a way to fight vector diseases (transmitted through the bite of infected insects) such as dengue, Zika, yellow fever and chikungunya. Local veterinarian Dr. Doug Mader said he supported the 1st Generation technology 100%, as it would have reduced the number of canine heartworm infections — he said he sees four or five a month in the Keys — also a mosquito-borne disease.

Oxitec reports it has positive regulatory findings from independent scientific reviews and regulators from around the world. Their mosquitoes have been determined by multiple regulatory agencies, including the U.S. FDA and Brazil’s CTNBio, to be safe, and to pose no threat to humans, animals or the environment.

Join Our Blast – Keys News Right to Your INBOX


  1. Anybody who states the tetracycline is not a factor in what oxitec plans when they release their insects on our islands is a fraud.

    The boards audio is poor but the oxitec rep tells the Florida Keys Mosquito Board that version 2 needs 10 times the tetracycline to breed.  Telling people the males are not ‘reared’ in tetracycline but leaving out they are ‘bred’ with 10x tetracycline is grossly unethical.  Ethics don’t seem to be an issue for some board members. Version 1 was riddled with scientific concerns.  Tetracycline was the most pronounced.  Caymans dropped it.  Brazil has gene transfer findings of which are published in the prestigious journal Nature yesterday.  

    Cayman scientists said there were ‘mold’ issues with version 1.  Antibiotics in human cause yeast (mold type) infections. Guess they do in gm mosquitoes too. Cayman scientists were not comfortable saying version 1 was successful at all. I have emails showing the government engaged in the issue until they were to have the data. The project was halted then and they then denied their own data. I would offer those emails for public review.

    Why is this continuing without even meeting a testing petition from Florida Keys release area physicians?  FDA got the petition and sent the entire issue to the EPA. EPA asked for the scientific concerns at a meeting in Washington DC. Barry Wray and I gave them the science. The ‘mandatory’ July 2018 approval date came and went. Commissioner Goodman stated only a serious concern could block the July approval. Guess they got a serious concern.  

    Now mosquito control focuses on Star Wars projects like gm mosquitoes and not following guidelines for basic mosquito disease control. Locals are turning up with past positive West Nile tests. None this year so far are infected now. Mosquito control ignores CDC testing guidelines and leaves us to wait for virus infected humans.   

    Watch the video on version 2 presented by Oxitec to our mosquito control board at and especially listen to minute 29.  

    Tetracycline is now joined by the scientifically valid significant concern of gene transfer. This from a leadership waiting for sick humans?  Test the bugs please.

    Judge for yourself.


    Minute 29 address the tetracycline need of ‘ version 2’ females. They are antibiotic dependent for breeding. If the eggs come out of mom, how do they sterile the birth of those eggs. Mom shares antibiotic richly altered bacteria with the eggs. How do you sterilize an egg without killing the occupant? Especially by the 10s of thousands

  3. Sara, perhaps you would like to actually present the other side of the discussion a little more completely, to inform our community of something other than Oxitec’s marking message?

    Here are links to why Oxitec mosquitoes are unacceptable in the Keys. Keep in mind that Oxitec still promotes that they suppressed populations in Cayman and Brazil by over 90%, but the Chief Scientist, Alan Wheeler, in Cayman feels that his team could not even support 62% suppression being published, but it already had, so they didn’t retract it. Brazil disputed as well and independent evaluations suggested in the 60 – 70% ranges. So yes, there are both credibility and scientific analytical concerns evident with Oxitec.

    This week, published study that shows what we predicted and Oxitec denied repeatedly, that the OX513A could establish hybrid colonies in the wild. Imagine if that had happened here? If not for the will of many who objected, this would have happened in the FL Keys National Marine Sanctuary, where eco-tourist come to observe nature and spend money. Really? What would that do for our economy? Would mothers and fathers wish to bring their children to a place where uncharacterized, manmade, mutant mosquitoes could bite them?

    Here are emails from the Chief Scientist in the Cayman MRCU. I’m sure Oxitec Snake Oil Sales Department can put some spin on these as well. They are unvarnished and will never be pretty, no matter what the marketing is from Oxitec.

    Our problem in the Keys remains, that 3 of our FK Mosquito Control District Commissioners have voted in block step, consistently, to support this project, in the face of all the failures and scientific concerns, not the least of which is antibiotic resistant bacteria; a problem that looms much larger than the viruses that the Aedes Aegypti mosquito present. They have put our ecosystem and public health at risk and this should be unacceptable for people that are in position to protect it! Maybe they will realize they have not done well by our community and step aside, which would be a service to our community and more honorable than trying to defend incompetence.

    We have other solutions that work more effectively than Oxitec’s methods, they are natural, have been trialed here in the Keys providing very effective suppression, there are version for both the Aedes Aegypti and the Albopictus, another Keys mosquito that transmits these viruses of concern, have received limited, but soon to be comprehensive permits for commercial use by the EPA and the FKMCD could have expanded these programs already and have not. If they were so focused on protecting our health, why wouldn’t they be expanding the effective use of Wolbachia, a harmless bacteria to humans, further?

    If you wish to make comments to the EPA, please do. They will weigh thoughtful detail, scientific comments most heavily, but it is important for people to have a voice. on or before Oct. 11, 2019.

    The referendum in 2016, other than the educated community of Key Haven, was an example of what over $2M in marketing from Oxitec can buy, versus the unfunded aware and passionate people within our community were able to do over a 6 week period for outreach and education. The FKMCD did not wish to have an actual informed referendum, where the community truly has the entire story. Future referendums would be able to include Oxitec’s now clear history of polluting Brazil with uncharacterized, unintended manmade genetic mutations that exist in wild mosquito colonies.

    15 years Oxitec has had these mosquitoes and has never ran a clinical trial on the bite reaction on humans. Feeling better about wild mutant mosquitoes now?

    Join us on facebook to continue the discussion:

    Barry Wray
    Executive Director
    Florida Keys Environmental Coalition

Comments are closed.