The Florida Keys will this week see the release of genetically-modified, non-biting male mosquito larvae as part of a controversial program designed to curb the spread of insect-borne diseases such as dengue, Zika, yellow fever and other human diseases.
The Florida Keys Mosquito Control District and British firm biotech Oxitec announced last week that 12,000 of the invasive Aedes aegypti mosquito species are expected to emerge each week for three weeks from six locations: two on Cudjoe Key, one on Ramrod Key and three on Vaca Key.
Eventually it is planned that hundreds of millions of the mosquitos might be released.
Oxitec’s non-biting male mosquitoes will mate with the local biting female mosquitoes and since the female offspring cannot themselves survive to reproduce, the population of Aedes aegypti is subsequently controlled.
According to the CDC, the genetically-modified mosquitos carry two types of genes: a fluorescent marker gene that glows under a special red light, and a self-limiting gene that prevents female mosquito offspring from surviving to adulthood.
Mosquitos at the target locations will then be monitored against untreated comparison sites as part of an Environmental Protection Agency-approved project. Oxitec says an evaluation of the project will be provided by the CDC and the University of Florida’s Medical Entomology Laboratory, among others.
According to Oxitec, Aedes aegypti makes up about 4%of the mosquito population in the Keys but is responsible for “virtually all mosquito-borne diseases transmitted to humans” and can transmit heartworm and other potentially deadly diseases to pets and animals.
“As we are seeing development of resistance to some of our current control methods, we are in need of new tools to combat this mosquito,” said Andrea Leal, executive director of the Florida Keys Mosquito Control District. “And given the unique ecosystem we live in, those tools need to be safe, environmentally friendly, and targeted.”
More than 7,300 dengue cases were reported in the US between 2010 and 2020 – cases are largely contracted outside the US, though 71 cases were transmitted in Florida, according to CDC. Over the summer of 2016, the Zika virus infected 29 people within a six-block area forcing them to aerial spray to control mosquitoes, the agency has said.
The EPA approved an experimental use permit after a risk assessment in 2019 “determined that there will be no unreasonable adverse effects to humans or the environment as a result of the experimental permit to release Oxitec’s OX5034 male mosquito”.
But a similar test in the Cayman Islands in 2016 was delayed by opponents who “argued that the government had not provided sufficient information about potential risks or adequately studied other alternatives”, reported the Associated Press.
Some environmentalists remain skeptical or outright opposed. Last year, Jaydee Hanson, policy director for the International Center for Technology Assessment and Center for Food Safety, told the Guardian the program is a “Jurassic Park experiment”.
Barry Wray, executive director of the Florida Keys Environmental Coalition added: “People here in Florida do not consent to the genetically engineered mosquitoes or to being human experiments.”
A recent report by the non-profit digital science magazine Undark noted that Oxitec had been pushing for an experimental release in the Keys but both Key Haven and Key West had rejected the proposals after critics demanded more proof that the release is necessary.
Undark drew attention to the use of tetracycline – an antibiotic without which the female mosquitoes will die in early larval stages.
The EPA assessment noted that release of modified mosquitos will not take place within “500 meters of commercial citrus growing areas or wastewater treatment sites due to considerations regarding the impact of environmental sources of tetracyclines on female OX5034 mosquito survival”.
A Yale University study that analyzed Oxitec’s Brazil release had claimed some of the offspring of the genetically modified mosquitoes had survived to adulthood, though Oxitec rejected the findings, telling Gizmodo in 2019 that the study includes “numerous false, speculative and unsubstantiated claims and statements”.