Florida Will Release 750 Genetically Modified Mosquitoes to Stop Disease Spread

In an effort to fight the spread of viral mosquito-borne illnesses, the Florida Keys Mosquito Control District Board of Commissioners has approved the release of 750 million genetically modified (GMO) mosquitoes starting in 2021. The five-member board made their decision on August 18. This will be the first public trial of GMO mosquitoes in the U.S.

The mosquitoes, developed by the British biotechnology group Oxitec, belong to the Aedes aegypti species—the same invasive species known to spread viral illnesses such as Zika and Dengue fever. By creating genetically modified males to mate with non-genetically modified females, scientists plan to breed offspring that die quickly.

The hope is to prevent the spread of Dengue fever, a painful virus acquired only by mosquito bite which made a reappearance in the Florida Keys in 2009. Twenty-two cases were reported that year, despite the last case being reported in 1934. According to the Florida Department of Health, a small number of people now become infected in the state each year.

How Will This Work?

Experts say the key to reducing the population of Aedes aegypti mosquitoes is preventing female mosquitoes from maturing.

Luca Facchinelli, PhD, a medical entomologist specializing in mosquito ecology and behavior, tells Verywell that the GMO mosquitoes will be males intended to mate with wild female mosquitoes of the same species.

These male mosquitoes will be genetically modified so their female offspring will die before reaching adulthood, leaving only male mosquitoes to grow to maturity, he adds.

“The number of females in the population will decline and the probability of arbovirus transmission in the area will decrease accordingly,” Facchinelli says.

The reason for maintaining male mosquitoes in the population is because male mosquitoes do not bite, and therefore can’t spread disease. Female mosquitoes bite because they need blood to produce eggs, while males feed on nectar.

Research from Oxitec indicates this plan should work. In 2019, the company conducted trials with GMO mosquitoes in four Brazilian communities. They achieved mosquito population suppression rates ranging from 89% to 96%.

Many Residents and Environmental Groups Oppose the Decision

Florida Keys residents have collected over 230,000 signatures on Change.org petitioning the release of the mosquitoes, citing ecosystem disruption and public health and safety risks.

The Center for Food Safety (CFS), a nonprofit organization which has previously taken action against genetic engineering, released a statement denouncing the approval of the trial. The organization says Oxitec has not sufficiently addressed environmental and health risks. In the statement, CFS policy director Jaydee Hanson called the trial “a Jurassic Park experiment.”

CFS says there is a possibility of mutant mosquito offspring developing, based on a study of a previous Oxitec trial in Brazil. The trial, which utilized an earlier version of the GMO mosquitoes, resulted in "significant transfer" of the new mosquito genome into the natural population, instead of simply reducing the population size as planned. This may have unknown effects on disease control and transmission.

However, the specific genes that were artificially introduced into the Oxitec mosquito genome, known as transgenes, did not persist in the population over time. Facchinelli explains this is due to a “high fitness cost” which continuously limits the probability of genes being passed down.

Scientific evidence does not point to any adverse effects on human health from these GMO mosquitoes. 

Much of the public concern with this impending trial stems from the uncertainty of such a nascent field.

Laura Harrington, PhD, a professor of entomology at Cornell University, tells Verywell that there's a lack of trust between the public and the organizations responsible for introducing GMO mosquitoes.

“The level of transparency, especially early on, was not there,” she says.

While some environmentalists have raised concerns about ecological effects on food chains from this large addition of organisms, Harrington says this is not likely to be a major issue.

“It is only targeting one species of many in Florida that make up that biomass of food for other animals,” she says.

Genetically-Modified Mosquitoes Are Only Part of the Solution

Harrington says using GMO mosquitoes for mosquito population control is a major goal of many research labs. However, she cautions against the idea that this technology could be a silver bullet against disease carriers.

“Effective vector control will likely require multiple different strategies to reduce the risk of infection for people,” she says.

Facchinelli agrees. He sees these modified mosquitoes as a complementary tool that should be used in conjunction with more conventional mosquito control methods, like the chemical DDT and bacteria-based larvicides.

A timeline for the Florida trial has yet to be established, but the expectation is that the GMO mosquitoes will be released regularly over the course of multiple weeks.