PUBLIC HEALTH
August 29, 2017

A GM Controversy in South Florida

The threat of dengue fever has inspired a move to genetically modify mosquitoes. But is the protection worth the risk?

There has been a plan in the works to release genetically modified mosquitoes in the Florida Keys since 2013. One scientist thinks that the release might finally come later this year. Yet if the past is any indication, release of the mosquitoes remains as uncertain as ever.

The Stealth Bomber of Mosquitoes

The wheels began spinning back in 2009, when cases of dengue fever, a tropical disease that can be deadly, were seen in Florida for the first time in 75 years. The culprit was the Aedes aegypti mosquito, which carries the dengue virus and can pass it on to people when it bites them.

Floridians really didn't need a new reason to go after these particular mosquitoes. Aedes have been called the stealth bombers of mosquitoes because they prefer to attack people from behind, dining on ankles and elbows, far away from any watchful eyes. They also prefer a buffet, biting many people in a day rather than drinking their fill at the first opportunity.

After first giving a preliminary approval, the FDA invited public comments on the trial. An analysis of these comments was recently published in JAMA.

With the re-appearance of dengue, these mosquitoes were no longer just a spectacular nuisance, they were also a public health threat, especially since they can also transmit the Zika virus to humans.

Florida officials settled on a plan to release genetically modified male mosquitoes that were tailored to pass on a lethal gene to their offspring. The new generation of mosquitoes, or at least most of them, would die before reaching adulthood. Oxitec, the British company engineering the modified males, had previously conducted releases of GM mosquitoes at three other locations outside of the United States. According to the company, a release in the Cayman Islands reduced the A. aegypti population by about 80 percent in three months.

Strong — and Mixed — Reactions to GM
As with most issues related to genetic modification, public reaction was mixed. The Florida Keys Mosquito Control District was in favor, while over 170,000 people showed their opposition to the plan by signing a petition against the release. In 2016, the FDA approved a plan to conduct the release in Key Haven, a tiny community in the Florida Keys.

After first giving a preliminary approval, the FDA invited public comments on the trial. An analysis of these comments was recently published in JAMA.

Over 2600 comments were submitted, and there were over three times as many comments opposing the trial as favoring it. The percentages were: 74.8 percent opposed; 21.6 percent in favor; and 3.6 percent neutral. Fears about the effects on human health, a general mistrust of genetic modification and concerns over the safety of the environment were the most common reasons given for opposing the release of GM mosquitoes.

As the authors point out, people who respond to FDA invitations for comments are rarely representative of the general public — for one thing, they're a lot more passionate. Yet the comments do echo the petition in showing that there is, at the very least, a vocal minority strongly opposed to releasing GM mosquitoes.

But not everyone in Florida is opposed to the release.

In November 2016, when most U.S. residents' thoughts were on the presidential election, Monroe County, Florida, residents were voting on a non-binding referendum on the mosquito release. Key Haven voted 65 percent to 35 percent against it. But it was one of only two precincts in Monroe County to do so. Monroe County as a whole voted 58 percent to 42 percent in favor of the release.

Confronted with this vote, Florida officials scrapped plans for the release in Key Haven but voted 3 to 2 to approve a new release at an as yet undetermined site in Monroe County. There will need to be a new approval from the FDA for the release to actually take place.

Trying A Different Strategy

With all the uncertainty surrounding the GM mosquito release, the Florida Keys conducted a different type of mosquito release from April to July of 2017.

Twice a week for 12 weeks, 20,000-40,000 male mosquitoes infected with the bacterium Wolbachia were released at various sites in Florida Keys. Because of the bacteria, when these mosquitoes mate with wild females, the eggs do not hatch. At least that's the plan. The bacteria also makes it more difficult for mosquitoes to harbor (and transmit) viruses like Zika. Should it work — and Florida is not the first place this approach has been tried — it would put a considerable dent in the mosquito population, possibly eliminating the need for any release of GM mosquitoes. Results are not in yet.

Perhaps the only certainty in this whole affair is that mosquitoes like Floridians a lot more than Floridians like their mosquitoes.

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