Mosquito District workshop focuses on Keys trials


Oxitec’s second-generation technology is delivered in boxes to be placed around neighborhoods. The trial has been approved by federal and state governments and the Florida Keys Mosquito Control District will vote soon to approve or deny the test in the Florida Keys. CONTRIBUTED

Now that the Oxitec “Friendly Mosquito” trials have been approved by the federal and state governments, it’s up to the Florida Keys Mosquito Control District to decide if, when and where to embrace the technology said to decrease the chances of mosquito-borne diseases such as dengue fever (there are two new cases in the Keys; see sidebar) and zika. 

On June 23, the FKMCD held a virtual meeting with key personnel from Oxitec, as well as Monroe County Health Officer Bob Eadie, to bring the Keys up to speed on the company’s second-generation technology it proposes to try in the Keys.

Eadie endorsed the proposed trials in Monroe County. 

“You can never have enough tools,” he said, referring to the Oxitec technology. “As we go forward we need to figure out how to control any type of outbreaks of infectious diseases. I go back to COVID. It’s possible we can create a vaccine for that, but decades of trials for a dengue vaccine have not been successful. We need some way to protect the public from mosquito borne diseases and this looks like viable technology.”

Oxitec has been working closely with the FKMCD for about a decade, anticipating the recent decision to allow experimental trials to go forward. 

In both versions of the technology, Oxitec takes a biologically modified mosquito and uses tetracycline to keep it alive to adulthood so that it can mate. A very basic layman’s explanation of the procedure is to say that when the tetracycline applications stop (when the mosquitoes are released into the wild), the mosquitoes and offspring die. In the 2nd generation technology, only female breeders are treated with tetracycline in the lab in the U.K. Then the male-only eggs can be shipped globally for distribution. Boxes of the male-only eggs can be placed in neighborhoods. Once in place, water and fluorescent markers are added to the boxes. 

On Tuesday, Oxitec laid out a plan for the FKMCD’s consideration. In the first phase, lasting 12 weeks, Oxitec would place boxes in a specific area and then collect data and evaluate the results. In the second phase, lasting 16 weeks, the trial would expand to a wider area and, again, the release rates would be evaluated. The whole project, Oxitec officials said, would last about 28 weeks and involve about 130 boxes of the second generation technology. Should the FKMCD vote to begin the trials, all of the costs would be borne by Oxitec.

The board also discussed whether or not to conduct another non-binding referendum and possible locales for the trial.

Four FKMCD board members spoke out in opposition of another referendum; Dr. Stan Zuba did not offer an opinion. 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.

FKMCD attorney Dirk Smits said the board could have another referendum but it would be non-binding. “The only thing you can do is another straw vote,” he said. “You can’t do a binding giveaway of your power. It’s just not possible.”

As to where the trials might be conducted, the focus has shifted north to the Middle and Upper Keys. According to FKMCD’s Catherin Prusynski, trap data shows a daily average of 5.3 Aedes aegypti mosquitoes per trap in the Lower Keys, 14.1 in the Middle Keys and 23.9 in the Upper Keys. 

“We are still analyzing the data,” Prusynski said. “We think that the Aedes aegypti mosquito is still about 4% of the mosquito population in the Keys, but we have a large population blowing in from the Everglades. We’ve been concentrating our efforts in the Lower Keys because that’s where the dengue outbreak was in 2009-2010. Now we are focusing our attention on Key Largo as well as Marathon.”

The FKMCD board will hold another workshop, solely for the purpose of public comment on the Oxitec trial. The date has not been determined as of presstime.

After Oxitec’s virtual presentation, the FKMCD board has a chance to ask questions. The chat box of the Go To Meeting platform was active during the presentation, and some board members asked questions posed by the public.


FKMCD board member Tom McDonald: Some have expressed concern about this trial, as being an experiment on human begins. This technology has been used near millions of people in Brazil and the Cayman Islands. Wouldn’t there be evidence it would cause problems for humans?

Oxitec: We are releasing male mosquitoes only that don’t bite humans, they feed on nectar. We have released billions of first-generation mosquitoes in Brazil with no adverse effects. That has been validated by the Brazillian authorities.

FKMCD board member Stan Zuba cited articles in the Boston Globe and a paper from a symposium conducted at University of Illinois,  Urbana-Champaign campus. One talked about the risk benefit analysis and the other mentioned the number of comments opposing the release of GMO mosquitoes on the EPA public comment for the experimental trial permit. 

Oxitec: As far as the risk benefit analysis, while we aren’t in danger from a mosquito-borne illness in the U.S. right now, we don’t know when the next outbreak is coming. But it will come. It’s important to prepare these tools in advance. The EPA logged 31,000 public comments against the trial, but the agency found that about 30,000 were form letters — copy and paste. 

FKMCD board member Brandon Pinder: If an Oxitec mosquito mated with a wild mosquito carrying a tropical disease, could that be passed to the offspring allowing for mutation of the virus? Is it possible for Oxitec mosquitoes to persist in the wild and become “super mosquitoes”?

Oxitec: A lot, if not all, of the female offspring of that mating are going to die, and it’s the female that could transmit. Even if there were mutations, it couldn’t be transmitted for very long. There is no evidence that something like that could happen and there is no mechanism for it to happen. The super mosquito reference is from a 2019 paper that has since been discredited by the editors of that publication. In fact, the paper’s data showed the opposite. The EPA looked at that as well and reached the same conclusion as the publication editors.

FKMCD chairman Phil Goodman: What results can we look for to determine whether or not the trial was a success?

Oxitec: We are expecting to measure a whole range of items and then compare the difference between treated and untreated areas will be the key criteria. We will be monitoring how many of the wild female mosquitoes die. That will determine the effectiveness, how many wild female mosquitoes were covered by our males.

FKMCD McDonald: Can we make a determination about the cost savings of using Oxitec? Are there any models?

Oxitec: We have not yet modeled cost effects for the Keys specifically. Oxitec is pursuing this technology in hopes it has an impact. No one on our team is concerned about generating massive profits over public safety. COVID is showing us what public and private partnerships can do when a public health challenge presents itself. 

According to Oxitec, this is how the second-generation technology works:  “A self-limiting gene allows us to release maleonly cohorts of adult mosquitoes into the environment, which mate with pest females, and the self-limiting gene prevents female offspring from surviving. With sustained releases of self-limiting males the number of pest females in the population declines, and the target pest population declines. Our insects also carry a fluorescent marker gene which allows for easy and effective monitoring of performance. The self-limiting gene is only active in females, therefore preventing females from surviving; males are not affected by this gene, so can survive as normal. It is designed to prevent survival of female offspring to allow for production of male-only cohorts of mosquitoes. In the field, it is female Aedes aegypti that bite humans and transmit diseases such as dengue and Zika viruses.

Sara Matthis
Sara Matthis thinks community journalism is important, but not serious; likes weird and wonderful children (she has two); and occasionally tortures herself with sprint-distance triathlons, but only if she has a good chance of beating her sister.