An environmental group is questioning the Florida Keys Mosquito Control District's plan to introduce sterile mosquitoes into the Keys to battle the spread of dengue fever.
The district has partnered with the England-based company Oxitec on the project and plans to introduce the mosquitoes sometime in 2012. The district is currently waiting on federal and state approval to test the technology, Executive Director Michael Doyle said.
The Keys would be the first community in the United States to test the technology.
The agency is targeting the Aedes aegypti mosquito because it is the species that is known to transmit dengue fever, a virus that hit Key West in 2009 and stayed around through 2010. There were no documented cases in 2011, according to the Monroe County Health Department.
The genetically engineered mosquitoes would be bred in a lab until adulthood, after which the males would be released into the wild. In theory, the males, which don't bite, would mate and then die off. The offspring would die early in life -- in the late larvae or pupae stage -- and the mosquito population in a given area would theoretically be suppressed.
The district and Oxitec intend to release 5,000 to 10,000 genetically engineered mosquitoes during a two-week period and release them into an undisclosed 36-square-acre block near the Key West Cemetery, where the first case of dengue was reported. The initial trial is expected to last about two months. The mosquitoes will be dusted with a fluorescent powder for identification purposes and then trapped to see how far they are flying
Questioning its success
The environmental group Friends of the Earth released a report this month that questions Oxitec's technology success and whether the district should move forward with the tests. The group raises concerns about the cost and the long-term impacts on the environment. The group also questions what state and federal agencies should be overseeing these test trials.
"While attempts to limit the spread of disease are laudable, there are many regulatory, environmental and ethical challenges facing the release of GE (genetically engineered) mosquitoes in the United States and there are even more unanswered questions," the group wrote in its position paper. "The behavior of these mosquitoes and the risks they pose to human health and the environment are hard to predict, leaving the public with more questions than answers."
Friends of the Earth argued that the science can only reduce mosquito populations in the immediate term in controlled settings.
Oxitec has not proven that such population reductions lead to disease eradication, said Eric Hoffman, a biotechnology campaigner with Friends of the Earth.
The group calls Oxitec's claims misleading. The mosquitoes are not in fact sterile, but are engineered to pass on an "autocidal" gene that kills their offspring, the report states.
Oxitec's technology does not make its mosquitoes sterile; rather, they are engineered to be dependent on tetracycline and die in its absence.
"Unfortunately, its system has many problems that raise serious questions about the viability of GE insects as a way to limit the spread of disease," the group wrote. "Oxitec has not proven such population reductions lead to disease eradication."
Friends of Earth also questions how cost-effective the program will be in the long-term. Doyle said the program could cost between $200,000 and $400,000 a year and would require a full-time and part-time position to be assigned to the program.
The system locks communities and nations into a permanent scheme of repeated, ongoing payments to Oxitec once releases begin, since Oxitec's mosquitoes are patented, according to Friends of Earth.
"The company stands to make significant profits if countries and communities must make continuous payments to it," the group's report states. "These payments would presumably continue endlessly unless the community wanted the release of genetically engineered mosquitoes to stop, in which case disease prevalence could rise when conventional mosquito populations rebound. The company has yet to provide data on what would happen to mosquito populations or prevalence of disease if releases were halted."
Oxitec Chief Executive Officer Hadyn Parry contends that field trials in the Cayman Islands in 2009 and 2010 were successful, with the technology wiping out 80 percent of the Aedes aegypti in one test area.
Upsetting the balance
Friends of the Earth raises the question that a significant decline in the Aedes aegypti mosquito population could have unintended consequences on the local ecosystem and food chain. Mosquitoes are an important source of food for many fish, birds and other insects that would need to find another food source if Aedes aegypti was to disappear, Hoffman said. The impact their decline would have on the food chains in Florida have yet to be studied.
Their decline could also leave an ecological niche to be filled by other, possibly more harmful pests, according to the Friends of the Earth. For example, the Asian tiger mosquito, Aedes albopictus, is considered one of the most invasive species in the world and carries many diseases, including dengue fever and the West Nile virus. While the Asian tiger mosquito has not yet been found in the Keys, it could spread to the islands if other mosquito populations decline, as it has spread across many parts of the United States, the group stated in its report.
This could mean the spread of more disease and increased use of pesticides. The impacts from other, potentially more dangerous insects taking over the ecological niche left by Aedes aegypti have yet to be studied, the group states.
The dengue virus could evolve and become more virulent in response to the introduction of genetically engineered mosquitoes, the report states.
"The fact is that the virulence and spread of disease combined with mosquito population levels and behavior involve incredibly complex systems and difficult to predict in advance," the report states. "Significantly more research is needed on these and other potentially unintended consequences of the introduction GE mosquitoes."
One local environmentalist is also concerned about the impact it will have on Keys ecosystems.
"We really don't know what the outcome will be," said Michael Welber, who has worked with several local environmental groups. "Is the limited success worth the risks? This is the great unknown. Should we be screwing around with the balance of nature?"
Doyle called the group's comment about the potential influx of the Asian tiger mosquito a "valid concern," and remarked that they are "more aggressive."
However, Doyle doubted a breakdown in the food chain or other environmental meltdown, as the Aedis aegypti tends to hide in dark places such as tin cans and other small enclosed places away from predators, he said.
"Many of these will require an in-depth evaluation and response. They aren't easy answers for any of us to communicate effectively," Doyle said. "Most will likely be addressed over the next several months during the permitting process. Do keep in mind that none of this will happen unless the agencies approve it. ... Regardless, we have plenty of time to look at these issues in depth, and if everyone is convinced it's worth doing, we'll open it up for public discussion long before starting any field experiments."
The Aedes aegypti is a non-native species that came from Africa, so its removal would have little impact on the health of the ecosystem, Parry said, calling it a "recent entrant."
The federal government is still trying to work out which government agency would permit the test, Doyle said. The state Department of Agriculture and Consumer Services has "entertained" the idea of permitting the test on the state side, Doyle said.
The technology is an alternative to using pesticides. Also, this allows the district to target a specific species and not kill other species through the use of pesticides, Doyle said.
"It is promising enough to try it," Doyle said.