The Danger of Genetically Modified Mosquitoes
By Helen Wallace
The release of genetically modified (GM) insects should follow a precautionary approach, because what appears well understood in the lab can have unintended consequences when released on a large scale into the environment. On release, GM mosquitoes become part of a complex system involving predators and prey, other mosquito species, four types of dengue virus, other tropical diseases transmitted by mosquitoes, and the humans—including children—who are being bitten and infected.
An expert report (pdf) to the European Food Safety Authority lists a wide variety of issues that should be addressed prior to the deliberate release of any GM insects. They include the adverse effects associated with the flow of genes into the wild population; the interactions of the GM insect with target and nontarget organisms; the impact on agricultural management practices and on management measures to control insects that are vectors for diseases; and a variety of potential effects on human health. The latter include allergies and irritation; the presence of live female mosquitoes; potential changes in the ability of mosquitoes to transmit disease; and accidental ingestion (including of larvae and eggs). Other issues that have been raised elsewhere include: the potential for viruses to evolve into more virulent forms; the impacts on human immunity and hence cases of disease; whether other species of mosquito (transmitting the same or different diseases) might occupy the ecological niche vacated by a falling population of the target species (pdf); and whether infection with dengue has a protective effect against yellow fever.
The first open releases of GM mosquitoes have now taken place in the Cayman Islands, Malaysia and Brazil. In all three countries the biotechnology company Oxitec released GM Aedes aegypti mosquitoes (yellow fever mosquitoes) with the intention of reducing the population of this species, which also transmits dengue fever. In choosing the British Overseas Territory of the Cayman Islands to undertake the first releases, Oxitec bypassed the provisions of the Cartagena Protocol (covering impacts on biodiversity) and the Aarhus Convention (covering access to environmental information), both of which would apply in the U.K. The Cayman trials were in an inhabited area where dengue is not endemic; the smaller Malaysian trial was in an uninhabited area in a country where dengue is endemic; and the ongoing, much larger Brazilian trials are in an inhabited area where dengue is endemic. Only in Malaysia did the company openly consult the public, and even there, a small-scale release caused public concerns due to the lack of transparency about the timing and insufficient public information. Further, only a summary of the risk assessment has been published, leaving the regulator's decisions about what hazards to include, and whether or not they were significant, open to dispute.
Although no doubt genuine in its desire to tackle dengue fever, Oxitec is a commercial company with a patented technology to sell (pdf). Its business plan relies on convincing the governments of dengue endemic countries to pay for ongoing releases of its GM mosquitoes to maintain suppression of the mosquito population. Its investors include the University of Oxford, the venture capital company Oxford Capital Partners (which offers significant tax breaks to its investors), and a Boston-based multimillionaire (pdf). The former U.K. science minister, Lord Drayson, and the former president of the Royal Society, Lord May, have both acted as advisors to investors in the company. Oxitec has also received significant U.K. government subsidy via the Biotechnology and Biological Sciences Research Council as well as the Technology Strategy Board. Its open-release experiment in Malaysia was funded via a translational grant from the Wellcome Trust. Although the company is a spin-off from Oxford, the university's ethics board plays no role in overseeing its experiments.
Research on public attitudes to potential releases of GM mosquitoes to tackle malaria in Mali found that participants wanted to see evidence that GM mosquitoes could reduce malaria without adverse effects on human health and the environment, and many were skeptical that the technology would work. A majority of participants would support a release that satisfied their conditions, but a substantial minority would not support a release under any circumstances. Whereas it is difficult to extrapolate from a small study in a single country (which included mainly male participants), the study does succeed in raising some important issues. How is people's consent to be obtained for such experiments, given that most people would only grant it if certain conditions were fulfilled? And, is it ethical to undertake experiments if some people continue to oppose them?
Oxitec seems to have treated this ethical problem as largely an issue of public relations. In Cayman it released a video claiming its GM mosquitoes were sterile, rather than explaining that they breed and the offspring die as pupae; it also didn't mention that they were genetically modified. In Brazil activities have included attending carnival dressed up as mosquitoes. Concerns that the technology is not 100 percent effective, leaving some female (biting) mosquitoes to breed, have simply been ignored.
For observers, it is hard to understand how decades of debate at the World Health Organization and elsewhere have come to this. Is there really any regulatory oversight; any data required of any company; and any ethical requirements before GM insects can be released into the open? Decisions appear to be being taken by a small circle of powerful investors who have decided they must rush to commercialize a particular technology, rather than in consultation with the people who will be affected. Who is going to be liable if anything goes wrong? And will any problems be reversible as releases happen on an ever larger scale?
Helen Wallace is the director of GeneWatch UK. She has worked as an environmental scientist in academia and industry and as senior scientist at Greenpeace UK, where she was responsible for science and policy work on a range of issues. She has a degree in physics from the University of Bristol and a PhD in applied mathematics from University of Exeter
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