By Lim Li Ching

In December 2010, 6,000 genetically modified mosquitoes were released in my country, Malaysia. This followed releases of large numbers of mosquitoes engineered with the same modification—a dominant lethal gene—in the Cayman Islands, where over 3.3 million GM mosquitoes were released in 2009 and 2010. Since February 2011, more than 3 million of these mosquitoes were released in the city of Juaziero in northeastern Brazil. The release of these same mosquitoes is currently being considered in the Florida Keys in the United States. Many other countries are reportedly evaluating the GM mosquitoes for laboratory research and possible future field releases.

The genetic modification in question targets Aedes aegypti, commonly known as the yellow fever mosquito, which is a vector of dengue fever and other diseases. The so-called RIDL technology involves a genetic regulation that, in the absence of the antibiotic tetracycline, causes death at the larval stage of the offspring. The release of mainly male GM mosquitoes carrying this lethal gene is intended to result in mosquito population suppression, with the consequent aim of reducing the incidence of dengue fever.

The GM mosquitoes were developed and the associated technology patented by the UK-based company Oxitec, which appears to be approaching many countries and offering the mosquitoes as a potential solution to the dengue problem. Dengue fever is a serious problem in many countries, and authorities are increasingly looking for alternatives, as tools such as pesticides are rendered ineffective due to resistance development.

However, the release of these GM mosquitoes into the environment raises many scientific, social, ethical and regulatory concerns. Even while these issues are still being debated, it seems that there is a headlong rush to release the GM mosquitoes.

The situation is compounded by the fact that the international regulatory and risk assessment frameworks governing GM insects in general, and GM mosquitoes in particular, are still immature. So much so that in the US, discussion is on-going as to which agency should regulate the proposed release of GM mosquitoes in Florida, since this is a completely new area which the regulatory world is unfamiliar with.

Moreover, under the Cartagena Protocol on Biosafety—the only international law dealing exclusively with genetic engineering and genetically modified organisms—a technical expert group revised its guidance last year for GM mosquito risk assessment. This guidance, part of a larger package of guidance on risk assessment, will be forwarded to the Parties of the Cartagena Protocol for consideration in October 2012. To my knowledge, a corresponding group which convened under the World Health Organization to develop guidance principles for GM mosquito evaluation has yet to finish this task.

At the national level, the first release of GM mosquitoes in the world, which occurred in the Cayman Islands, was conducted in the absence of a biosafety law. While the release was approved by the authorities concerned, the Cayman Islands only had a draft biosafety bill at the time. Moreover, the provisions of the Cartagena Protocol did not apply to the Cayman Islands, even though the UK, under which the Caymans are a British Overseas Territory, is a Party to the Protocol. This meant that specific biosafety questions may not have been fully considered nor evaluated, because of the absence of a detailed and comprehensive biosafety regulatory framework.

Indeed, the risk assessment that was used to support the approval of the releases in the Cayman Islands has been roundly criticized. Scientists at the Max Planck Institute for Evolutionary Biology in Germany  conducted a thorough examination of the regulatory procedures and documents. They concluded that the risk assessment was incomplete, with no provision of experimental data on the releases; that there was poor referencing (unlikely to meet peer review standards); and worst of all, that there was a marked absence of discussion of the potential health or environmental hazards specific to the GM mosquito in question.

This trend of substandard regulatory oversight is regrettably not a one-off. The Max Planck scientists assessed the regulatory process in the first three countries (US, Cayman Islands, Malaysia) permitting releases of GM insects (including GM mosquitoes in the latter two countries) in terms of pre-release transparency and scientific quality, and found the process wanting. They suggest deficits in the scientific quality of the regulatory documents and a general absence of accurate experimental descriptions available to the public prior to the releases.

Worryingly, they judged the world's first environmental impact statement on GM insects, produced by US authorities in 2008, to be scientifically deficient. This assertion is made on the basis that (1) by and large, the consideration of environmental risk was too generic to be scientifically meaningful; (2) it relied on unpublished data to establish central scientific points; and (3) despite the approximately 170 scientific publications cited, the endorsement of the majority of novel transgenic approaches was based on just two laboratory studies of only one of the four species covered by the document. However, the environmental impact statement appears to be used as the basis for regulatory approvals around the world, including that of the GM mosquitoes.

One of the most obvious questions to ask is whether humans can be bitten by the GM mosquitoes. In public information available on the Cayman Islands and Malaysian trials, however, this question is either conspicuously ignored or it is implied that there is no biting risk, 'as only male mosquitoes are released and they cannot bite.'

However, as detailed by the Max Planck scientists, it is probable that transgenic daughters of the released males will bite humans. This is because the males are only partially sterile as the technology is not 100 percent effective. Furthermore, if the mosquitoes encounter tetracycline contamination in the wild, the numbers of survivors could increase. The likely presence of transgenic females in the environment requires the consideration of a more complex series of potential hazards, but this does not appear to have been done.

Public information, consultation and participation have been also lacking. In the case of the Cayman Islands, while Oxitec and the local Mosquito Research and Control Unit claim that adequate information was provided to the public prior to the release of the GM mosquitoes, the video information provided by MRCU for outreach does not once mention that the mosquitoes in question are genetically modified. Moreover, given the significance of the first release of GM mosquitoes in the world, it is puzzling as to why Oxitec only announced the fact of the release more than a year after they occurred, catching even scientists in the field of transgenic insects off guard.

It is clear that the regulatory processes that have governed the release of GM mosquitoes into the environment so far have been lacking. While international guidance may have recently been completed, the implementation at national level still suffers from a lack of adequate experience in dealing with this novel application of genetic engineering, a lack of rigorous risk assessment and robust investigation of unanswered questions and a lack of effective and meaningful public consultation and participation. In light of this, the push to release the GM mosquitoes in various countries is grossly premature.


Lim Li Ching, M.Phil., works in the biosafety program at Third World Network and is Deputy Editor of Science in Society.

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