Fighting Malaria with Genetically Modified Mosquitoes
By Fiorenzo Conte
One of the key components to control or eliminate vector-borne diseases is the control of the vector itself i.e. the mosquitoes. Two technologies have proven to be effective in controlling mosquitoes: insecticide treated nets and indoor residual spraying. Despite the facts that the achievement of a coverage significant enough to break the cycle of transmission has proven to be extremely challenging they are now part of the standard toolkit to fight malaria as endorsed by the WHO. Beyond the challenges associated with their distribution and utilization they present another shortfall: both of the solutions rely on the effectiveness of insecticide to kill the mosquito and as form of resistance become widespread their effectiveness is likely to decrease concomitantly. For this reason the scientific community has looked into a new strategy to control the vector: modify the genes of insects so that mosquitoes able to carry and transmit the parasite are suppressed. More precisely the technique now more in vogue is called sterile insect technique (SIT) which involves the release of sterile male insects at a high frequency that the probability of female mosquitoes to mate with non sterile male is greatly reduced and their offspring die. This technique is species sensitive (it is not susceptible to affect other species) and does not introduce new species of insect: for this reason it is considered by the scientific community to be disruptive only to a minimum extent.
However, GM mosquitoes can prove to be an emotive issue and the acceptance of the public opinion and of the media is a sine qua non to for the roll-out to be accepted. Public health campaigns like the polio vaccination in Nigeria proved that without an adequate information campaign public health campaign can backfire. And this has also been the case for experimental introduction of GM insects: the modification of genes in fact easily lends itself to a tampering-with-nature-technique label. During the 1970s the WHO was experimenting the introduction of sterile male mosquitoes to control malaria in India. This experiment was carried out at the same of a research commissioned by the WHO about biological weapons. The involvement of WHO in research about biological weapons (BW), mainly commissioned by the US, stirred suspicions that GM mosquitoes experiment could be related to BW and therefore traceable to the strategic and military interests of a western power. Suspicions were alimented by the fact that WHO was also introducing GM insects related to yellow fever (for the purpose of generic scientific research), even if the disease was not present in India. Although the WHO responded to these allegations, the credibility of the experiment was compromised to the point that the Indian government forced the WHO to stop the experiment. This case show how a lack of transparency and communication can breed conspiracy theories thus jeopardizing the neutrality of the research and with it the acceptability of the trial. The introduction of GM mosquitoes as any other public health interventions is far from being a merely technical or scientific questions and the possibility of its acceptability needs to be weighed also against the political and social background in which it takes place.
To avoid to run into such controversy a transparent regulatory process is needed: who is to regulate the GM mosquitoes and what coverage should the regulation have (national or regional) are some of the most sensitive questions. The regulation process is howver a very complex exercise given that it is fraught with bias typical of any research. The introduction of sterile mosquito might have consequences very different in its area of origin compared to an area where it has been recently introduced. Therefore, any assessment is case sensitive and its results are contingent upon the context in which the experiment took place. Another point is the choice of an appropriate counterfactual. There is a premise from which any regulation starts from: the introduction of GM will inevitably be associated with some degree of risk. However, to put it in the right perspective it is necessary to wage the possible harm of the new technology vis-à-vis the proper counterfactual. In the case of parasite carrying mosquitoes this is the death toll linked to vector born disease. In other words the question boils down to whether the potential risk of GM mosquitoes outweigh their potential of reducing the number of malaria and dengue fever deaths. Does the introduction of GM mosquitoes cause more harm than continuing to manage malaria and dengue in the conventional way? A farmer interviewed in Mali about the acceptability of GM mosquitoes seems to have a clear stand:
“If you can do it [engineer mosquitoes unable to carry malaria], it will be better, because malaria is more dangerous than any other consequences that this project could have“
HT to Wired Science