Malaria Resistant Mosquitoes
Genetically Modified Mosquitoes Could Help Reduce Malaria Cases
The creation of malaria resistant mosquitoes using genetic modification has potential, but there are still problems to be solved before this technology can be used.
“Mosquitoes are the most important insect vectors of human disease and the most common bloodsucking arthropods” (Schmidt and Roberts, 2000, p. 572). No wonder scientists are busily trying to develop malaria resistant mosquitoes, dengue resistant mosquitoes, mosquitoes with shorter life spans, and mosquito eradication schemes.
In March 2007, we heard of a breakthrough: scientists have created a genetically modified mosquito that is resistant to malaria and more robust than its malaria-infected indigenous counterparts. This achievement could be important because malaria kills more than a million people every year (Schmidt and Roberts, 2000, p. 572) - the genetically modified mosquitoes could eventually replace the indigenous insects and bring down the incidence of human malaria cases dramatically.
The malaria resistant mosquitoes, developed by Marrelli, Li, Rasgon, and Jacobs-Lorena, won’t be flying free and saving lives any time soon however. There are still a number of hurdles to jump before that can happen:
- The genetically modified mosquitoes are Anopheles stephensi, the species of malaria parasite that they are resistant to is Plasmodium berghei, and the mosquitoes were fed on mice. What humans chiefly need is an Anopheles gambiae mosquitoe that is resistant to Plasmodium falciparum acquired by feeding on a human. Though the genetic modification works in the alternate scenario, there is no guarantee (yet) that it will work in the desired one.
- The plan would presumably involve releasing large numbers of robust malaria resistant mosquitoes into the environment and then waiting while they outmanoeuvred the native mosquitoes and eventually replaced them. Considering the misery that mosquitoes can inflict – even when they are not carrying disease – the people living in the area would have to be utterly certain the scheme would work before they would agree to it. The threat would be lessened if only males were released (males do not bite), but even then, in order for the process to work the males would have to reproduce.
- The malaria resistant mosquitoes are genetically modified. Opponents will argue that we don’t know enough about unintended and unanticipated consequences of releasing genetically modified organisms into the wild. What other diseases might they be capable of transmitting? What sort of pest might they become as they evolve in the future? Could there be any unanticipated effects on the species that they bite, or on the species that feed on them? It will be very difficult for scientists to answer these questions with absolute confidence - and history is full of examples of manipulations of nature with unfortunate unintended consequences.
- The use of this technology to combat malaria will involve scientists from developed Western countries working in economically disadvantaged and vulnerable regions of the world. Understandably, the people in these regions do not wish to be the guinea pigs for rich-world experiments. Any plan to release genetically modified bloodsucking disease vectors would have to include meaningful local involvement with excellent culturally sensitive communication and education, starting well ahead of time.
Other interesting content about mosquitoes:
Mosquito Borne Disease Prevention
Sources:
M. Marrelli et al., "Transgenic malaria-resistant mosquitoes have a fitness advantage when feeding on Plasmodium-infected blood," PNAS, March 27, 2007.
Schmidt, Gerald D. and Larry S. Roberts. Foundations of Parasitology 6th Ed. Boston: McGraw Hill, 2000.
