Dengue fever and chikungunya are transmitted to humans by two species of mosquitos, Aedes aegypti and Aedes albopictus. There are no vaccines for these viral diseases and while not often fatal, they can disable victims with painful symptoms for weeks or months. Infections are common across the tropics, and increasingly being found in the southern United States.
Reducing numbers of Aedes mosquitoes is vital to protecting human health. But because Aedes breed in very small pools of water (even a cup is suitable) and adults are active during the day, traditional pesticides are of limited use. The release of genetically modified Aedes mosquitoes, whose offspring die before reaching maturity, provides real hope for reducing mosquito numbers without insecticides.
Small-scale experimental releases of GM mosquitos in Grand Cayman and Malaysia showed little impact on local ecosystems. Most of the 6,000 males released in Malaysia survived fewer than 3 days and flew less than 200 feet from where they were released. Successful population control will require repeated releases of large numbers of GM mosquitoes, and less is known about ecological effects at this scale.
The flux in environmental conditions — which have important influences on species composition, survivorship, and the size of adults, ultimately determining how effective a mosquito is at transmitting disease — makes it difficult to predict how a large-scale release of GM mosquitoes will impact the abundance and transmission potential of Aedes or other mosquito species.
What we do know is that nearly half the world's population is already at risk for mosquito-borne disease. Field release trials of GM mosquitoes will assess the potential for this technique to address this major global health threat. Potential risks are likely to be less damaging than the known impacts of pesticide use on amphibians and birds. And when mosquitoes cause serious human suffering, the risks of pesticides have been consistently deemed acceptable.