Touted by some to be a top medical breakthrough and others as an unnecessary risk, genetically engineered mosquito species have become a reality in efforts to control the spread of disease to humans.
Insects have transmitted diseases to humans throughout history. Mosquitoes typically spread disease more frequently in equatorial regions, but with global climate changes and increasing virulence of disease strain, geographic areas impacted are increasing. Several diseases, including Malaria and dengue fever, are commonly spread via mosquitoes.
There is no vaccine or approved medical treatment for dengue fever; therefore controlling the populations of mosquitoes is essential. Current population control measures are decidedly low-tech and include draining areas of standing water, the application of insecticides, and the use of insecticide-treated bed nets. These interventions have inherent challenges in access to and distribution of bed nets and insecticides, human exposures to hazardous chemicals, environmental degradation, and creating insecticide-resistant mosquitoes.
Taking the “bite” out of the bug
A field test of genetically modified male mosquitoes was conducted on Grand Cayman Island at the end of 2009 and the report was recently published by Nature Biotechnology. The modified mosquitoes were developed by Oxitec, a British biotechnology company, to reduce the spread of the dengue virus. They used a variation of the Sterile Insect Technique (SIT) that has been used successfully to control several agricultural pest insects. Rather than sterilize the mosquitoes using radiation which damages the viability of the mosquito, Oxitec modified the genetic make-up of the laboratory mosquitoes to include a dominant lethal gene in which offspring would not survive to adulthood. Based on this field test it was concluded that genetically modified mosquitoes are able to compete with wild male mosquitoes for mates outside of a laboratory controlled environment. This suggests that it is possible to reduce the number of mosquitoes that may carry the dengue virus through the regular release of genetically engineered male mosquitoes.
So, what does this mean?
- Mosquito species are not being removed from the environment and would continue to be a part of local food webs and ecological niches.
- The genetically modified mosquitoes are not self-sustaining due to the lethal gene that has been integrated. To sustain results of reduced mosquito populations, regular releases would need to occur.
- The mosquitoes being genetically altered belong to a specific species of mosquito, Aedes aegypti, which is responsible for the spread of the dengue virus.
While uncertainties exist over the potential for unforeseen consequences and public backlash, like what has been seen in the use of genetically modified crops and agriculture, what is certain is that this is likely only the first in many field tests to come. In fact, if you live in the Florida Keys, where the first cases of dengue fever were reported in 2009, genetically modified mosquitoes may be coming to a neighborhood near you as early as this spring.
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Harris, A.F, Nimmo, D., McKemey, A. R., Kelly, N., Scaife, S., Donnelly, C. A., Beech, C., Petrie, W.D., & Alphey, L. (November 2011). Field performance of engineered male mosquitoes. Nature Biotechnology (29, 11). P. 1034-1037. online
Ostera, G. R. & Gostin, L. O. (March 2011). Biosafety concerns involving genetically modified mosquitoes to combat malaria and dengue in developing countries. Journal of the American Medical Association (305,9). P 930-931. online
Shelly, T. & McInnis, D. (November 2011). Road test for genetically modified mosquitoes. Nature Biotechnology (29, 11). P. 984-985. online