Genetically Modified Mosquitoes

Genetically modified mosquitoes may limit the spread of fatal diseases.


Genetically modified mosquitoes may not be able to smell carbon dioxide.


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The mosquito’s preferred meal is human blood and its eating regimen spreads deadly disease, such as malaria and dengue fever. Environmental control methods, which include spraying bug repellent and eliminating standing water where the pests breed, are difficult in the crowded, poor populations that suffer most from insect-borne illnesses—which is why molecular biologists are experimenting with ways to modify the bloodsuckers’ genetic code.

Discover (October 2011) reports that Anandasankar Ray, an entomologist at the University of California, Riverside, is genetically modifying mosquitoes by blocking their ability to smell carbon dioxide, which we humans exude with every breath. Biologist Anthony James, working in a lab just a few miles south at the University of California, Irvine, has hijacked a genetic region that controls flight in the Aedes aegypti mosquito. A. aegypti is the primary species that transmits dengue fever, explains Scientific American (November 2011), which infects 100 million people annually in tropical and subtropical regions and results in everything from mild flu symptoms to hemorrhaging and death. James zeroed in on crippling the flight muscles of the female mosquito while leaving males intact to repeatedly pass along their genetic code, thereby leading to a population crash.

James’ lab tests have proven effective, and the next tricky step is to move the experiments from a few mesh cages to the wild. He is following strict and slow protocol by setting up an approved release site in Chiapas, Mexico—unlike fellow scientist Luke Alphey, who in 2009 preemptively released genetically altered mosquitoes in the minimally regulated Cayman Islands, setting off a controversy among scientific and environmental groups.

Opponents believe it’s perilous for biologists “to breed large populations of a mosquito that they had explicitly programmed to die,” writes Scientific American. The magazine speculates on the possibility of a more aggressive species migrating to affected areas, filling the niche emptied by a few men playing God. Or perhaps the mass death of A. aegypti will disrupt regional food chains in unpredictable ways. “We need to respect nature as much as we can,” says Chiapas Undersecretary of Health Hermilo Domínguez Zárate. Still, given the potential to save the lives of millions, he concludes, “It’s worth the gamble.”