For The First Time, Genetically Engineered Mosquitoes Are Released Into The Wild

The transgenic animals are designed to help stamp out dengue fever in the Cayman Islands
Germán Meyer

An Oxford-based research firm has announced the results of a release of genetically modified male mosquitoes in the Cayman Islands, the first experiment with GM mosquitoes to take place in the wild.

From May to October of this year, Oxitec released male mosquitoes three times a week in a 40-acre area. The mosquitoes had been genetically modified to be sterile, so that when they mated with the indigenous female mosquitoes there would be no offspring, and the population would shrink.

Mosquito numbers in the region had dropped 80 percent by August, which the researchers expect would result in fewer dengue cases.

Since it’s only females who bite humans and transmit diseases like the untreatable dengue fever this study examined, British biologists suspected that introducing males sterilized by a genetic mutation into the gene pool could dramatically decrease their numbers over time.

While many scientists and environmentalists object to killing off mosquitoes entirely for fear it would harm dependent species, Oxitec asserts that, since the sterilizing gene could not be passed on to subsequent generations, this method will have no permanent ecological impact.

Rather, GM males function like an insecticide, temporarily reducing numbers without the negative effects of using chemical toxins. They can also be more effective against insects that had developed resistance to certain commonly-used pesticides. In regions where booming mosquito populations are have caused epidemic outbreaks of dengue fever, yellow fever and malaria, dramatically reducing the population temporarily could reduce the death toll, and provide valuable lead time to vaccinate and treat hard-hit populations.

As the death toll caused by disease-carrying mosquitoes rises (over 2 million of the 700 million people infected by mosquitoes die annually), science has proposed a wide range of possible solutions to lessen the damage, from lasers to chemicals. But the release of transgenic animals into the wild is a very bold new step.