Let's kill all the mosquitoes

Knipling won the World Food Prize for his work and was named to the Cattlemen’s Association Hall of Fame. His “sterile insect technique” appealed not just to ranchers but to environmentalists. In 1962, Rachel Carson published Silent Spring, her epochal broadside against the chemical industry. In the final chapter of that book, called “The Other Road,” Carson singles out some “new, imaginative, and creative approaches to the problem of sharing our earth with other creatures.” Chief among those was Knipling’s method—“a triumphant demonstration of the worth of scientific creativity,” she wrote, “aided by thorough basic research, persistence, and determination.”

So why haven’t scientists tried to use the same approach in the fight against mosquitoes? Actually, they have. The problem was that mosquitoes proved too fragile for the X-rays: Instead of turning sterile, the bugs just died. But in recent years, the sterile insect technique has been revived. One researcher, Luke Alphey, used genetic engineering to design a sterile strain of Aedes aegypti mosquito—the kind that carries Zika, dengue, and yellow fever. Alphey’s technique is very clever: The bugs hold a gene that kills them at the larval stage, unless they’re reared in the presence of tetracycline, a common antibiotic. That means it’s possible to breed large numbers of the flies in the lab, but when they’re released into the world, they cannot reproduce.

In 2002, Alphey founded Oxitec, which would become the first company to deploy genetically modified mosquitoes as a weapon. Since 2010, the firm has performed field evaluations in Brazil, the Cayman Islands, and Panama. The treatment works like this: Oxitec employees drive a van around mosquito-ridden areas at five or 10 miles per hour. A bladeless fan propels genetically modified males out through a plastic tube, and then the bugs seek and interbreed with wild females. (At a test site in Brazil, Oxitec released 800,000 flies per week, for half a year.) According to the company’s head of field operations, Andy McKemey, each of these field evaluations has resulted in at least a 90 percent decrease in the local population.