LAGOS, Nigeria – It’s no wonder that Goethe wrote “The Sorcerer’s Apprentice” near the dawn of the industrial age. The poem, which most of us now learn from Mickey Mouse, tells the story of a young man who, left to his own devices, mimics his boss’s spell for making brooms fetch water pails.
Once the task is done, he doesn’t know how to stop the thing, so he chops the broom in half, which only enables it to work double duty. The sorcerer eventually returns, fixing the mess his subordinate has made (his situation never got quite as out of hand as Mickey’s). Lesson learned: Solutions to problems at hand can create new, sometimes unforeseeable, challenges in the future.
As scientists consider using genetically modified mosquitoes to combat deadly diseases in the developing world, Goethe’s poem should serve as a warning. Scientists are aware that their interventions in the natural world will have unintended effects, and in order to behave ethically, these potential risks must be considered. Even something as innocuous as a mosquito net may carry a considerable downside.
A mosquito net is a simple piece of technology: it creates a protective barrier between sleeping humans and the disease-carrying mosquitoes that would otherwise feast on them during the night. Combined with antimalarial drugs and in-home spraying of pesticide, nets are responsible for a 25 percent drop in global malaria deaths since 2000. But in Kenya, Tanzania and other countries that use bed nets, scientists are beginning to see evidence of a new problem: mosquitoes might be adapting to the solution, finding workarounds.
We are the mosquitoes’ food, Nora Haenn, an anthropologist at North Carolina State University, reminded me, and like most creatures, they feed where the food is. (Or in this case, when it is.) Mosquito nets work because the mosquitoes most responsible for transmitting malaria in sub-Saharan Africa feed at night. But now they’re trying their luck earlier, and outdoors. In other cases, night-feeding species seem to be losing ground to more flexible competitors — these also carry malaria.
Researchers have yet to prove definitively that mosquitoes are adapting their behavior in response to nets, but Haenn brought up the possibility to make a point: By solving certain problems, we often create new ones. For Haenn, who is part of an interdisciplinary program at N.C. State aimed at inserting discussions about ethics and responsibility into the early stages of biotech research, the side effects of scientific meddling weigh heavily.
There are many different organizations experimenting with mosquitoes in an effort to eradicate malaria and dengue fever — Haenn’s colleagues at N.C. State; a group at the University of California, Irvine; and Oxitec, a private company in England. Of the many ways to tinker with mosquito DNA, two strategies are promising.
One approach, focused on dengue, aims to reduce the mosquito population by making it difficult for them to breed. Fred Gould, an entomologist at N.C. State, has been involved in an effort to design mosquitoes that produce flightless females. Only female mosquitoes draw blood, which they must do in order to reproduce. If they can’t get off the ground, it will become impossible for them to mate, and the subsequent generation will be smaller than it would have been otherwise.
The other approach, focused on malaria, won’t get rid of the pesky things, but it will make them less deadly. There are different types of malaria, Anthony A. James, a professor of microbiology at the University of California, Irvine, told me, and they’re host-specific. Mice can’t catch human malaria, and vice versa. James takes the genes that help mice fend off human malaria and transfers them into mosquitoes.
Theoretically these altered mosquitoes would destroy the disease in their own bodies instead of spreading it to humans. To make it work on a large scale, scientists would have to connect this gene to what James calls “a drive system” — some trait that makes the malaria-immune mosquitoes more likely to reproduce than their normal cousins. Should someone figure out how to do this with mosquito DNA, natural selection would do the rest.
It’s a clever solution. But all solutions, whether as simple as a net or as complicated as splicing genes, come with risks. For instance, Aedes aegypti is the species primarily responsible for spreading dengue. It’s present around the world, but outside North Africa, it’s an invasive species.
If scientists use flightless female modifications against A. aegypti and succeed in decreasing its presence in, say, Mexico City, then what will fill its ecological niche there? (What is its ecological niche anyway? One entomologist told me that we don’t even have a great understanding of mosquitoes’ place in our ecosystem, because we have focused our efforts on killing them rather than observing them.)
Even curing a disease poses risks, because in all likelihood it won’t stay cured forever. If G.M. mosquitoes completely neutered the malaria parasite’s threat, even in one part of the world, it would be an incredible success story. But what happens if the parasite adapts to circumvent the tools we’ve used to fight it?
Today we know how to take precautions to prevent malaria transmissions and fight the disease with antimalarial drugs. But in the future, some version of malaria could surge through a population of humans without the cultural knowledge or pharmaceuticals necessary to defend themselves against it.
This sort of risk-taking is a hallmark of contemporary civilization. In 1986, the German sociologist Ulrich Beck coined the term “risk society” as a way of describing the shift in science and technology’s relationship to risk over the past century. For most of human history, Beck argues, risks came from unknowable and uncontrollable forces — natural disasters, famine, disease.
So we focused on mitigating those external risks. Today we have at least partial solutions to many natural risks — levees, industrial farming and antibiotics, say — but each solution contributes to new risks — more destructive floods, obesity and drug-resistant diseases — which then have to be managed with new solutions, which then present new risks.
