Even before the Zika virus, mosquitoes were the deadliest creatures on the planet. But gene modification means these blood suckers’ days might be numbered. Is it dangerous to talk about ‘editing nature’, or should we consider eradicating them for good?
When an Aedes aegypti mosquito bites you, she – because only the females, which need blood as nutrients for their offspring, bite – will probe your skin with her proboscis as many as 20 times. Two pairs of sharp cutting edges, the fascicle, break the skin and then search for a blood vessel, withdrawing and re-entering until a suitable target is found. When the blood starts to flow, a salivary tube delivers a protein that stops it clotting. The mosquito holds still and then begins to suck; in 90 seconds’ time, she feels full, and stops. And then, if you are in parts of South and Central America and bang out of luck, you will have Zika.
It’s a horrible idea, and one that will draw shudders from anyone who has ever been bitten by a mosquito – which is to say, just about everyone. In the entire animal kingdom, the mosquito occupies a special place as receptacle for our hatred and disgust. Even the great and generous EO Wilson, author of the touchstone argument for preserving biodiversity, The Creation: An Appeal to Save Life on Earth, makes an exception for anopheles gambiae, which spreads malaria in Africa. “Keep their DNA for future research,” he writes, “and let them go.”
When Wilson thus hardens his heart, he speaks for us all. Where we revere and anthropomorphise such brutal predators as sharks, tigers and bears, we view these tiny ectoparasites as worthless, an evolutionary accident with no redeeming or adorable characteristics. No one ever had a cuddly mosquito. Thanks to malaria, they have probably helped to kill more than half of all humans ever to have lived. Today, according to the Gates foundation, the diseases they carry kill about 725,000 people a year, 600,000 of them victims of malaria. They are, as such, the only creature responsible for the deaths of more humans than humans themselves; we only manage to kill about 475,000 a year. This deadly work is carried out all over the planet: mosquitoes are found on every continent except Antarctica. And now there is Zika, which can lead to microcephaly and its associated physical deformities in unborn children, and for which there is no vaccine. This new horror has prompted fresh attention to the vexed question of how to defeat them. And that consideration leads to an unsentimental thought that we would entertain about no other creature: can’t we wipe them off the face of the Earth?
“I don’t think most people would have any qualms about totally eliminating them,” says Professor Hilary Ranson, head of vector biology at the Liverpool School of Tropical Medicine. “I spend most of my time trying to keep them alive and study them, but that’s in order to try to kill them. Ultimately I wouldn’t be too sentimental.” Professor Steve Lindsay, a public-health entomologist at the University of Durham agrees: “I have no problem with taking out the mosquito.”
In reality, as Lindsay and Ranson are quick to point out, the total extinction of all mosquito species would be as senseless as it would be impossible. Of the 3,000 varieties on the planet, only 200 or so bite us; only Aedes aegypti, and perhaps the more common Culex quinquefasciatus, are thought to carry Zika. Besides, as Jules Pretty, professor of environment and society at the University of Essex, points out: “In lots of environments, especially the Arctic north, where their abundance is utterly dispiriting, they are a vital source of food for animals higher up the food chain.” A total mosquito apocalypse would be a catastrophe. (…)