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A race is on to do something about the Zika virus. A possible vaccine is years away, so that means doing something about its vector, the Aedes aegypti mosquito.
Genetic engineering techniques mean it is possible to . But would there be an ecological downside to exterminating a creature whose only purpose seems to be to bother us?
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As with many predictions involving complex natural systems, a definitive answer is impossible. Some ecologists worry about small changes having big unforeseen effects, and liken the complexity of ecosystems to that of an aircraft. Removing the odd rivet may seem harmless… until it suddenly falls out of the sky.
But in reality, ecosystems seem to be mostly more resilient than planes. And nobody has come up with a key ecological job done by mosquitoes that .
In addition, the world is full of examples of local mosquito eradications that have not brought ecological meltdown. Where there has been damage to other species, it tends to be a by-product of the method used – draining marshes or spraying insecticides – rather than the loss of the insects themselves.
Mosquitoes are undoubtedly a plague. There are more than 3500 species buzzing away from the Arctic to tropical swamps, bringing yellow fever, dengue fever, Japanese encephalitis, Rift Valley fever, West Nile virus and now Zika. So, if there is no strong ecological case for keeping them, why not try to exterminate them?
Right now the leading plan for tackling Zika in Brazil is to flood populations of Aedes with males engineered to contain a lethal gene that kills their offspring, causing the population to crash. The technology has been used in the north-east of the country since 2011 in an attempt to control another disease Aedes carries, Dengue fever.
Similar methods of eradication have tackled various other insects. Notably the , which swamps populations with sterile males, and has been used in the Americas to fight the Mediterranean fruit fly and the screw worm.
Back in 2002, the International Atomic Energy Agency took me to east Africa to see how releasing male tsetse flies irradiated to make them sterile had from the island of Zanzibar, and with them trypanosomes, the parasite they spread that brings debilitating to humans and death to cattle. It worked but it wasn’t easy; it took $5 million and 8 million sterile males to eradicate Zanzibar’s 10, 000 flies. Fears of a wider effect on biodiversity .
Well before this, in the late 1950s, the world may have come close to eradicating malaria by targeting its host, the Anopheles mosquito, by spraying the insecticide DDT wherever it lived, before concerns about wider toxicity to wildlife saw its use curbed. The mosquitoes and the disease returned.
Nobody should under-estimate the difficulty of fighting one of the world’s most successful insects. But it is worth remembering that once, despite concerns about nature’s fragility, we nearly did for them.
Fred Pearce is a consultant for ¿ìè¶ÌÊÓƵ
