DEADLY 鈥榮uper mosquitoes that are even tougher鈥� accidentally created by scientists after bungled experiment,鈥� shouted The Sun in the UK. 鈥淧lan to kill off mosquitoes backfires, spawning mutant hybrid insects,鈥� screamed the New York Post in the US.
These headlines appeared last month, in response to a carried out in Brazil from 2013 to 2015. It released millions of genetically modified male Aedes aegypti mosquitoes, which transmit serious diseases such as dengue, yellow fever, Zika and chikungunya. The mosquitoes carried an added gene meant to kill their offspring and thus wipe out wild mosquitoes.
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The shocking headlines aren鈥檛 true, but do contain an element of truth. We have created mutant mosquitoes, but not because of any genetic engineering mishap.
That story begins in West African forests a few thousand years ago. There, female A. aegypti xdrank the blood of many species. Over time, these mosquitoes evolved a separate subspecies that fed on humans. In the 15th century, . From there, they reached every tropical region, allowing diseases like yellow fever to spread to these places too. Now, these mosquitoes are developing resistance to the pesticides we rely on to control them.
Such is the backdrop for the Brazil trial, led by a company called Oxitec. It is true that the 鈥渓ethal鈥� gene fails to kill up to 5 per cent of the offspring of released males and wild females. Oxitec says .
It is also true that the males derive from Cuba and Mexico, so the survival of a small percentage of their offspring creates a mix of three closely related strains of the same A. aegypti subspecies. Yet calling these hybrids is a stretch, and there is no reason to think they pose a greater threat, as some have claimed.
The trial also didn鈥檛 fail: it reduced numbers of A. aegypti in the city of Jacobina by at least 70 per cent. When the releases stopped, the wild mosquitoes began to rebound, as predicted.
The story of A. aegypti is no one-off. Alter the environment and you alter the DNA of the creatures that live in it. The massive changes we are making to the planet are causing all sorts of mutant monsters to evolve 鈥� from antibiotic-resistant superbugs to poison-resistant rats and bedbugs.
Genetic engineering is one of our best hopes of controlling these mutants we are inadvertently creating. There are, of course, risks. In the US, pollen from trial plots of glyphosate-resistant GM bentgrass for use on golf courses spread to wild bentgrass in 2003. Earlier this year, it emerged that dairy cattle supposed to have only a tiny DNA change to make them hornless .
But herbicide-resistant wild grass is only a problem for those who rely on herbicides to kill grass. Hundreds of wild plants have already evolved resistance without added genes. And cows with an antibiotic-resistance gene wouldn鈥檛 be a major issue, even if regulators hadn鈥檛 detected them in time: antibiotic resistance stems mainly from antibiotic overuse for both people and animals.
The key question is whether the benefits of genetic engineering outweigh the risks. I am not convinced that making it easier to maintain golf courses is a good enough reason, but hornless cattle would make the painful methods used to dehorn calves redundant.
As for controlling mosquitoes, it is unclear whether Oxitec鈥檚 approach and others like it are practical. But surely it is worth trying them to prevent diseases like Zika 鈥� which can cause serious birth defects 鈥� and judging the results objectively rather than spreading scare stories.
Michael Le Page is an environment reporter for New Scientist
