Crucially, the genetic tweak involved did not appear to hinder the modified mosquitoes in any other way.On every measure of healthiness they performed as well as their wild counterparts.And even though they were firing blanks, they were still able to mate with females in the laboratory.Although the details are not fully understood, says Dr Montell, once female mosquitoes have mated a few times, they become less receptive to doing so again.Mating with an infertile male is therefore not only fruitless in itself, but should also leave a female less interested in unmodified males in future.Sure enough, a series of experiments conducted in cages suggested that releasing between five and six genetically modified males for each wild male was enough to cut the number of reproducing females by half.Upping that ratio to 15:1 dropped it by 80%.There is more work to do before field trials, says Dr Montell. But having established the principle, he is excited to see where the work might lead.That the target gene is found in both fruit flies and Aedes suggests it is likely to exist in other disease-carrying mosquitoes, too.And that the engineered males leave no offspring means fewer worries about any unintended consequences which might arise from releasing millions of genetically modified organisms into the environment.
