Scientists in the US have succeeded in genetically engineering a malaria-resistant mosquito.The researchers, from the University of Arizona, introduced a gene that affected the insect's gut, meaning the malaria parasite could not develop.They report the advance, which also reduced the insects' lifespan, in the journal PLoS Pathogens.They say that the ultimate goal is to introduce malaria-resistant mosquitoes into the environment."Before we do this, we have to somehow give the mosquitoes a competitive advantage over the disease-carrying insects," explained Professor Michael Riehle from the University of Arizona a principle investigator on the project.In the study the researchers altered a gene that codes for a "signalling molecule".This molecule, a protein, enables the mosquito's cells to communicate with each other, and is crucial for parasite development inside the mosquito.The genetic tweak artificially increased its production, disrupting the whole process, and also shortened the insect's lifespan.The team was able to add a fluorescent tag to the gene, to ensure that it had been successfully "expressed" by the mosquito larvae.Professor Riehle said: "This is the first time that we've been able to completely block the parasite from developing in the mosquito."Gareth Lycett, a malaria researcher from Liverpool School of Tropical Medicine in the UK, said it was an important advance."They have tested it on the most harmful of the malaria parasites, Plasmodium falciparum," he told BBC News. "It is another step on the journey towards potentially assisting malaria control through GM mosquito release."But Dr Lycett pointed out that the this work had not been carried out specifically on the Anopheles gambiae mosquito. "That is the major vector of malaria in Africa where the disease is most prevalent," he explained.This study was a collaborative project with the University of California Davis and the University of Georgia funded by the National Institutes of Health.