Mosquitoes can be genetically modified to resist being infected by the virus that causes dengue fever, say researchers.

It is the first time that scientists have bred mosquitoes that not only resist 'type 2' dengue virus — the most prevalent strain — but also pass this resistance on to their offspring.

Dengue fever is spread through the bite of the Aedes aegypti mosquito. Each year, the virus kills about 20,000 of the 50 million people it infects across the developing world.

The researchers say that releasing the genetically modified (GM) mosquitoes could help prevent people from catching the disease as the mosquitoes would no longer be able to transmit the virus.

They add, though, that much more research is needed before this can happen.

The team, led by Ken Olson of Colorado State University in the United States, published their findings yesterday (13 March) in Proceedings of the National Academy of Sciences.

Olson and colleagues modified Aedes aegypti mosquitoes to trigger a mechanism that destroys the virus when it enters their midgut.

If the approach could be reproduced in wild mosquitoes, the incidence of dengue fever in humans could be reduced as fewer insects would transmit the virus.

However, much more research is needed before the method can be applied or even tested outside the lab.

Olson told SciDev.Net that the researchers now want to improve their method, as it currently only works for one of the four strains of the virus.

The researchers will also explore ways of getting the inserted gene to spread through wild populations, something that mosquito expert Peter Atkinson, of the University of California at Riverside in the United States, believes could be a challenge.

Olson says his team has no plans to release GM mosquitoes into the wild at this stage.

Link to abstract of paper in Proceedings of the National Academy of Sciences

Reference: PNAS 103, 4198 (2006)