Genetically modified mosquitoes could stop dengue fever spreading (Image: Sergio Moraes/Reuters)

Mozzies in Brazil could soon be dropping like flies. On 10 April, Brazil became the first country to approve the commercial use of genetically modified insects when it gave the green light to GM mosquitoes designed to control the spread of dengue fever.

Dengue fever affects more than 50 million people worldwide every year and can be deadly. Now biotech firm Oxitec of Oxford, UK, has genetically engineered males of the species Aedes aegypti so that their offspring die before reaching maturity. If released GM males mate with enough females, a population crash should ensue, dramatically reducing the chance they will pass the dengue virus to humans.

Field trials of GM insect control have been under way for some time, including a recent test of Oxitec’s mosquitoes in the Brazilian city of Jacobina, where mosquito populations plummeted by 79 per cent between June and December last year, the company claims. In the US, where dengue has recently begun to reappear, the insects are up for approval by the Food and Drug Administration.


Thomas Scott, an entomologist at the University of California, Davis, says the modified mosquitoes could help, but that the main problem with dengue control is that the traditional method of spraying insecticide often isn’t done correctly. “If you look at most endemic areas, people aren’t doing larval control thoroughly enough,” he says. “By the time someone is sick, the virus has gone far beyond the 100 metres they spray around the house.”

Blanketing a country the size of Brazil with GM mosquitoes would also be prohibitively expensive, he adds. But for targeted control on the scale of towns and small cities, the modified insects could prove to be a useful tool.