Destined to die: the offspring of the genetically modified mosquitoes die as larvae

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Denying Aedes aegypti mosquitoes the chance to be parents could potentially curb dengue fever — but environmentalists are wary of the risks involved.

Dengue fever is a debilitating, sometimes fatal disease that affects more than 100 million people in 100 countries. It has no cure so scientists are turning to genetically modified (GM) mosquitoes.

A strategy devised at Oxford University, United Kingdom, involves inserting a gene into male A.aegypti that causes their offspring to die as larvae.

The plan is to release a swarm of GM males into the wild and await the A.aegypti population's decline. The idea has only recently gained widespread support, most notably from the Bill and Melinda Gates Foundation which has invested US$38 million in the research.

But critics disapprove of such interference with the world's ecosystems, describing it as "arrogant". Others have pointed out that some mosquito-borne diseases, such as malaria, do not need this kind of approach because they can already be prevented and treated.

Supporters, however, say the technology could save millions of lives in the developing world.

"If you are sitting with your pregnant wife in a hospital in Tanzania or Malawi, then you are not going to be so worried about the escape of a few mosquitoes," says Arthur Caplan at the University of Pennsylvania, United States.

The WHO is developing strict protocols for testing GM mosquitoes. And researchers say they are committed to taking "an extraordinarily cautious approach".