Shortening mosquito lifespan could tackle dengue

Aedes aegypti, the dengue carrier mosquito Copyright: CDC

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Scientists seeking new ways of tackling dengue fever have found they can halve the lifespan of its carrier mosquito — leaving it no time to transmit the disease.

The work could open a new route to tackling not just dengue but also malaria. But there are practical and ecological obstacles.

The researchers infected a group of Aedes aegypti mosquitoes with a strain of bacteria that killed them before they became old enough to pass the dengue virus to humans.

It takes around two weeks for a mosquito to transmit dengue fever because the virus needs time to develop in its host.

The team, at the University of Queensland, Australia, used a strain of Wolbachia bacteria. Wolbachia is a common insect pathogen already known to shorten the lifespan of fruit flies, but it does not naturally infect A. aegypti.

The scientists modified the strain and on injecting it into A. aegypti, found that none of them lived beyond two weeks.

The bacteria are a good candidate for mosquito control because of their ability to spread through mosquito populations, says Andrew Read, professor of biology and entomology at Penn State University in the United States, who wrote a perspective article on the research in Science.

Unlike insecticides, which require regular reapplication, the bacteria would need to be injected only once, he said.

"That’s what’s exciting about this idea. In principle, Wolbachia can drive themselves through a population so that in the end all of the mosquitoes would be infected," Read told SciDev.Net.

The laboratory-based work must now be replicated outdoors. But it might be impossible to test the impact on human disease without releasing infected mosquitoes irrevocably into the wild, he says.

"The science will take about 3–5 years. The regulatory issues — getting permission to release [the mosquitoes] — I don’t know how long that will take."

It might be easier to field-test the technique as a tool for malaria control, because there are suitable isolated populations of infected people where a pilot study could be contained.

But there are several reasons why the strategy might not work in the long term. "Would the bacteria evolve to become nice, would the dengue evolve to develop more rapidly? It could be a transient effect, and evolution will unravel the effect of Wolbachia just as it unravelled insecticides."

The research was published this month (2 January) in Science.


Science 323, 141 (2008)
Science 323, 51 (2008)