Saturday, January 3, 2009

Scientists hope to prevent malaria by cutting lifespan of mosquitoes

Interesting idea, though I'm not entirely comfortable with it:
Old mosquitoes usually spread disease, so Australian researchers figured out a way to make the pests die younger - naturally, not poisoned.

Scientists have been racing to genetically engineer mosquitoes to become resistant to diseases like malaria and dengue fever that plague millions around the world, as an alternative to mass spraying of insecticides.

A new report Friday suggested a potentially less complicated approach: breeding mosquitoes to carry an insect parasite that causes earlier death.

Once a mosquito encounters dengue or malaria, it takes roughly two weeks of incubation before the insect can spread that pathogen by biting someone, meaning older mosquitoes are the more dangerous ones.

The Australian scientists knew that one type of fruit fly often is infected with a strain of bacterial parasite that cuts its lifespan in half.

So they infected the mosquito species that spreads dengue fever - called Aedes aegypti - with that fruit-fly parasite, breeding several generations in a tightly controlled laboratory.

Mosquitoes born with the parasite lived only 21 days - even in cosy lab conditions - compared with 50 days for regular mosquitoes, University of Queensland biologist Scott O'Neill reported in the journal Science.

Mosquitoes tend to die sooner in the wild than in a lab. So if the parasite could spread widely enough among these mosquitoes, it "may provide an inexpensive approach to dengue control," O'Neill concluded.

Theoretically, it could spread: This bacterium, called Wolbachia, is quite common among arthropod species, including some mosquito types - just not the specific types that spread dengue and malaria, the researchers noted. And Wolbachia strains are inherited only through infected mothers, with an evolutionary quirk that can help them quickly gain a foothold in a new population.

From the Woodstock Sentinel-Review. Certainly it seems less disruptive than the proposal to completely exterminate all Anopheles mosquitoes by introducing harmful segregation distorters to the insects' genomes, though engineering a significant change in the life cycles of wild populations is not something to be taken lightly even if extermination is not your goal. But maybe the benefits do outweigh the costs; certainly malaria is a grave problem throughout much of the world, and it may become worse as global warming opens up new habitat to the mosquitoes that carry it.

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