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Pests' Pests: Parasite may help stop spread of disease
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The Aedes aegypti mosquito is known to spread dengue fever. Scientists are hoping to shorten its life span.
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Published: January 2, 2009
WASHINGTON
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 such as malaria and dengue fever that plague millions around the world, as an alternative to mass spraying of insecticides.
A new report today 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 about two weeks of incubation before the insect can spread that pathogen by biting someone, meaning that older mosquitoes are the more dangerous ones.
The Australian scientists knew that one type of fruit fly is often infected with a strain of bacterial parasite that cuts its lifespan in half.
So they infected the mosquito species that spreads dengue fever -- Aedes aegypti -- with that fruit-fly parasite, breeding several generations in a tightly controlled laboratory.
Voila: Mosquitoes born with the parasite lived just 21 days -- even in cozy 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, Wolbachia, is quite common among arthropod species, including some mosquito types -- just not the specific types that spread dengue and malaria, the researchers said. Wolbachia strains are inherited only through infected mothers, with an evolutionary quirk that can help them quickly gain a foothold in a new population.
Next month, O'Neill's team will begin longer studies in special North Queensland mosquito centers that better mimic natural conditions to see how well the wMelPop strain persists as more mosquitoes are born, and what happens when they are exposed to dengue.
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