Saturday science subject: The biopesticide

— 11:09 AM on January 3, 2009

What if you could nearly eradicate a tropical disease without wiping out the species of mosquito that carries it? According to Nature, a team of Australian researchers may have found a way to do just that with dengue fever, a disease that allegedly kills roughly 12,500 people a year in countries like Brazil, India, Malaysia, Mexico, Singapore, and Taiwan.

Scott O'Neill, a geneticist at the University of Queensland in Brisbane, Australia, and his team has now developed a way to kill the mosquitoes before the dengue virus is mature enough to infect people if they are bitten. Dengue fever takes approximately 8–10 days to incubate in mosquitoes, and therefore tends to be spread by older insects.

The team used a strain of the insect-infecting Wolbachia pipientis bacterium, which usually infects fruit flies and causes them to die early. By adapting the bacterium to infect A. aegytpi, the team hoped to cut the mosquito's lifespan.

After unsuccessful attempts to infect the dengue fever mosquitoes with the naturally occurring form of W. pipientis, the team grew the bacteria in a culture with the mosquito cells. Over a period of three years, some of the bacteria adapted so that they could successfully infect two female mosquitoes.

The bacteria shorten the Aedes aegypti mosquito's life span from 60 to 30 days, which could be enough to reduce dengue virus transmission to zero—assuming the bacteria infect mosquitoes in the wild, that is. To see whether that's possible, Nature says the team has kicked off field studies with caged mosquitoes. The approach may not succeed if the bacteria don't shorten wild mosquitoes' lives by a sufficient amount, or if the dengue virus adapts to infect mosquitoes quicker.

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