Tuesday, March 01, 2011

Up Malaria's Sleeve

And why bed nets don't quite do the trick

The primary vector of malaria to humans has long been known to be the Anopheles gambiae mosquito. When one bites a human it transmit the parasite Plasmodium falciparum, and that's what hosts the virus. The insects bite mostly when inside human dwellings. Hence, malaria control methods rely heavily on the indoor use of insecticides and on bed nets.

Despite best efforts, however, malaria continues to infect about 250 million people a year and kill about a million. In the February 3 issue of Science a team lead by parasitologist Ken Vernick of the Pasteur Institute in Paris reports the discovery of a subtype of A. gambiae that may account for some of the continuing high rate of infection. Mosquitoes of this subtype--known as Goundry, for the African village in the country of Burkina Faso in which Vernick's team found it--live outdoors, and they seem to be particularly dangerous. Goundry are more susceptible than indoor-living A. gambiae to Plasmodium, acquiring infection 23% more frequently when feeding on malaria-infected blood.

Vernick and colleagues have yet to find adult Goundry in the wild. What they discovered outdoors were larvae, which they hatched in the lab, raised to adulthood, genetically tested, and used in infection experiments. Possibilities for population control of Goundry include traditional methods like wide-spread fogging, and newer, chemical-free approaches like the release into the wild of genetically engineered sterile males.

Sterile insect technology has problems above and beyond push-back from a public afraid of "Jurassic Park" insects. How do you breed a bug to be both sterile and hardy? Sterile and sexy? How do you track the insects? (There are no physiological markers identifying them as sterile.) These are issues pressuring not only scientists who combat disease-carrying mosquitoes but those fighting agricultural pests like fruit flies, coddling moths, and pink bollworms, as well.

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