'Want to Stop Malaria? Target the Geezers'

A new paper suggests that the current strategy for killing mosquitoes carrying malaria that has been used for the past fifty years may be less efficient than previously thought. The way things are done at the moment, mosquitoes are killed quickly while they are young in order to prevent the spread of malaria, but recent research has shown that by using types of insecticides that act more slowly, killing older mosquitoes, pesticide resistance may be minimized. The evolution of pesticide resistance is a problem in controlling the spread of the disease because the mosquitoes are able to build up immunities and spread the parasite despite preventative measures.

In areas where spraying takes place, certain gene mutations in mosquito larvae that give even slight resistance are spread quickly due to their usefulness. Pesticides have gradually become ineffective against the spread of malaria due to this buildup of immunities and resistances to them and now pose a growing problem in preventing the disease as the alternative number of pesticides begins to dwindle.

This new research deals with the problem of resistance because insecticides that kill mosquitoes early on in life prevent the act of reproduction altogether, which puts a great deal of pressure on the species to become resistant. Mosquitoes, however, are only able to spread malaria once they are around 10 to 14 days old, so it isn't necessary to put this much selective pressure on them. As long as malaria spread is prevented, the mosquitoes can be killed later in life, and thus be given more of a chance to reproduce without developing resistances. Models presented by the research have shown that the targeting of older mosquitoes would perhaps delay the emergence of pesticide resistance by decades and remain just as effective.

There are plenty of insecticidal candidates for this idea, including a slow-acting fungus, and the use of these in addition to applying them in certain combinations with each other should be extremely effective in preventing resistances for very long periods of time.

EDIT: One issue that was raised in the article was indeed the difficulty in suggesting this new method of mosquito-removal to potential buyers. It would be difficult to explain to a man who paid to have mosquitos killed that they would still be around for a while although malaria would be prevented.

(Nicholas Skvir, Group C)
http://sciencenow.sciencemag.org/cgi/content/full/2009/407/2