For a large portion of the world, particularly sub-Saharan Africa, the buzz of mosquitoes carries with it the threat of malaria. The disease, caused by the plasmodium parasite, infects hundreds of millions of people annually and kills nearly a million. Anti-malarial drugs can prevent the disease from becoming fatal, but parasites can grow resistant to their effects. "Many researchers focus on the direct effects of plasmodium on the human body but the mosquito is an equally important battleground in fighting the disease," notes Fotis C. Kafatos of the European Molecular Biology Laboratory. In a report published today in the journal Science, his team describes three genes that could help scientists employ the insect¿s own immune system to stop malaria¿s spread.

Kafatos and his colleagues identified three mosquito immune genes that can affect the parasite¿s life cycle within the mosquito species (Anopheles gambiae) that transmits most cases of malaria in Africa . Two of these genes, dubbed CTL4 and CTLMA2, encode proteins that seem to safeguard the developing parasites. When the scientists silenced them, the mosquitoes¿ immune systems destroyed up to 97 percent of the maturing parasites. The third gene, LRIM1, has the opposite effect: mosquitoes lacking LRIM1 produced more parasites than their normal counterparts did.

"These studies are the first to show the power of the mosquito¿s immune system and give us some very real options for fighting the disease in the insect before it even has a chance to be passed to a human," Kafatos comments. The authors of an accompanying commentary, Janet Hemingway and Alister Craig of the Liverpool School of Tropical Medicine, agree that the results are encouraging, but note that they are just a small initial step toward new treatments. The findings, they write, "give cause for optimism that new methods of malaria control through blocking transmission in the mosquito vector will be possible."

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