Killer Mosquitoes Hunted Down with Their Own Genes

Did you know that scientists consider that the animal that kills most people is... the mosquito!? That's because mosquito-transmitted malaria kills annually 1.5 million people, mainly African children, not to mention the victims of yellow and dengue fevers. Now an international team has mapped the genes that constitute the immune system of the Aedes aegypti mosquito, the vector of the yellow and dengue fevers.

The mosquito's immune system is involved in controlling the transmission of viruses behind yellow and dengue fevers, which infect over 50 million people worldwide annually (malaria infects 500 million people annually!). Over 350 genes linked to the Aedes mosquito's immune system were found, and they had a faster evolving rhythm than the rest of the mosquito's genes had.

Detecting which of these genes are involved in the transmission of viruses may lead to the development of new methods of fighting these diseases. If mosquitoes are helped to fight off the viruses, the transmission to humans would be largely cut off. The same team had previously found that other mosquito types have a robust immune system that blocks transmission of malaria parasites; that's why only the Anopheles mosquitoes can spread malaria.

"By working to understand as much as possible about these genes, and the way they interact with specific pathogens, we hope to gain a more complete understanding of the mechanisms by which a pathogen either survives inside the insect body, or is killed by the insect's defenses." said senior author Dr George Christophides of Imperial's Division of Cell and Molecular Biology.

The team compared the immunity genes of the Aedes mosquito with those found in the fruit fly and the Anopheles mosquito. The two different mosquitoes presented some similarities in their immune genes, but also many differences, that could explain why Aedes transmits dengue and yellow fevers, while Anopheles transmits malaria.

"This study made us realize that the immune systems of insects are not static but evolve and differentiate rapidly, most likely in response to the different pathogens which each insect species encounters", said Christophides.