The genetic diversity of the hosts responsible for the majority of malaria transmission in Africa, Anopheles gambiae and Anopheles coluzzii mosquitoes, is presented in a study published online in Nature this week. A better molecular understanding of the genetics of these species is essential to maximize the lifespan of insecticides, and to accelerate the development of new strategies for vector control.

Substantial reductions in malaria morbidity and mortality have been achieved through the use of insecticide-based interventions, but increasing levels of insecticide resistance and other adaptive changes in mosquito populations threaten to reverse these gains.

As part of the Anopheles gambiae 1000 Genome Project, Alistair Miles and colleagues sequenced the genomes of 765 specimens of Anopheles gambiae and Anopheles coluzzii from 15 locations across 8 African countries spanning a range of ecologies including rainforest, inland savannah and coastal biomes. The authors found that the genomes of individual mosquitoes carried between 1.7 and 2.7 million variant alleles, confirming that they are among the most genetically diverse eukaryotic species. They also found signals of recent positive selection in several genes that are known to have a role in insecticide resistance. For example, a mutation known as ‘kdr’ in the gene Vgsc reduces susceptibility to the insecticides DDT and pyrethroids.

The authors argue that the design of mosquito controls should take into account the high levels of genetic diversity in mosquito populations.