Malarial mosquitoes turning into new species

Two strains of the mosquito responsible for most malaria transmission in Africa are evolving into different species, meaning that techniques to control them may work on one type but not the other.

Researchers from Imperial College London looked at two strains of the Anopheles gambiae mosquito, known as M and S.

And while they’re physically identical, the new research shows that their genetic differences are becoming so great that they are on the road to becoming different species. This means that control techniques such as creating new insecticides or trying to interfere with their ability to reproduce need to be effective in both strains.

And as the research suggests that mosquitoes are evolving more quickly than previously thought, scientists will need to monitor the genetic makeup of different strains very closely.

“Unfortunately, strategies that might work against one strain of mosquito might not be effective against another,” says Imperial’s Dr Mara Lawniczak. “It’s important to identify and monitor these hidden genetic changes in mosquitoes if we are to succeed in bringing malaria under control by targeting mosquitoes.”

In two studies, the researchers carried out the most detailed analysis so far of the genomes of the two strains. The first, which sequenced the genomes of both strains, revealed that M and S are genetically very different and that these genetic differences are scattered around the entire genome. Previous studies had only detected a few ‘hot spots’ of divergence between the genomes of the two strains.

In the second study, the researchers looked at many individual mosquitoes from the M and S strains, as well as a strain called Bamako, and compared 400,000 different points in their genomes where genetic variations had been identified. The results showed that the strains appear to be evolving differently, probably in response to factors in their specific environments.

Following these findings up, the Imperial researchers are now carrying out genome-wide association studies of mosquitoes, using the specially designed genotyping chip that they designed for their second study. They want to explore which variations in mosquito genes make them most likely to become infected with malaria and other pathogens.