Genetic diversity of the African malaria vector, the Anopheles gambiae mosquito: evidence for recent selection in insecticide-resistant genes

This topic is very central to “gene-environment (GxE) interactions.” Plasmodium falciparum is the disease-causing protozoan parasite that causes the infectious disease MALARIA in humans and other primates (which are called “the host”), and the blood-sucking mosquito Anopheles gambiae species is the vector that transmits the blood-borne disease from one host to another future host. Treating the mosquito with various insecticides can prevent malaria in humans by killing the vector. Yet, the mosquito’s DNA is able to mutate (DNA alterations) and the mosquito’s epigenome is probably also able to “re-adjust” to such adversity (i.e. some drug that wants to kill the mosquito) in order to survive. And survival of the mosquito is what we humans and clinical medicine do not want to happen.

Substantial decreases in the incidence of malaria morbidity and mortality have been achieved by the use of insecticide-based interventions, but increasing levels of insecticide resistance, and other adaptive changes in mosquito populations, threaten to reverse these achievements. A better understanding of the molecular, ecological and evolutionary processes driving these changes is essential to maximize the active “beneficial duration” of existing insecticides, and to accelerate development of new strategies and tools for vector control. The Anopheles gambiae 1000 Genomes Project (Ag1000G; was established to provide a foundation for detailed investigation of mosquito genome variation and evolution.

Authors [see attached article] describe here the first phase of the project, which analyzed 765 wild-caught specimens of Anopheles gambiae sensu stricto and Anopheles coluzzii. These two species account for the majority of malaria transmission in Africa, and are morphologically indistinguishable and often sympatric (i.e. occurring within the same geographical area; overlapping in distribution), but are genetically distinct and differ in geographical range, larval ecology, behavior, and strategies for surviving the dry season. The specimens were collected at 15 locations across eight African countries, spanning a range of ecologies including rainforest, inland savannah and coastal biomes, and thus provide a broad sample in which to explore factors shaping mosquito population variation. To gain a deeper understanding of how mosquito populations are evolving, authors identified >50 million single nucleotide variants. They found complex population structure and patterns of gene flow –– with evidence of ancient expansions, recent bottlenecks, and local variation in effective population size. Strong signals of recent selection were observed in insecticide-resistance genes, with several sweeps spreading over large geographical distances and between species. The design of new tools for mosquito control, using gene-drive systems, will need to take into account the high levels of genetic diversity in natural mosquito populations.
Nature 7 Dec 2o17; 552: 96–100

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