Genomic studies reveal human influence on mosquito evolution and disease spread

Two of the world's deadliest mosquito vectors – Aedes aegypti and Anopheles funestus – have evolved, spread, and adapted in ways that complicate global disease control, two studies show. The findings trace the human-linked origins of Ae. aegypti's invasive lineage. They also reveal the rapid emergence of insecticide resistance in An. funestus. Collectively, they reveal the urgent need for more tailored and innovative interventions against malaria and dengue. Top of Form"Both [studies] provide important insights into the … the complex role that human activity, both passive and intentional, plays in their movement and adaptations," writes Tamar Carter in a related Perspective. "These processes have led to complex subspecies genomic diversity that likely translates to functional diversity that is yet to be fully elucidated." Bottom of Form Mosquito vector-borne diseases represent a major global health challenge, with malaria and dengue each causing hundreds of millions of infections annually, worldwide. The increasing mobility of people and goods has enabled mosquitoes, once confined to relatively narrow regions, to spread widely and adapt to new environments. Although modern genomic analyses could provide insight into the origin, evolution, spread, and control of these vectors, individual mosquito species are unequally represented in studies. Here, in a pair of studies, researchers analyze genomic data from Ae. aegypti and An. funestus mosquitoes to reconstruct their evolutionary and demographic histories.

In one study, Jacob Crawford and colleagues investigated Ae. aegypti – the primary vector of dengue, chikungunya, and Zika. The precise origin of the globally invasive Ae. aegypti has long been debated. Crawford et al. sequenced 1206 genomes from 73 globally distributed populations, using coalescent and phylogenetic analyses to disentangle ancient from recent migration events. According to the findings, after evolving a preference for humans in West Africa, Ae. Aegypti made its way to the Americas during the Atlantic slave trade, with the globally invasive lineage ultimately arising in the Americas. More recently, this invasive lineage has re-entered Africa and interbred with native populations, coinciding with increased dengue outbreaks and the spread of insecticide-resistance mutations.

In another study, Marilou Boddé and colleagues performed a sweeping genomic analysis of An. funestus to investigate how this major malaria vector has adapted, particularly under vector control pressure. Boddé et al. sequenced 701 modern and historic An. Funestus mosquitoes from 16 African countries. The findings revealed a complex population structure – while some populations showed strong geographic structuring, others were genetically connected across wide distances, with distinct lineages emerging in places like North Ghana and South Benin. According to the authors, this diversity suggests that uniform control strategies are unlikely to succeed, emphasizing the need for locally tailored interventions. Moreover, by comparing modern samples with century-old museum specimens, the team showed that insecticide resistance arose both through independent mutations and the spread of resistant lineages. Most insecticide resistant variants found in modern An. Funestus were not found in historical species from as recent as 1967, suggesting rapid emergence. Boddé et al. also discovered promising gene drive targets within An. Funestus, which could enable more effective and strategic vector control efforts.