The study focused on the Anopheles gambiae species complex, a group of morphologically identical mosquitoes that includes the most efficient malaria vectors in Africa. Within Burkina Faso, the dominant vectors are Anopheles coluzzii and Anopheles gambiae sensu stricto, alongside Anopheles arabiensis. Understanding whether these populations are genetically divided by geography is far from an academic question. If mosquito populations in different regions are genetically isolated, a control tool introduced in one place may fail to spread or may need to be tailored separately for each region. Conversely, if mosquitoes mix freely across the country, a single intervention could, in principle, ripple outward through the entire population.

To answer this question, the researchers collected mosquito specimens across three ecological settings in Burkina Faso using pyrethroid spray catches, the standard method for sampling indoor-resting mosquitoes. The whole genomes of the captured Anopheles gambiae sensu lato specimens were then sequenced under the Ag1000G framework, a major international effort to catalogue genomic variation in African malaria vectors. The team analysed the resulting data using MalariaGEN resources, applying tools such as principal component analysis, ancestry-informative markers, pairwise genetic differentiation measures and neighbour joining trees to dissect the structure of the populations at single nucleotide polymorphism resolution.

The headline result is striking: neither Anopheles coluzzii nor Anopheles gambiae sensu stricto showed any detectable geographical population structure across the three climatic zones sampled. Mosquitoes from the Soudanian south and the Sahelian north of the country were, genomically speaking, members of the same interbreeding populations. This pattern points to high levels of gene flow within Burkina Faso, meaning mosquitoes are moving, or their genes are moving, across ecological boundaries at a rate sufficient to erase any regional genetic fingerprints. For two species that thrive in such different environments, the absence of differentiation is a powerful testament to their mobility and adaptability.

Anopheles arabiensis told a different story. This species displayed a weak but real structure that separated samples from the Hauts-Bassins region in the Soudanian zone from all other An. arabiensis samples in the study. In other words, while most of the country’s An. arabiensis mosquitoes appear well mixed, a distinct genetic signature sets the Hauts-Bassins population apart. The authors suggest this could reflect a distinct demographic history for that population. Indeed, their diversity analyses revealed evidence that An. arabiensis populations have undergone either a reduction in effective population size or a bottleneck, in contrast to the signals of population expansion observed across An. gambiae sensu lato more broadly.

The genomic toolkit behind these conclusions deserves attention. Nucleotide diversity and Watterson’s theta, two complementary estimators of genetic variation, were computed for each population, alongside Tajima’s D, a statistic sensitive to changes in population size. Heterozygosity was mapped across chromosome 3R in windows of ten thousand base pairs, allowing the team to examine variation at fine scale. Principal component analyses were performed both across the full dataset and per year, and pairwise differentiation was calculated within each species per region. The consistency of these independent lines of evidence strengthens the central claim that the two major vectors are panmictic, or freely interbreeding, across the country while An. arabiensis follows its own demographic trajectory.

One notable absence from the genomic data also caught the researchers’ attention. Two cryptic species, Anopheles goundry and Anopheles tengrela, previously identified within Burkina Faso, were not detected in this study. Cryptic species are lineages that look identical to their relatives but are genetically distinct, and their presence can complicate vector control because they may differ in behaviour, habitat preference or susceptibility to insecticides. Their non-detection in this nationwide sampling suggests these lineages are either rare, locally restricted or no longer circulating at detectable levels, though the authors are careful to frame this as an observation from the sampled specimens rather than proof of absence.

The implications for existing vector control are immediate. Long-lasting insecticidal nets and indoor residual spraying remain the backbone of malaria prevention in Burkina Faso, yet both are threatened by the expansion and persistence of insecticide resistance in vector populations. If resistance-conferring variants can move freely across the country through the same high gene flow documented here, then resistance management strategies, such as rotating insecticide classes or deploying new generation nets, may need to be coordinated nationally rather than regionally. A patchwork of local approaches could be undermined by mosquitoes or their genes arriving from neighbouring districts where a different insecticide is in use.

The implications for gene drive technology are even more profound. Gene drives are engineered genetic systems that bias inheritance so that a chosen trait, such as sterility or susceptibility to parasites, spreads rapidly through a wild population, even if the trait reduces the carrier’s reproductive fitness. The feasibility and safety of such systems depend critically on population structure. A drive released into a fragmented population might stall at genetic boundaries, limiting its effectiveness but also containing any unintended spread. The absence of geographical structure in An. coluzzii and An. gambiae sensu stricto within Burkina Faso suggests, by contrast, that a gene drive construct released in one part of the country could spread rapidly throughout the entire national population of these vectors. That is precisely the efficiency designers hope for, but it also underscores why containment modelling, staged testing and community engagement are central to the gene drive programmes now under development for malaria vector control in Africa.

The study was made possible by an unusually broad coalition. Sampling was carried out by the Institut de Recherche en Sciences de la Santé with the Ministry of Health of Burkina Faso and community health workers, and the work was funded by the Gates Foundation and Wellcome, which also support the safe and sustainable implementation of gene drive technology for malaria vector control in Africa. Genomic sequencing and analysis drew on the MalariaGEN Vector Observatory, an international collaboration building capacity for malaria vector genomic surveillance, with contributions from the Liverpool School of Tropical Medicine, the Broad Institute and the Wellcome Sanger Institute. For a country at the frontline of both malaria and mosquito innovation, the message of this research is clear: its two deadliest vectors behave, genetically, as a single connected population, and any strategy that hopes to outmanoeuvre them must think at national scale, while the more demographically fragile An. arabiensis may require a separate plan of its own.

Subject of Research: Population genomics of Anopheles gambiae complex malaria vectors in Burkina Faso and implications for gene drive implementation

Article Title: No geographical population structure of malaria vectors Anopheles gambiae and Anopheles coluzzii but weak structure in Anopheles arabiensis within Burkina Faso: implications for vector control and gene drive implementation

Article References: Kaboré, H., Brenas, J., Kientega, M., Traoré, N., Pescod, P., Sawadogo, G., Koutoucheva, A. H., Lanfrancotti, A., Namountougou, M., Maiga, H., Nolan, T., Miles, A., Clarkson, C. S., & Diabaté, A. (2026). No geographical population structure of malaria vectors Anopheles gambiae and Anopheles coluzzii but weak structure in Anopheles arabiensis within Burkina Faso: implications for vector control and gene drive implementation. BMC Genomics. https://doi.org/10.1186/s12864-026-13321-6

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13321-6

Keywords: Anopheles gambiae, Anopheles coluzzii, Anopheles arabiensis, malaria vectors, population structure, gene flow, gene drive, vector control, whole-genome sequencing, Burkina Faso, genetic diversity, insecticide resistance

The global malaria picture remains grim. In 2024, an estimated 282 million cases and 610,000 deaths were reported worldwide, an increase of nine million cases over the previous year. Sub-Saharan Africa bears roughly 94 percent of the global burden, and control efforts are increasingly threatened by insecticide-resistant vectors, parasites that evade rapid diagnostic tests, and the emergence of resistance to artemisinin-based combination therapies. Into this already fragile landscape has stepped An. stephensi, a vector native to the Indian subcontinent and the Persian Gulf that thrives in man-made water containers and urban environments, raising the specter of malaria re-emerging in African cities that had previously been relatively protected.

Since its detection in Djibouti, An. stephensi has been reported in Ethiopia in 2016, Sudan and Eritrea in 2019, Somalia in 2019, Nigeria in 2020, Yemen in 2021, Kenya and Ghana in 2022, and Niger in 2025. Reports have linked its introduction to malaria resurgence in Djibouti and Ethiopia, and modeling studies suggest that its expansion could expose vast urban populations to transmission risk. Yet a critical biological question remained unresolved: how efficiently does this Asian vector transmit African strains of P. falciparum, a parasite that evolved on the continent and adapted to a different suite of mosquito hosts during its global spread?

Earlier evidence had hinted at the answer. A 2021 study using direct membrane feeding assays found that An. stephensi was permissive to both P. vivax and P. falciparum relative to An. arabiensis, but the limited number of P. falciparum observations precluded firm conclusions. The new research, led by scientists at the Armauer Hansen Research Institute in Addis Ababa together with collaborators at Arba Minch University, Addis Ababa University, Radboud University Medical Center, the London School of Hygiene and Tropical Medicine, and Wollo University, was designed to close that gap with a robust, paired comparison focused specifically on the deadliest human malaria parasite.

The study was conducted in Metehara, a town in Oromia Regional State lying at roughly 947 meters above sea level along the major transportation corridor connecting Ethiopia with Djibouti, where An. stephensi has been established since 2019. Malaria transmission in the area is seasonal, peaking from August to December after the main rains, and P. falciparum accounts for about 75 percent of clinical infections. Between August 2024 and January 2025, the team recruited 43 patients with microscopy-confirmed P. falciparum gametocytes at two health centers, Dire Gobu and Haro Adi, collecting five-milliliter venous blood samples before participants received treatment with artemether-lumefantrine.

The mosquitoes themselves came from the Adama Malaria Research and Training Center, which has maintained An. arabiensis colonies since the 1970s and established an An. stephensi colony in April 2023. By the time the feeding assays began, the stephensi colony had reached its twenty-fifth generation. For each experiment, 120 three-to-five-day-old females of each species were starved for six to eight hours and then fed in parallel on the same patient blood through water-jacketed glass feeders maintained at 37 degrees Celsius. Ten days after feeding, mosquitoes were dissected and their midguts stained and examined under a microscope for oocysts, the developmental stage of the parasite that forms on the mosquito gut wall.

The results were striking in their symmetry. Feeding efficiency was the only measure in which the native vector clearly outperformed the invader: 85 percent of An. arabiensis took a full blood meal compared with 78.3 percent of An. stephensi, a difference the authors attribute to the longer history of laboratory adaptation in the arabiensis colony. But when it came to actual susceptibility, the two species were nearly indistinguishable. Roughly 68 to 70 percent of feeds on patient blood infected at least one mosquito of either species, and the proportion of dissected mosquitoes carrying oocysts was identical at 30.7 percent in both species. Infection rates in paired feedings were strongly correlated between the two colonies, with a Spearman correlation coefficient of 0.85.

Oocyst intensity told a similar story. The researchers counted nearly 20,000 oocysts in infected An. stephensi midguts and more than 28,000 in infected An. arabiensis midguts, with median densities of 13.5 and 26.3 oocysts per infected mosquito respectively, a difference that did not reach statistical significance. A Bland-Altman analysis confirmed that patient blood was equally infectious to both species, with no meaningful bias toward either one. In the subset of experiments with low oocyst prevalence, where microscopy is most prone to error, molecular testing of mosquito carcasses on day fourteen showed that both species could carry infections through to the sporozoite stage, the form that is infectious to humans, with 14.2 percent of An. stephensi and 10 percent of An. arabiensis testing positive.

The authors caution that their assays were conducted under controlled insectary conditions that do not capture the environmental variability mosquitoes face in nature, and that all blood donors were symptomatic patients with relatively high parasite densities. In sub-Saharan Africa, most onward transmission of P. falciparum is thought to arise from asymptomatic individuals carrying lower parasite burdens, so future work will need to test whether the equivalence between the two vectors holds under those more representative conditions. Gametocyte biology itself complicates such studies, since the transmissible stages take nine to twelve days to mature, making the recruitment of gametocyte-positive donors a considerable logistical challenge.

Nevertheless, the message for public health is clear. Anopheles stephensi, newly arrived in Africa, is as permissive to local P. falciparum strains as the continent’s established primary vector, meaning it can sustain transmission at equivalent levels under controlled conditions. Combined with its preference for urban habitats and its documented association with malaria resurgence in the Horn of Africa, the finding underscores the urgency of early surveillance and targeted vector control in cities across the continent before this invasive mosquito becomes fully entrenched in new ecological settings.

Subject of Research: Comparative susceptibility of invasive Anopheles stephensi and native Anopheles arabiensis mosquitoes to Plasmodium falciparum gametocytes in Ethiopia.

Article Title: Comparative permissiveness of Anopheles stephensi colony mosquito with an Anopheles arabiensis colony to Plasmodium falciparum gametocytes in Metehara, Ethiopia

Article References: Comparative permissiveness of Anopheles stephensi colony mosquito with an Anopheles arabiensis colony to Plasmodium falciparum gametocytes in Metehara, Ethiopia. (n.d.). https://doi.org/10.1186/s13071-026-07463-5

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07463-5

Keywords: Anopheles stephensi, Anopheles arabiensis, Plasmodium falciparum, malaria, Ethiopia, direct membrane feeding assay, vector competence, invasive mosquito species, oocyst density, sporozoite, malaria transmission, vector surveillance