Species distributed across heterogeneous environments often evolve locally adapted populations, but understanding how these persist in the presence of homogenizing gene flow remains puzzling. In Gabon, Anopheles coluzzii, a major African malaria mosquito, is found in various ecological settings, including urban areas, remote rural villages, and forested environments away from any human presence. This study investigates the genomic signatures of local adaptation in populations from distinct environments including the urban area of Libreville, and two proximate sites 10 km apart in the La Lopé National Park (LLP), a village and its sylvatic neighbourhood. Whole genome re-sequencing of 96 mosquitoes unveiled 5.9 million high-quality single nucleotide polymorphisms. Coalescent-based demographic analyses suggest an ∼12,000-year-old divergence between Libreville and La Lopé populations, followed by a secondary contact (∼4000 ybp) resulting in asymmetric effective gene flow. The urban population displayed reduced effective size, evidence of inbreeding, and strong selection pressures likely associated to insecticides or pollution present in urban settings, as suggested by the hard selective sweeps detected in genes involved in detoxification and insecticide resistance. In contrast, the two geographically proximate LLP populations showed larger effective sizes, and distinctive selective signals, notably soft-selective sweeps on the standing genetic variation. Although presumably neutral loci failed to discriminate between LLP populations, our findings support that microgeographic adaptation can swiftly emerge through selection on standing genetic variation despite gene flow. This study contributes to the growing understanding of evolution of populations in heterogeneous environments amid ongoing gene flow and how major malaria mosquitoes adapt to humans and its environment.

Climate change is recognized as a critical determinant of malaria transmission in the coming decades. This manuscript synthesizes testimonies from six African countries (Chad, Côte d’Ivoire, Democratic Republic of the Congo (DRC), Madagascar, Rwanda, and Senegal) highlighting how climate variability has recently influenced malaria epidemiology and how national malaria control programmes (NMCPs) are adapting. The correlation between changing patterns of rainfalls, floodings, and how they affect the expansion of mosquito vector habitats with malaria transmission has been reported. Adaptive strategies adopted by the NMCPs include integrating climate and health data, strengthening surveillance and establishing early warning systems, engaging and educating communities, promoting multisectoral collaboration, and leveraging technology and innovation. However, systemic barriers, such as limited data integration capacity, infrastructural deficits, behavioural factors, and financial constraints, continue to impede effective implementation of adaptive strategies. Addressing these barriers requires sustained political commitment, enhanced technical capacity, operational and implementation research, and long-term investment in climate-resilient health systems. The findings offer valuable insights for broader regional efforts to align malaria control strategies with climate change.

In Madagascar, the health burdens caused by West Nile virus (WNV) and Rift Valley Fever virus (RVFV) vary across regions, likely resulting from the variations of their vector capacity. This study aimed to assess the degree of vector-hots contact and to develop statistical models to identify factors influencing host preferences. Bimonthly mosquito collections were performed in 25 sites of Madagascar from February to October 2019. Engorged mosquitoes were collected from indoors and outdoors resting locations within each site. Blood meal identification was performed using host-specific PCRs. Generalised linear models were developed to explain host preferences of the two most abundant species. The origin of the blood meal of 1,177 engorged females belonging to ten species was analysed. Human and cattle were the dominant vertebrate hosts identified (respectively 44.86% and 44.52%), and pigs were rarely detected (< 1%). Models were developed for Culex antennatus and Culex quinquefasciatus. For these two species, host preference was driven by climatic and environmental factors, type of habitat, indoor/outdoor location, and number of available vertebrate hosts. This study provides an essential step towards an evidence-based determination of arbovirus transmission risk and suggests to explore the use of other tools to supplement indoor vector control in Madagascar.

We report a global survey of viral small RNAs (vsmRNAs) from >200 Aedes aegypti samples to identify many mosquito viruses that actively infect this prominent arboviral vector. Ae. aegypti viruses in the Americas are abundant, with some displaying geographical boundaries. Viruses infecting Asian Ae. aegypti are similar to those in the Americas and reveal the first wild example of dengue vsmRNAs. African Ae. aegypti display vsmRNAs from viruses unique to these African strains. Academic lab colonies generally lack viruses, yet two commercial strains are deeply infected by a tombus-like virus that is related to plant viruses. Comparing matched viral long RNAs to vsmRNAs reveal viral transcripts evading the mosquito RNA interference (RNAi) pathway. By infecting mosquito cells with Ae. aegypti homogenates, we generate stably infected cell lines which produce vsmRNAs that were comparable to native mosquito vsmRNA patterns. Lastly, we demonstrate that these stably infected mosquito cells producing vsmRNAs can exert gene silencing of reporters bearing viral sequence segments, providing a potential explanation for how Ae. aegypti can resist viral infections. This vsmRNA genomics approach in Ae. aegypti can add to existing vector surveillance approaches by discovering new viruses that persist in mosquito populations.

Insecticide use remains one of the most common strategies worldwide for controlling household pests and disease vectors, despite growing concerns over misuse, health risks, and the emergence of insecticide resistance. To document household insecticide use and flea infestation across a gradient of plague endemicity in Madagascar, we used a multidisciplinary approach. A descriptive household survey and an observational checklist were implemented with 422 respondents and combined with flea infestation assessment based on flea sampling from small mammals and candle traps. Household insecticide use was primarily reported for pest control (92.4%), mainly targeting fleas (70.3%) and was generally applied reactively rather than preventively. Even though males constituted the majority of respondents (85.0%), mothers are reported to play a primary role in insecticide application (41.4%) and in the purchase (48.2%) of chemical products. Overall, good insecticide practices were observed in 51.3% of households, although the difference between good and poor practice categories was not statistically significant (p = 0.83). Comprehensive understanding of household insecticide use is crucial to implement effective integrated pest management, optimize vector control strategies, minimize selective pressures driving resistance, and protect both human health and the environment.

Mosquito-borne diseases remain a major public health concern in sub-Saharan Africa, yet the ecological drivers of mosquito community structure in intra-urban environments are poorly understood. This study aimed to assess how habitat heterogeneity, seasonality, and environmental gradients shape mosquito communities in Franceville. A longitudinal survey was conducted from July 2023 to July 2024 using 10 CDC light traps deployed weekly for three consecutive nights. Mosquitoes were identified morphologically and environmental, climatic, and urban variables were recorded. Community structure was analysed using diversity indices, principal component analysis (PCA), canonical correspondence analysis (CCA), and Variation Partitioning (VarPar). Species sensitivity to environmental gradients was quantified, and variation partitioning was used to assess the relative contributions of predictor groups. A total of 6794 mosquitoes representing 24 species across 7 genera were collected. Community composition varied significantly across habitat and season, with higher diversity in forest-associated habitats and more even assemblages in savannah environments. Multivariate analyses revealed distinct ecological responses among genera: Anopheles species showed high sensitivity to environmental gradients, whereas dominant Culex species exhibited broad ecological tolerance. Aedes aegypti was associated with savannah habitats and the rainy periods, while Ae. albopictus displayed marked ecological plasticity. Variation partitioning indicated that environmental variables explained a larger share of community variation than climatic and urban predictors, with additional effects from their interactions. Mosquito communities in southeastern Gabon are primarily structured by fine-scale habit heterogeneity and seasonal dynamics. These findings highlight the importance of integrating ecological complexity and species-specific responses into vector surveillance and control strategies in rapidly urbanising African settings.

Anopheles funestus s.s. is a major human malaria vector across Africa. To study its evolution, especially under vector control pressure, we sequenced 656 modern specimens (collected 2014 to 2018) and 45 historic specimens (collected 1927 to 1967) from 16 African countries. Despite high genetic diversity, the species shows stable but considerable continental population structure. Although one population showed little differentiation over a century and 4000 kilometers, nearby, we found two genetically distinct ecotypes. Vector control has resulted in strong signals of selection, with some resistance alleles shared across populations through gene flow and others arising independently. Fortunately, we found that a promising gene drive target in Anopheles gambiae is highly conserved in An. funestus. These insights will enable more strategic insecticide usage and gene drive deployment, supporting malaria elimination.

The mosquito Aedes aegypti is the primary vector for dengue virus (DENV), which infects millions of people annually. Variability in DENV susceptibility among wild Ae. aegypti populations is governed by genetic factors, but specific causal variants are unknown. Here, we identify a cytochrome P450-encoding gene (CYP4G15) whose genetic variants drive differences in DENV susceptibility in a natural Ae. aegypti population. CYP4G15 is transiently upregulated in DENV-resistant midguts, while knockdown increases susceptibility, and transgenic overexpression enhances resistance. A naturally occurring 18-base-pair promoter deletion reduces CYP4G15 expression and confers higher DENV susceptibility. The unexpected role of a cytochrome P450 in DENV susceptibility challenges the long-standing focus on canonical immune pathways and opens new avenues for understanding antiviral defense and DENV transmission in mosquitoes.

AbstractThe mosquitoAedes aegyptiis the primary vector for dengue virus (DENV), which infects millions of people annually. Variability in DENV susceptibility among wildAe. aegyptipopulations is governed by genetic factors, but specific causal variants are unknown. Here, we identify a cytochrome P450-encoding gene (CYP4G15) whose variants drive differences in DENV susceptibility in a naturalAe. aegyptipopulation.CYP4G15is transiently upregulated in DENV-resistant midguts, while knockdown increases susceptibility, and transgenic overexpression enhances resistance. A naturally occurring 18-base-pair promoter deletion reducesCYP4G15expression and confers higher DENV susceptibility. The unexpected role of a cytochrome P450 in DENV susceptibility challenges the long-standing focus on canonical immune pathways and opens new avenues for understanding antiviral defense and DENV transmission in mosquitoes.

In December 2024, L’Initiative-Expertise France organized a workshop in Musanze, Rwanda, for National Malaria Control and Elimination Programmes (NMC/EPs) representatives from 19 sub-Saharan African countries. The workshop focused on surveillance, modeling, climate forecasting, and innovative control methods to mitigate climate change impacts on malaria. Participants shared challenges, experiences and best practices. Key challenges highlighted include shifts in malaria transmission seasons, disease spread to mid-altitude regions, and infrastructure damage from extreme weather. Additional factors, such as drug and insecticide resistance, the spread of Anopheles stephensi, and changes in vector behaviour, are exacerbating malaria transmission in African cities. Participants stressed the need for collaborative efforts to tackle these evolving threats. This comment reflects the expertise and insights of 19 NMCPs actively managing malaria control and aims at raising awareness, inform policy discussions, and strengthen global partnerships to address the intersection of malaria and climate change.

Understanding how life is adapting to urban environments represents an important challenge in evolutionary biology. In this work, we investigate a widely cited example of urban adaptation, Culex pipiens form molestus, also known as the London Underground mosquito. Population genomic analysis of ~350 contemporary and historical samples counters the popular hypothesis that molestus originated belowground in London <200 years ago. Instead, we show that molestus first adapted to human environments aboveground in the Mediterranean or Middle East over the course of more than 1000 years, possibly in association with ancient agricultural civilizations of the Middle East. Our results highlight the role of early human society in priming taxa for contemporary urban evolution. They also provide insight into whether and how molestus contributes to West Nile virus transmission in modern cities.

Plague is a rodent-borne disease transmitted to humans by the bite of fleas infected with the bacterium Yersinia pestis. Flea control is a key part of the overall plague management strategy. Insecticide-based strategies are designed to reduce or eliminate fleas from the environment in order to stop the disease transmission cycle during outbreaks. Many efforts have been directed toward monitoring flea susceptibility to insecticides using standardized bioassay methods recommended by the World Health Organization (WHO). Several studies have reported the development of insecticide resistance in vector species across Madagascar, which could be one of the factors contributing to the re-emergence of plague in endemic foci. However, the assessment of the operational efficacy of vector control in the field has received less attention. Furthermore, the mechanisms conferring flea resistance to insecticides remain poorly explored. In this review, we summarize the current understanding of (i) the effectiveness of insecticides for flea vector control in Madagascar, (ii) longitudinal surveillance of insecticide resistance in flea vector populations across the country, and (iii) insecticide resistance mechanisms in these fleas. Current vector control methods, including WHO standard methods for assessing the susceptibility or resistance of adult fleas, are presented and discussed. In addition, we propose recommendations for future research to improve the effectiveness of vector control and insecticide resistance mitigation for more effective control of plague-vector fleas in Madagascar.

Chromosomal inversions play a crucial role in evolution and have been found to regulate epidemiologically significant traits in malaria mosquitoes. However, they have not been characterized in Aedes aegypti, the primary vector of arboviruses, due to the poor structure of its polytene chromosomes. The Hi-C proximity ligation approach was used to identify chromosomal inversions in 25 strains of A. aegypti obtained from its worldwide distribution and in one strain of Aedes mascarensis. The study identified 21 multimegabase polymorphic inversions ranging in size from 5 to 55 Mbp. Inversions were more abundant in African than in non-African strains, 15 versus 3 inversions, with the highest number observed in West Africa. All inversions were grouped into two geographic clusters of African or non-African origin, suggesting their association with A. aegypti subspecies. Inversions were unevenly distributed along chromosomal arms, with the highest number found in the 1q and 3p arms homologous to the inversion-rich 2R chromosomal arm in the malaria vector Anopheles gambiae. Direct comparison of inversions between A. aegypti and An. gambiae revealed significant overlap in their genomic locations. This finding may explain the parallel evolution of the two species under similar environmental conditions. Some of the inversions colocalized with chemoreceptor genes and quantitative trait loci associated with pathogen infection, suggesting their potential role in host preference and disease transmission. Our study revealed the large pool of structural variations in the A. aegypti genome and provides the foundation for future studies of their impact on the biology of this important arboviral vector.

The yellow fever mosquito (Aedes aegypti) is an organism of high medical importance because it is the primary vector for diseases such as yellow fever, Zika, dengue, and chikungunya. Its medical importance has made it a subject of numerous efforts to understand their biology. One such effort, was the development of a high-quality reference genome (AaegL5). However, this reference genome was sourced from a highly inbred laboratory strain with unknown geographic origin. Thus, the reference is not representative of a wild mosquito, let alone one from its native range in sub-Saharan Africa. To better understand the genetic architecture of Ae. aegypti and their sister species, we developed two de novo chromosome-scale genomes with sequences sourced from single individuals: one of Ae. aegypti formosus (Aaf) from Burkina Faso and one of Ae. mascarensis (Am) from Mauritius. Both genomes exhibit high contiguity and gene completeness, comparable to AaegL5. While Aaf exhibits high degree of synteny to AaegL5, it also exhibits several large inversions. We also conducted comparative genomic analyses using our genomes and other publicly available culicid reference genomes to find extensive chromosomal rearrangements between major lineages. The expanded gene families common to Aaf, AaegL5, and Am revealed that while the overarching category of genes that have expanded are similar, the specific genes that have expanded differ. Our findings elucidate novel insights into chromosome evolution at both microevolutionary and macroevolutionary scales. The genomic resources we present are additions to a growing arsenal for biologists in understanding mosquito biology and genome evolution.

Laboratory study of natural populations of mosquitoes can play a key role in determining the underlying causes of variation in burdens of mosquito-borne disease. Aedes aegypti is the main vector of the viruses that cause dengue, chikungunya, Zika, and yellow fever, making it a high priority for laboratory study. Ae. aegypti eggs provide an ideal starting point for new laboratory colonies. Eggs can be collected using ovicups, which are small plastic cups lined with seed-germination paper and partially filled with leaf-infused H 2 O. Once collected, dry eggs will remain viable for months and can be safely transported long distances back to the laboratory as long as they are properly stored. This protocol provides step-by-step instructions for preparing for collecting, storing, and hatching Ae. aegypti eggs and has successfully yielded laboratory colonies from locations across both the native and invasive range of this species.

We present genome assembly from individual female An. coustani (African malaria mosquito; Arthropoda; Insecta; Diptera; Culicidae) from Lopé, Gabon. The genome sequence is 270 megabases in span. Most of the assembly is scaffolded into three chromosomal pseudomolecules with the X sex chromosome assembled for both species. The complete mitochondrial genome was also assembled and is 15.4 kilobases in length.

We present a genome assembly from an individual female Anopheles marshallii (the malaria mosquito; Arthropoda; Insecta; Diptera; Culicidae) from Lopé, Gabon. The genome sequence is 225.7 megabases in span. Most of the assembly is scaffolded into three chromosomal pseudomolecules with the X sex chromosome assembled. The complete mitochondrial genome was also assembled and is 15.4 kilobases in length.

Abstract The adaptation of Anopheles malaria vectors to domestic settings is directly linked to their ability to feed on humans. The strength of this species–habitat association is unequal across the species within the genus, with the major vectors being particularly dependent on humans. However, our understanding of how blood‐feeding behavior interacts with and adapts to environmental settings, including the presence of humans, remains limited. Using a field‐based approach, we first investigated Anopheles community structure and feeding behavior patterns in domestic and sylvatic settings in La Lopé National Park in Gabon, Central Africa. We characterized the preference indices using a dual‐host choice sampling approach across mosquito species, habitats, and seasons. We then quantified the plastic biting behavior of mosquito species in each habitat. We collected individuals from 16 Anopheles species that exhibited significant differences in species composition and abundance between sylvatic and domestic settings. The host‐seeking behavior also varied among the seven most abundant species. The general attractiveness to each host, human or animal, remained relatively constant for each species, but with significant variations between habitats across species. These variations, to more generalist and to more anthropophilic behavior, were related to seasonal changes and distance from the village, respectively. Finally, we pointed out that the host choice of major malaria vectors changed in the absence of humans, revealing a plastic feeding behavior of these species. This study highlights the effect of humans on Anopheles distribution and feeding evolution. The characterization of feeding behavior in wild and domestic settings provides opportunities to better understand the interplay between genetic determinants of host preference and ecological factors. Our findings suggest that protected areas may offer alternative thriving conditions to major malaria vectors.

Laboratory study of field-collected mosquitoes can allow researchers to better understand the ways variation within and among mosquito populations shapes burdens of mosquito-borne disease. The Anopheles gambiae complex comprises the most important vectors of malaria, but it can be challenging to keep in the laboratory. For some species of mosquitoes, especially An. gambiae , it is very difficult to bring viable eggs into the laboratory. Instead, it is preferable to collect larvae or pupae and then transport them as carefully as possible back to the laboratory. This simple protocol allows a researcher to start new laboratory colonies from larvae or pupae collected from natural breeding sites or proceed directly to their planned experiments. The use of natural breeding sites provides additional reassurance that the resulting colonies are representative of natural populations.

Chromosomal inversions play a fundamental role in evolution and have been shown to regulate epidemiologically important traits in malaria mosquitoes. However, they have never been characterized in Aedes aegypti, the major vector of arboviruses, because of the poor structure of its polytene chromosomes. In this study, we applied a Hi-C proximity ligation approach to identify chromosomal inversions in 25 strains of Ae. aegypti, acquired from its worldwide distribution, as well as in one strain of Ae. mascarensis. The study identified 21 multi-megabase inversions with uneven distributions along the three chromosomes. All chromosomal inversions, including one specific for Ae. mascarensis, were polymorphic. Nevertheless, geographic origin separated the strains into two clusters carrying African and non-African inversions suggesting their potential association with Ae. aegypti subspecies. Some of the inversions colocalized with chemoreceptor genes and quantitative trait loci associated with pathogen infection, implicating the potential role of inversions in host choice and disease transmission.