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The Democratic Republic of Congo (DRC) suffers from one of the highest malaria burdens worldwide, but information on its Anopheles vector populations is relatively limited. Preventative malaria control in DRC is reliant on pyrethroid-treated nets, raising concerns over the potential impacts of insecticide resistance. We sampled Anopheles gambiae from three geographically distinct populations (Kimpese, Kapolowe and Mikalayi) in southern DRC, collecting from three sub-sites per population and characterising mosquito collections from each for resistance to pyrethroids using WHO tube bioassays. Resistance to each of three different pyrethroids was generally high in An. gambiae with < 92% mortality in all tests, but varied between collections, with mosquitoes from Kimpese being the most resistant. Whole genome sequencing of 165 An. gambiae revealed evidence for genetic differentiation between Kimpese and Kapolowe/Mikalayi, but not between the latter two sample sites despite separation of approximately 800 km. Surprisingly, there was evidence of population structure at a small spatial scale between collection subsites in Kimpese, despite separation of just tens of kilometres. Intra-population (H12) and inter-population (F ST ) genome scans identified multiple peaks corresponding to genes associated with insecticide resistance such as the voltage gated sodium channel (Vgsc) target site on chromosome 2L, a Cyp6 cytochrome P450 cluster on chromosome arm 2R, and the Cyp9k1 P450 gene on chromosome X. In addition, in the Kimpese subsites, the P450 redox partner gene Cpr showed evidence for contemporary selection (H12) and population differentiation (F ST ) meriting further exploration as a potential resistance associated marker., (© 2024. Crown.)

Mitochondrial DNA has been a popular marker in phylogeography, phylogeny, and molecular ecology, but its complex evolution is increasingly recognized. Here, we investigated mitochondrial DNA variation in Anopheles gambiae and Anopheles coluzzii, in relation to other species in the Anopheles gambiae complex, by assembling the mitogenomes of 1,219 mosquitoes across Africa. The mitochondrial DNA phylogeny of the Anopheles gambiae complex was consistent with previously reported highly reticulated evolutionary history, revealing important discordances with the species tree. The three most widespread species (An. gambiae, An. coluzzii, and Anopheles arabiensis), known for extensive historical introgression, could not be discriminated based on mitogenomes. Furthermore, a monophyletic clustering of the three saltwater-tolerant species (Anopheles merus, Anopheles melas, and Anopheles bwambae) in the Anopheles gambiae complex also suggested that introgression and possibly selection shaped mitochondrial DNA evolution. Mitochondrial DNA variation in An. gambiae and An. coluzzii across Africa revealed significant partitioning among populations and species. A peculiar mitochondrial DNA lineage found predominantly in An. coluzzii and in the hybrid taxon of the African "far-west" exhibited divergence comparable to the interspecies divergence in the Anopheles gambiae complex, with a geographic distribution matching closely An. coluzzii's geographic range. This phylogeographic relict of the An. coluzzii and An. gambiae split was associated with population and species structure, but not with the rare Wolbachia occurrence. The lineage was significantly associated with single nucleotide polymorphisms in the nuclear genome, particularly in genes associated with pathogen and insecticide resistance. These findings underline potential mitonuclear coevolution history and the role played by mitochondria in shaping metabolic responses to pathogens and insecticides in Anopheles., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)

Background: Members of the Anopheles gambiae (s.l.) complex are one of the major vectors of malaria in Africa. LLINs and IRS are the most effective tools used in vector control of malaria. However, their effectiveness may be hampered by the development and spread of insecticide resistance in the target vectors species. The objective of this study was to assess the susceptibility of Anopheles gambiae (s.l.) mosquitoes from South-West Cameroon to deltamethrin, permethrin and to malathion, four years after the mass deployment of LLINs., Methods: Anopheles larvae were collected from Limbe, Tiko and Buea, three cities of the Fako division and reared until adult emergence. Adult mosquitoes from field larvae were identified as belonging to the Anopheles gambiae (s.l.) complex using standard identification keys. Susceptibility of mosquito samples to deltamethrin, permethrin and malathion was assessed using WHO susceptibility tests protocol for adult mosquitoes. Molecular identification of tested samples was performed using the PCR SINE200 protocol and by PCR-RFLP. The kdr alleles were genotyped using the hot ligation oligonucleotide assay (HOLA)., Results: Two species of the An. gambiae (s.l.) complex, An. coluzzii and An. gambiae (s.s.) were identified in all three study locations with high proportions of An. coluzzii in Limbe (84.06%) and Tiko (92.2%), while in Buea, An. coluzzii (55.6%) and An. gambiae (s.s.) (44.4%) occurred almost in the same proportions. Tested samples were found resistant to pyrethroids (deltamethrin and permethrin) in all locations (< 90% mortality), with > 3-fold increase of KDT 50 values compared with the Kisumu susceptible reference strain of An. gambiae (s.s.). However, the mosquito populations from Limbe and Buea were fully susceptible to malathion. The L1014F kdr was found in both An. coluzzii and An. gambiae (s.s.) with the highest frequencies found in An. gambiae (s.l.) populations from Tiko (94%) and Buea (90%) compared with the Limbe population (66%) (P = 0.00063, df = 2). No kdr L1014S was observed in analyzed samples., Conclusions: These findings reemphasize the ongoing development of An. gambiae (s.l.) resistance to pyrethroids used in impregnating LLINs and suggest the use of malathion as an alternative insecticide for IRS in complementarity with LLINs.

Mitochondrial DNA has been a popular marker in phylogeography, phylogeny, and molecular ecology, but its complex evolution is increasingly recognized. Here, we investigated mitochondrial DNA variation in Anopheles gambiae and Anopheles coluzzii , in relation to other species in the Anopheles gambiae complex, by assembling the mitogenomes of 1,219 mosquitoes across Africa. The mitochondrial DNA phylogeny of the Anopheles gambiae complex was consistent with previously reported highly reticulated evolutionary history, revealing important discordances with the species tree. The three most widespread species (An. gambiae, An. coluzzii , and Anopheles arabiensis), known for extensive historical introgression, could not be discriminated based on mitogenomes. Furthermore, a monophyletic clustering of the three saltwater-tolerant species (Anopheles merus , Anopheles melas , and Anopheles bwambae) in the Anopheles gambiae complex also suggested that introgression and possibly selection shaped mitochondrial DNA evolution. Mitochondrial DNA variation in An. gambiae and An. coluzzii across Africa revealed significant partitioning among populations and species. A peculiar mitochondrial DNA lineage found predominantly in An. coluzzii and in the hybrid taxon of the African " far-west " exhibited divergence comparable to the interspecies divergence in the Anopheles gambiae complex, with a geographic distribution matching closely An. coluzzii 's geographic range. This phylogeographic relict of the An. coluzzii and An. gambiae split was associated with population and species structure, but not with the rare Wolbachia occurrence. The lineage was significantly associated with single nucleotide polymorphisms in the nuclear genome, particularly in genes associated with pathogen and insecticide resistance. These findings underline potential mitonuclear coevolution history and the role played by mitochondria in shaping metabolic responses to pathogens and insecticides in Anopheles. [ABSTRACT FROM AUTHOR]

The molecular characterization of Anopheles gambiae complex mosquitoes in rice agroecosystems in Anambra State was studied from January to December 2020. The study was carried out in rice farms randomly selected from four local government areas in Anambra State. Mosquito larvae were collected with a WHO (350ml) standard dipper at the sampling point of each of the selected rice farms twice every month. The larval samples were taken to the insectary of the National Arbovirus and Vectors Research Centre (NAVRC) to be reared into adults. The molecular characterization of sibling species of Anopheles gambiae complex was accomplished with Polymerase Chain Reaction (PCR). A total of 289 An. gambiae complex mosquitoes were subjected to PCR and identified. The species were identified as An. gambiae s.s., 144 (49.8%) and An. coluzzii. 145 (50.1%). These observations indicated that malaria transmission in the Anambra state is mainly carried out by the Anopheles sibling species. This enhances, sustains, and extends the malaria disease transmission in this geographical area. [ABSTRACT FROM AUTHOR]

Background: Vector control is considered to be the most successful component of malaria prevention programs and a major contributor to the reduction of malaria incidence over the last two decades. However, the success of this strategy is threatened by the development of resistance to insecticides and behavioural adaptations of vectors. The aim of this study was to monitor malaria transmission and the distribution of insecticide resistance genes in Anopheles populations from three rural areas of the Moyen Ogooué Province of Gabon. Methods: Anopheles spp. were collected using human landing catches in Bindo, Nombakélé and Zilé, three villages located in the surroundings of Lambaréné, during both the rainy and dry seasons. Mosquitoes were identified morphologically, and DNA was extracted from heads and thoraces. Members of the Anopheles gambiae complex were identified by molecular methods using the PCR SINE200 protocol and by sequencing of the internal transcribed spacer 2 region. Taqman assays were used to determine Plasmodium infection and the presence of resistance alleles. Results: Anopheles gambiae sensu lato (97.7%), An. moucheti (1.7%) and An. coustani (0.6%) were the three groups of species collected. Anopheles gambiae sensu stricto (98.5%) and An. coluzzii (1.5%) were the only species of the An. gambiae complex present in the collection. Of the 1235 Anopheles collected, 1193 were collected during the rainy season; these exhibited an exophagic behaviour, and consistently more mosquitoes were collected outdoor than indoor in the three study areas. Of the 1166 Anopheles screened, 26 (2.2%) were infected with Plasmodium species, specifically Plasmodium falciparum (66.7%), P. malariae (15.4%), P. ovale curtisi (11.5%) and P. ovale wallikeri (3.8%). Malaria transmission intensity was high in Zilé, with an average annual entomological inoculation rate (aEIR) of 243 infective bites per year, while aEIRs in Bindo and Nombakélé were 80.2 and 17 infective bites per year, respectively. Both the L1014F and L1014S mutations were present at frequencies > 95% but no Ace1G119S mutation was found. Conclusion: Our results demonstrate that malaria transmission intensity is heterogeneous in these three rural areas of Moyen Ogooué Province, with areas of high transmission, such as Zilé. The exophagic behaviour of the mosquitoes as well as the high frequency of resistance mutations are serious challenges that need to be addressed by the deployment of control measures adapted to the local setting. [ABSTRACT FROM AUTHOR]

Background The SEMOS gold mine in Sadiola, southwestern Mali, has been implementing a malaria vector control programme for 15 y using indoor residual house spraying and sporadic larval control. Periodic screening of the vector populations have been carried out over the years to provide information to the control programme, mainly on vector species present and their insecticide resistance status. The data from five entomological surveys, carried out in 2006, 2011, 2014, 2016 and 2018, are presented. Methods Adult mosquitoes were collected resting on walls inside houses and on verandas. Insecticide susceptibility assays were carried out and mosquitoes subsequently identified by species using molecular assays. Results The major malaria vector mosquitoes, Anopheles gambiae and Anopheles arabiensis were abundant at each sampling period with Anopheles coluzzii and Anopheles funestus being rare or absent. Anopheles rivulorum was identified in 2006 and Anopheles leesoni in 2016. The presence of Anopheles rivulorum -like, identified for the first time in 2018, was not screened for in previous surveys. Insecticide susceptibility bioassays showed resistance in both A. gambiae and A. arabiensis to pyrethroids, carbamates and dichlorodiphenyltrichloroethane over the 12 y. Conclusions This is the first record of A. rivulorum -like west of Côte d'Ivoire. Resistance levels to the three classes of insecticides were variable but appeared to decrease after pyrethroids were discontinued for house spraying. [ABSTRACT FROM AUTHOR]

Background: Chromosomal inversion polymorphisms play a role in adaptation to heterogeneous environments. Inversion polymorphisms are implicated in the very high ecological flexibility of the three main malaria vector species of the Afrotropical Anopheles gambiae complex, facilitating the exploitation of anthropogenic environmental modifications and promoting a strong association with humans. In addition to extending the species' spatial and temporal distribution, inversions are associated with epidemiologically relevant mosquito behavior and physiology, underscoring their medical importance. We here present novel PCR-RFLP based assays strongly predictive of genotype for the cosmopolitan 2Rb inversion in An. coluzzii and An. gambiae, a development which overcomes the numerous constraints inherent to traditional cytological karyotyping. Methods: We designed PCR-RFLP genotyping assays based on tag SNPs previously computationally identified as strongly predictive (> 95%) of 2Rb genotype. We targeted those tags whose alternative allelic states destroyed or created the recognition site of a commercially available restriction enzyme, and designed assays with distinctive cleavage profiles for each inversion genotype. The assays were validated on 251 An. coluzzii and 451 An. gambiae cytologically karyotyped specimens from nine countries across Africa and one An. coluzzii laboratory colony. Results: For three tag SNPs, PCR-RFLP assays (denoted DraIII, MspAI, and TatI) reliably produced robust amplicons and clearly distinguishable electrophoretic profiles for all three inversion genotypes. Results obtained with the DraIII assay are ≥ 95% concordant with cytogenetic assignments in both species, while MspAI and TatI assays produce patterns highly concordant with cytogenetic assignments only in An. coluzzii or An. gambiae, respectively. Joint application of species-appropriate pairs of assays increased the concordance levels to > 99% in An. coluzzii and 98% in An. gambiae. Potential sources of discordance (e.g. imperfect association between tag and inversion, allelic dropout, additional polymorphisms in the restriction target site, incomplete or failed restriction digestion) are discussed. Conclusions: The availability of highly specific, cost effective and accessible molecular assays for genotyping 2Rb in An. gambiae and An. coluzzii allows karyotyping of both sexes and all developmental stages. These novel tools will accelerate deeper investigations into the role of this ecologically and epidemiologically important chromosomal inversion in vector biology. [ABSTRACT FROM AUTHOR]

Background: The SEMOS gold mine's malaria vector control programme forms part of the company's community responsibilities with the programme being managed by the mine's health department since 2005. Methods: Data from approximately 10 years of malaria vector control for the Sadiola District are given: namely malaria vector control methods used by the control programme, positive malaria case data and entomological surveys from 2006, 2011 and 2014. Results: Distribution of pyrethroid-treated bed nets and indoor residual spraying (IRS) with deltamethrin were implemented by the programme from 2005-2011. No IRS was done in 2012. Spraying with the organophosphate, pirimiphos-methyl resumed in 2013 and 2014 and was followed by a 70% drop in malaria cases in 2014. Anopheles arabiensis was the major vector present in 2006 and was susceptible to deltamethrin. In 2011 and 2014, An. gambiae s.s. was the most abundant vector with deltamethrin 24 h mortality of 68% and 19%, respectively. Conclusions: Resistance to the pyrethroid deltamethrin has increased in An. gambiae s.s. since 2011, possibly due to the scale-up in distribution of long-lasting insecticide-treated bed nets. Resistance management strategies are recommended using different classes of insecticides for IRS, and including the distribution of new-generation bed nets. [ABSTRACT FROM AUTHOR]

Malaria vector control targeting the larval stages of mosquitoes was applied successfully against many species of Anopheles (Diptera: Culicidae) in malarious countries until the mid-20th Century. Since the introduction of DDT in the 1940s and the associated development of indoor residual spraying (IRS), which usually has a more powerful impact than larval control on vectorial capacity, the focus of malaria prevention programmes has shifted to the control of adult vectors. In the Afrotropical Region, where malaria is transmitted mainly by Anopheles funestus Giles and members of the Anopheles gambiae Giles complex, gaps in information on larval ecology and the ability of An. gambiae sensu lato to exploit a wide variety of larval habitats have discouraged efforts to develop and implement larval control strategies. Opportunities to complement adulticiding with other components of integrated vector management, along with concerns about insecticide resistance, environmental impacts, rising costs of IRS and logistical constraints, have stimulated renewed interest in larval control of malaria vectors. Techniques include environmental management, involving the temporary or permanent removal of anopheline larval habitats, as well as larviciding with chemical or biological agents. This present review covers large-scale trials of anopheline larval control methods, focusing on field studies in Africa conducted within the past 15 years. Although such studies are limited in number and scope, their results suggest that targeting larvae, particularly in human-made habitats, can significantly reduce malaria transmission in appropriate settings. These approaches are especially suitable for urban areas, where larval habitats are limited, particularly when applied in conjunction with IRS and other adulticidal measures, such as the use of insecticide treated bednets. [ABSTRACT FROM AUTHOR]