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Macroinvertebrate predators such as backswimmers (Heteroptera: Notonectidae), dragonflies (Odonata: Aeshnidae), and predatory diving beetles (Coleoptera: Dytiscidae) naturally inhabit aquatic ecosystems. Some aquatic ecosystems inhabited by these macroinvertebrate predator taxa equally form malaria vector larval habitats. The presence of these predators in malaria vector larval habitats can negatively impact on development, adult body size, fecundity, and longevity of the malaria vectors, which form important determinants of their fitness and future vectorial capacity. These potential negative impacts caused by aquatic macroinvertebrate predators on malaria vectors warrant their consideration as biocontrol agents in an integrated program to combat malaria. However, the use of these macroinvertebrate predators in malaria biocontrol is currently constrained by technical bottlenecks linked to their generalist predatory tendencies and often long life cycles, demanding complex rearing systems. We reviewed the literature on the use of aquatic macroinvertebrate predators for biocontrol of malaria vectors from the An. gambiae s.l. complex. The available information from laboratory and semi-field studies has shown that aquatic macroinvertebrates have the potential to consume large numbers of mosquito larvae and could thus offer an additional approaches in integrated malaria vector management strategies. The growing number of semi-field structures available in East and West Africa provides an opportunity to conduct ecological experimental studies to reconsider the potential of using aquatic macroinvertebrate predators as a biocontrol tool. To achieve a more sustainable approach to controlling malaria vector populations, additional, non-chemical interventions could provide a more sustainable approach, in comparison with the failing chemical control tools, and should be urgently considered for integration with the current mosquito vector control campaigns. [ABSTRACT FROM AUTHOR]

Background The effect of clothing colour on the biting rates of different vector mosquito species is not well understood. Studies under tropical field conditions are lacking. This study aimed to determine the influence of clothing colours on mosquito biting rates in rural and suburban settings in West Africa. Methods We performed a simulated field study in a suburban and a rural site in Mali using Mosquito-Magnet traps utilizing CO2 and other attractants, which were covered with black, white, and black/white striped textile sheets covers. These targets operated continuously for 10 consecutive days with bright nights (around full moon) and 10 consecutive days with dark nights (around new moon). Trapped mosquitoes were collected and catch rates counted hourly. Mosquitoes were morphologically identified to the species complex level (Anopheles gambiae s.l. and Culex pipiens s.l.) or species level (Aedes aegypti). A subset of Anopheles specimens were further identified by molecular methods. Results Under bright-night conditions, An. gambiae s.l. was significantly more attracted to black targets than to white and striped targets; during dark nights, no target preference was noted. During bright nights, Cx. pipiens s.l. was significantly more attracted to black and striped targets than to white targets; a similar trend was noted during dark nights (not significant). For day-active Ae. aegypti , striped targets were more attractive than the other targets and black were more attractive than white targets. Conclusions The study firstly demonstrated that under field conditions in Mali, West Africa, mosquito catch rates were influenced by different clothing colours, depending on mosquito species and light conditions. Overall, light colours were least attractive to host-seeking mosquitoes. Using white or other light-coloured clothing can potentially reduce bite exposure and risk of disease transmission in endemic tropical regions. [ABSTRACT FROM AUTHOR]

Background: Malaria remains a major public health problem in sub-Saharan Africa, particularly in Benin. The present study aims to evaluate the different Plasmodium species transmitted by malaria vectors in the communes of Cove, Zagnanado and Ouinhi, Southern Benin. Methods: The study was conducted between December 2021 and October 2022 in 60 villages spread over the three study communes. Adult mosquitoes were collected from four houses in each village using human landing catches (HLCs). After morphological identification, a subsample of Anopheles gambiae, Anopheles funestus and Anopheles nili was analysed by PCR to test for their infection to the different Plasmodium species. Results: Anopheles gambiae was collected at higher frequency in all the three study communes, representing 93.5% (95% CI 92.9–94) of all collected mosquitoes (n = 10,465). In total, five molecular species were found, An. gambiae sensu stricto (s.s.) and Anopheles coluzzii of the Gambiae complex, An. funestus and Anopheles leesoni of the Funestus group, and An. nili s.s., the sole species of the Nili group. From the five molecular species, four (An. gambiae s.s., An. coluzzii, An. funestus s.s. and An. nili s.s.) were found to be infected. Plasmodium falciparum was the main Plasmodium species in the study area, followed by Plasmodium vivax and Plasmodium ovale. Only An. gambiae s.s. was infected with all three Plasmodium species, while An. coluzzii was infected with two species, P. falciparum and P. vivax. Conclusions: Plasmodium falciparum was the only species tested for in malaria vectors in Benin, and remains the only one against which most control tools are directed. It is, therefore, necessary that particular attention be paid to secondary Plasmodium species for an efficient control of the disease. The presence of P. vivax emphasizes the need for an update of case management for malaria. [ABSTRACT FROM AUTHOR]

Simple Summary: Malaria—a major cause of mortality in Africa—is transmitted to humans by Anopheles mosquitoes. The main approach to prevent bites and malaria transmission is to sleep under bed-nets impregnated by insecticides, which are largely available to the population. We collected mosquitoes either found indoors in the morning, or exiting the houses during the night, as well as information on the use of bed-nets in the sample houses, to help understanding the impact of these approach on mosquito biting and resting behavior. We confirmed high levels of malaria transmission in the two villages studied, despite a high use of bed-nets. A large proportion of Anopheles females exiting the houses during the night were not blood-fed, suggesting that bed-net use prevented them to find an available host indoors and led them to move outdoors to find one. However, a large proportion of females collected indoors were blood-fed, suggesting that prevention of bites was incomplete even when all people in a house declared to have slept under bed-net. Overall, results suggest a major role of bed-nets in protecting from mosquito bites and malaria transmission, but highlight that the level of protection is limited, likely due to mosquito and human behaviors. Malaria is still a leading cause mortality in Côte d'Ivoire despite extensive LLINs coverage. We present the results of an entomological survey conducted in a coastal and in an inland village with the aim to estimate Anopheles gambiae sensu lato (s.l.) female's abundance indoor/outdoor and Plasmodium falciparum infection rate and analyze the occurrence of blood-feeding in relation to LLINs use. Pyrethrum spray (PSC) and window exit traps (WT) collections were carried out to target endophagic/endophilic and endophagic/exophilic females, respectively. Data on LLINs use in sampled houses were collected. (1) high levels of malaria transmission despite LLINs coverage >70% (~1 An. gambiae s.l. predicted mean/person/night and ~5% Plasmodium falciparum infection rate); (2) 46% of females in the PSC sample were blood-fed, suggesting that they fed on an unprotected host inside the house; (3) 81% of females in WT were unfed, suggesting that they were leaving the house to find an available host. Model estimates that if everyone sleeps under LLINs the probability for a mosquito to bite decreases of 48% and 95% in the coastal and inland village, respectively. The results show a high proportion of mosquito biting and resting indoors despite extensive LLINs. The biological/epidemiological determinants of accounting for these results merit deeper investigations. [ABSTRACT FROM AUTHOR]

Antimalarial drugs that can block the transmission of Plasmodium gametocytes to mosquito vectors would be highly beneficial for malaria elimination efforts. Identifying transmission-blocking drugs currently relies on evaluation of their activity against gametocyte-producing laboratory parasite strains and would benefit from a testing pipeline with genetically diverse field isolates. The aims of this study were to develop a pipeline to test drugs against P. falciparum gametocyte field isolates and to evaluate the transmission-blocking activity of a set of novel compounds. Two assays were designed so they could identify both the overall transmission-blocking activity of a number of marketed and experimental drugs by direct membrane feeding assays (DMFA), and then also discriminate between those that are active against the gametocytes (gametocyte killing or sterilizing) or those that block development in the mosquito (sporontocidal). These DMFA assays used venous blood samples from naturally infected Plasmodium falciparum gametocyte carriers and locally reared Anopheles gambiae s.s. mosquitoes. Overall transmission-blocking activity was assessed following a 24 hour incubation of compound with gametocyte infected blood (TB-DMFA). Sporontocidal activity was evaluated following addition of compound directly prior to feeding, without incubation (SPORO-DMFA); Gametocyte viability was retained during 24-hour incubation at 37°C when gametocyte infected red blood cells were reconstituted in RPMI/serum. Methylene-blue, MMV693183, DDD107498, atovaquone and P218 showed potent transmission-blocking activity in the TB-DMFA, and both atovaquone and the novel antifolate P218 were potent inhibitors of sporogonic development in the SPORO-DMA. This work establishes a pipeline for the integral use of field isolates to assess the transmission-blocking capacity of antimalarial drugs to block transmission that should be validated in future studies. [ABSTRACT FROM AUTHOR]

The sibling species An. coluzzii and An. gambiae s.s. are major malaria vectors thought to be undergoing sympatric speciation with gene flow. In the absence of intrinsic post-zygotic isolation between the two taxa, speciation is thought possible through the association of assortative mating and genomic regions protected from gene flow by recombination suppression. Such genomic islands of speciation have been described in pericentromeric regions of the X, 2L and 3L chromosomes. Spatial swarm segregation plays a major role in assortative mating between sympatric populations of the two species and, given their importance for speciation, genes responsible for such pre-mating reproductive barriers are expected to be protected within divergence islands. In this study 2063 male and 266 female An. coluzzii and An. gambiae s.s. individuals from natural swarms in Burkina Faso, West Africa were sampled. These were genotyped at 16 speciation island SNPs, and characterized as non-hybrid individuals, F1 hybrids or recombinant F1+n backcrossed individuals. Their genotypes at each speciation island were associated with their participation in An. coluzzii and An. gambiae-like swarms. Despite extensive introgression between the two species, the X-island genotype of non-hybrid individuals (37.6%), F1 hybrids (0.1%) and F1+n recombinants (62.3%) of either sex perfectly associated to each swarm type. Associations between swarm type and the 3L and 2L speciation islands were weakened or broken down by introgression. The functional demonstration of a close association between spatial segregation behaviour and the X speciation island lends further support to sympatric speciation models facilitated by pericentric recombination suppression in this important species complex. [ABSTRACT FROM AUTHOR]

The sibling species An. coluzzii and An. gambiae s.s. are major malaria vectors thought to be undergoing sympatric speciation with gene flow. In the absence of intrinsic post-zygotic isolation between the two taxa, speciation is thought possible through the association of assortative mating and genomic regions protected from gene flow by recombination suppression. Such genomic islands of speciation have been described in pericentromeric regions of the X, 2L and 3L chromosomes. Spatial swarm segregation plays a major role in assortative mating between sympatric populations of the two species and, given their importance for speciation, genes responsible for such pre-mating reproductive barriers are expected to be protected within divergence islands. In this study 2063 male and 266 female An. coluzzii and An. gambiae s.s. individuals from natural swarms in Burkina Faso, West Africa were sampled. These were genotyped at 16 speciation island SNPs, and characterized as non-hybrid individuals, F1 hybrids or recombinant F1+n backcrossed individuals. Their genotypes at each speciation island were associated with their participation in An. coluzzii and An. gambiae-like swarms. Despite extensive introgression between the two species, the X-island genotype of non-hybrid individuals (37.6%), F1 hybrids (0.1%) and F1+n recombinants (62.3%) of either sex perfectly associated to each swarm type. Associations between swarm type and the 3L and 2L speciation islands were weakened or broken down by introgression. The functional demonstration of a close association between spatial segregation behaviour and the X speciation island lends further support to sympatric speciation models facilitated by pericentric recombination suppression in this important species complex. [ABSTRACT FROM AUTHOR]

Background: Pyrethroid-PBO nets were conditionally recommended for control of malaria transmitted by mosquitoes with oxidase-based pyrethroid-resistance based on epidemiological evidence of additional protective effect with Olyset Plus compared to a pyrethroid-only net (Olyset Net). Entomological studies can be used to assess the comparative performance of other brands of pyrethroid-PBO ITNs to Olyset Plus. Methods: An experimental hut trial was performed in Cové, Benin to compare PermaNet 3.0 (deltamethrin plus PBO on roof panel only) to Olyset Plus (permethrin plus PBO on all panels) against wild pyrethroid-resistant Anopheles gambiae sensu lato (s.l.) following World Health Organization (WHO) guidelines. Both nets were tested unwashed and after 20 standardized washes compared to Olyset Net. Laboratory bioassays were also performed to help explain findings in the experimental huts. Results: With unwashed nets, mosquito mortality was higher in huts with PermaNet 3.0 compared to Olyset Plus (41% vs. 28%, P < 0.001). After 20 washes, mortality declined significantly with PermaNet 3.0 (41% unwashed vs. 17% after washing P < 0.001), but not with Olyset Plus (28% unwashed vs. 24% after washing P = 0.433); Olyset Plus induced significantly higher mortality than PermaNet 3.0 and Olyset Net after 20 washes. PermaNet 3.0 showed a higher wash retention of PBO compared to Olyset Plus. A non-inferiority analysis performed with data from unwashed and washed nets together using a margin recommended by the WHO, showed that PermaNet 3.0 was non-inferior to Olyset Plus in terms of mosquito mortality (25% with Olyset Plus vs. 27% with PermaNet 3.0, OR = 1.528, 95%CI = 1.02–2.29) but not in reducing mosquito feeding (25% with Olyset Plus vs. 30% with PermaNet 3.0, OR = 1.192, 95%CI = 0.77–1.84). Both pyrethroid-PBO nets were superior to Olyset Net. Conclusion: Olyset Plus outperformed PermaNet 3.0 in terms of its ability to cause greater margins of improved mosquito mortality compared to a standard pyrethroid net, after multiple standardized washes. However, using a margin of non-inferiority defined by the WHO, PermaNet 3.0 was non-inferior to Olyset Plus in inducing mosquito mortality. Considering the low levels of mortality observed and increasing pyrethroid-resistance in West Africa, it is unclear whether either of these nets would demonstrate the same epidemiological impact observed in community trials in East Africa. [ABSTRACT FROM AUTHOR]

Agricultural production activities usually occur in Benin with the use of a huge amount of insecticides including pyrethroids for pest control. It is therefore important to regularly monitor pyrethroid resistance intensity in Anopheles gambiae s.l., the main malaria vector. This study was conducted in cereal, cotton, rice growing, and urban market gardening areas throughout the country in 2018 and 2019. Females An. gambiae s.l. field-collected as larvae were exposed to deltamethrin 1 × (0.05%), 2 × (0.1%), 5 × (0.25%), and 10 × (0.5%) and permethrin 1 × (0.75%), 2 × (1.5%), 5 × (3.75%), and 10 × (7.5%). Synergist assays were also performed using World Health Organization articles combining piperonyl butoxide (PBO) (4%) + deltamethrin 1 × and, PBO (4%) + Permethrin 1 × . Molecular species and L1014F kdr mutation were identified using PCR. Expression of metabolic enzymes was also assessed through biochemical tests. After exposure to permethrin and deltamethrin 10 × , An. gambiae s.l. displayed mortality rates <98%. Synergist assays induced significantly higher mortality rates than pyrethroids alone (p < 0.05). An. gambiae s.l. complex was composed of An. gambiae s.s., Anopheles coluzzii, and Anopheles arabiensis, with mean frequency of the L1014F kdr mutation >75%. Overexpression of nonspecific α and β esterases was observed in the cereal, cotton, and urban market gardening areas, while an overexpression of mixed function oxidases was observed in the cotton and rice growing areas. Overall, An. gambiae s.l. showed high resistance intensity to both deltamethrin and permethrin. The synergist and biochemical tests performed suggest that PBO long-lasting insecticidal nets may provide a greater control of pyrethroid-resistant mosquitoes. [ABSTRACT FROM AUTHOR]

The Institut de Recherche en Sciences de la Santé (IRSS) of Burkina Faso, West Africa, was the first African institution to import transgenic mosquitoes for research purposes. A shift from the culture of mosquito research to regulated biotechnology research and considerable management capacity is needed to set up and run the first insectary for transgenic insects in a country that applied and adapted the existing biosafety framework, first developed for genetically modified (GM) crops, to this new area of research. The additional demands arise from the separate regulatory framework for biotechnology, referencing the Cartagena Protocol on Biosafety, and the novelty of the research strain, making public understanding and acceptance early in the research pathway important. The IRSS team carried out extensive preparations following recommendations for containment of GM arthropods and invested efforts in local community engagement and training with scientific colleagues throughout the region. Record keeping beyond routine practice was established to maintain evidence related to regulatory requirements and risk assumptions. The National Biosafety Agency of Burkina Faso, Agence Nationale de Biosécurité (ANB), granted the permits for import of the self-limiting transgenic mosquito strain, which took place in November 2016, and for conducting studies in the IRSS facility in Bobo-Dioulasso. Compliance with permit terms and conditions of the permits and study protocols continued until the conclusion of studies, when the transgenic colonies were terminated. All this required close coordination between management and the insectary teams, as well as others. This article outlines the experiences of the IRSS to support others undertaking such studies. The IRSS is contributing to the ongoing development of genetic technologies for malaria control, as a partner of Target Malaria. The ultimate objective of the innovation is to reduce malaria transmission by using GM mosquitoes of the same species released to reduce the disease-vectoring native populations of Anopheles gambiae s.l. [ABSTRACT FROM AUTHOR]

Background: Existing mechanisms of insecticide resistance are known to help the survival of mosquitoes following contact with chemical compounds, even though they could negatively affect the life-history traits of resistant malaria vectors. In West Africa, the knockdown resistance mechanism kdrR (L1014F) is the most common. However, little knowledge is available on its effects on mosquito life-history traits. The fitness effects associated with this knockdown resistance allele in Anopheles gambiae sensu stricto (s.s.) were investigated in an insecticide-free laboratory environment. Methods: The life-history traits of Kisumu (susceptible) and KisKdr (kdr resistant) strains of An. gambiae s.s. were compared. Larval survivorship and pupation rate were assessed as well as fecundity and fertility of adult females. Female mosquitoes of both strains were directly blood fed through artificial membrane assays and then the blood-feeding success, blood volume and adult survivorship post-blood meal were assessed. Results: The An. gambiae mosquitoes carrying the kdrR allele (KisKdr) laid a reduced number of eggs. The mean number of larvae in the susceptible strain Kisumu was three-fold overall higher than that seen in the KisKdr strain with a significant difference in hatching rates (81.89% in Kisumu vs 72.89% in KisKdr). The KisKdr larvae had a significant higher survivorship than that of Kisumu. The blood-feeding success was significantly higher in the resistant mosquitoes (84%) compared to the susceptible ones (34.75%). However, the mean blood volume was 1.36 µL/mg, 1.45 µL/mg and 1.68 µL/mg in Kisumu, homozygote and heterozygote KisKdr mosquitoes, respectively. After blood-feeding, the heterozygote KisKdr mosquitoes displayed highest survivorship when compared to that of Kisumu. Conclusions: The presence of the knockdown resistance allele appears to impact the life-history traits, such as fecundity, fertility, larval survivorship, and blood-feeding behaviour in An. gambiae. These data could help to guide the implementation of more reliable strategies for the control of malaria vectors. [ABSTRACT FROM AUTHOR]

Background: Due to the lack of vaccines, malaria control mainly involves the control of anopheline vectors (Anopheles spp.) using chemical insecticides. However, the prolonged and indiscriminate use of these compounds has led to the emergence of resistance in Anopheles populations in Africa. Insecticide resistance surveillance programs are less frequent in Cabo Verde than in other African countries. This study aimed to investigate the circulation of the L1014F and L1014S alleles in natural populations of Anopheles arabiensis collected from two sampling sites in the city of Praia, Cabo Verde. Methods: Anopheles larvae were collected from the two sampling sites and reared in the laboratory until the adult stage. Mosquitoes were first morphologically identified by classical taxonomy and then by molecular species identification using molecular markers. All Anopheles arabiensis were subjected to PCR analysis to screen for mutations associated to resistance in the Nav gene. Results: A total of 105 mosquitoes, all belonging to the Anopheles gambiae complex, were identified by classical taxonomy as well as by molecular taxonomy. Molecular identification showed that 100% of the An. gambiae senso lato specimens analyzed corresponded to An. arabiensis. Analysis of the Nav gene revealed the presence of L1014S and L1014F alleles with frequencies of 0.10 and 0.19, respectively. Conclusions: Our data demonstrated, for the first time, the presence of the L1014F allele in the An. arabiensis population from Cabo Verde, as well as an increase in the frequency of the kdr L1014S allele reported in a previous study. The results of this study demonstrate the need to establish new approaches in vector control programs in Cabo Verde. [ABSTRACT FROM AUTHOR]

Background: Since the late 1990s, malaria control programmes have relied extensively on mass bednet distribution and indoor residual spraying. Both interventions use pesticides and target mosquitoes coming indoors either to feed or to rest. Unfortunately, these intensified vector control campaigns have resulted in mosquito populations with high levels of resistance to most of the chemical compounds used against them and which are increasingly exophagic and exophillic, hence difficult to monitor indoors. Consequently, there is an urgent need for novel tools to sample outdoor anopheline populations for monitoring interventions and disease surveillance programmes. Methodologies: In this study, we tested several modifications and configurations of the BioGents® Sentinel (BGS) trap, designed with the aim to increase its efficacy for sampling malaria vector species. Traps were used with chemical attractants and CO2, and the impacts of trap position, trap colour contrast combination and the addition of a heat source were tested in two studies conducted in the Sudano-Sahelian region of Burkina Faso and Mali. Results: The results show that of all the configurations tested, the addition of a heat source to the BGS trap with the original colour combination and an upward positioning resulted in a 1.8- and 5.9-fold increase in host-seeking Anopheles gambiae (s.l.) females in the experiments performed in Burkina Faso and Mali, respectively. BGS with heat traps, referred to as BGSH traps, captured An. gambiae (s.l.), An. pharoensis, An. coustani, Culex and Mansonia spp. Importantly, the results suggest that their efficacy does not depend on the close proximity of nearby hosts in houses. Conclusions: The results suggest that BGSH traps can be an effective scalable tool for sampling outdoor anopheline vector populations. Further developments enabling CO2 and heat generation for longer periods of time would further improve the trap's versatility for large-scale surveillance programmes. [ABSTRACT FROM AUTHOR]

Background: Insecticide-based vector control is responsible for reducing malaria mortality and morbidity. Its success depends on a better knowledge of the vector, its distribution, and resistance status to the insecticides used. In this paper, we assessed Anopheles gambiae sensu lato (A gambiae s.l.) population resistance to pyrethroids in different ecological settings.Methods: The World Health Organization standard bioassay test was used to assess F0A gambiae s.l. susceptibility to pyrethroids. Biochemical Synergist assays were conducted with piperonyl butoxide (PBO), S,S,S-tributyl phosphotritioate, and diethyl maleate. L1014F, L1014S, and N1575Y knockdown resistance (kdr) mutations were investigated using TaqMan genotyping.Results: Anopheles gambiae sensu lato was composed of Anopheles arabienisis, Anopheles coluzzii, and A gambiae in all study sites. Anopheles gambiae sensu lato showed a strong phenotypic resistance to deltamethrin and permethrin in all sites (13% to 41% mortality). In many sites, pre-exposure to synergists partially improved the mortality rate suggesting the presence of detoxifying enzymes. The 3 kdr (L1014F, L1014S, and N1575Y) mutations were found, with a predominance of L1014F, in all species.Conclusions: Multiple resistance mechanisms to pyrethroids were observed in A gambiae s.l. in Mali. The PBO provided a better partial restoration of susceptibility to pyrethroids, suggesting that the efficacy of long-lasting insecticidal nets may be improved with PBO. [ABSTRACT FROM AUTHOR]

Background: Population suppression gene drive has been proposed as a strategy for malaria vector control. A CRISPR-Cas9-based transgene homing at the doublesex locus (dsxFCRISPRh) has recently been shown to increase rapidly in frequency in, and suppress, caged laboratory populations of the malaria mosquito vector Anopheles gambiae. Here, problem formulation, an initial step in environmental risk assessment (ERA), was performed for simulated field releases of the dsxFCRISPRh transgene in West Africa. Methods: Building on consultative workshops in Africa that previously identified relevant environmental and health protection goals for ERA of gene drive in malaria vector control, 8 potentially harmful effects from these simulated releases were identified. These were stratified into 46 plausible pathways describing the causal chain of events that would be required for potential harms to occur. Risk hypotheses to interrogate critical steps in each pathway, and an analysis plan involving experiments, modelling and literature review to test each of those risk hypotheses, were developed. Results: Most potential harms involved increased human (n = 13) or animal (n = 13) disease transmission, emphasizing the importance to subsequent stages of ERA of data on vectorial capacity comparing transgenics to non-transgenics. Although some of the pathways (n = 14) were based on known anatomical alterations in dsxFCRISPRh homozygotes, many could also be applicable to field releases of a range of other transgenic strains of mosquito (n = 18). In addition to population suppression of target organisms being an accepted outcome for existing vector control programmes, these investigations also revealed that the efficacy of population suppression caused by the dsxFCRISPRh transgene should itself directly affect most pathways (n = 35). Conclusions: Modelling will play an essential role in subsequent stages of ERA by clarifying the dynamics of this relationship between population suppression and reduction in exposure to specific potential harms. This analysis represents a comprehensive identification of plausible pathways to potential harm using problem formulation for a specific gene drive transgene and organism, and a transparent communication tool that could inform future regulatory studies, guide subsequent stages of ERA, and stimulate further, broader engagement on the use of population suppression gene drive to control malaria vectors in West Africa. [ABSTRACT FROM AUTHOR]

In West Africa, the Anopheles gambiae sensu lato (s.l.) complex mosquitoes are the main malaria vectors. Malaria control relies mainly on long-lasting insecticide-treated nets (LLINs) and to a lesser extent on indoor residual spray (IRS) of insecticides. Important progress has been made in terms of malaria morbidity and mortality in these past decades. Resistance to insecticides in An. gambiae s.l. was first attributed to their use in agriculture. Further, their use in public health increased selection pressure. Resistance has been recorded to the four main classes of insecticides used in public health in West Africa. However, the spread of insecticide resistance in West Africa is persistent due to the lack of management of resistance monitoring. Resistance to insecticides involves different mechanisms. Resistance to pyrethroids and organochlorines was caused by target modification such as some sodium channel mutations in addition to metabolic changes. Reduction of sensitivity to organophosphates and carbamates was caused by acetylcholinesterase mutations. Therefore, efforts should be made as quickly as possible to develop novel vector control techniques. Furthermore, it is also suggested to combine environmental, chemical, and biological management. In this review, we outline the insecticide resistance of Anopheles in West Africa and the current alternative tools for effective mosquito vector control. [ABSTRACT FROM AUTHOR]

Background: Since the late 1990s, malaria control programmes have relied extensively on mass bednet distribution and indoor residual spraying. Both interventions use pesticides and target mosquitoes coming indoors either to feed or to rest. Unfortunately, these intensified vector control campaigns have resulted in mosquito populations with high levels of resistance to most of the chemical compounds used against them and which are increasingly exophagic and exophillic, hence difficult to monitor indoors. Consequently, there is an urgent need for novel tools to sample outdoor anopheline populations for monitoring interventions and disease surveillance programmes. Methodologies: In this study, we tested several modifications and configurations of the BioGents® Sentinel (BGS) trap, designed with the aim to increase its efficacy for sampling malaria vector species. Traps were used with chemical attractants and CO2, and the impacts of trap position, trap colour contrast combination and the addition of a heat source were tested in two studies conducted in the Sudano-Sahelian region of Burkina Faso and Mali. Results: The results show that of all the configurations tested, the addition of a heat source to the BGS trap with the original colour combination and an upward positioning resulted in a 1.8- and 5.9-fold increase in host-seeking Anopheles gambiae (s.l.) females in the experiments performed in Burkina Faso and Mali, respectively. BGS with heat traps, referred to as BGSH traps, captured An. gambiae (s.l.), An. pharoensis, An. coustani, Culex and Mansonia spp. Importantly, the results suggest that their efficacy does not depend on the close proximity of nearby hosts in houses. Conclusions: The results suggest that BGSH traps can be an effective scalable tool for sampling outdoor anopheline vector populations. Further developments enabling CO2 and heat generation for longer periods of time would further improve the trap's versatility for large-scale surveillance programmes. [ABSTRACT FROM AUTHOR]

Background: Since the late 1990s, malaria control programmes have relied extensively on mass bednet distribution and indoor residual spraying. Both interventions use pesticides and target mosquitoes coming indoors either to feed or to rest. Unfortunately, these intensified vector control campaigns have resulted in mosquito populations with high levels of resistance to most of the chemical compounds used against them and which are increasingly exophagic and exophillic, hence difficult to monitor indoors. Consequently, there is an urgent need for novel tools to sample outdoor anopheline populations for monitoring interventions and disease surveillance programmes. Methodologies: In this study, we tested several modifications and configurations of the BioGents® Sentinel (BGS) trap, designed with the aim to increase its efficacy for sampling malaria vector species. Traps were used with chemical attractants and CO2, and the impacts of trap position, trap colour contrast combination and the addition of a heat source were tested in two studies conducted in the Sudano-Sahelian region of Burkina Faso and Mali. Results: The results show that of all the configurations tested, the addition of a heat source to the BGS trap with the original colour combination and an upward positioning resulted in a 1.8- and 5.9-fold increase in host-seeking Anopheles gambiae (s.l.) females in the experiments performed in Burkina Faso and Mali, respectively. BGS with heat traps, referred to as BGSH traps, captured An. gambiae (s.l.), An. pharoensis, An. coustani, Culex and Mansonia spp. Importantly, the results suggest that their efficacy does not depend on the close proximity of nearby hosts in houses. Conclusions: The results suggest that BGSH traps can be an effective scalable tool for sampling outdoor anopheline vector populations. Further developments enabling CO2 and heat generation for longer periods of time would further improve the trap's versatility for large-scale surveillance programmes. [ABSTRACT FROM AUTHOR]

Background: The sibling species of the malaria mosquito, Anopheles gambiae (sensu stricto) and Anopheles coluzzii co-exist in many parts of West Africa and are thought to have recently diverged through a process of ecological speciation with gene flow. Divergent larval ecological adaptations, resulting in Genotype-by-Environment (G × E) interactions, have been proposed as important drivers of speciation in these species. In West Africa, An. coluzzii tends to be associated with permanent man-made larval habitats such as irrigated rice fields, which are typically more eutrophic and mineral and ammonia-rich than the temporary rain pools exploited by An. gambiae (s.s.) Methods: To highlight G × E interactions at the larval stage and their possible role in ecological speciation of these species, we first investigated the effect of exposure to ammonium hydroxide and water mineralisation on larval developmental success. Mosquito larvae were exposed to two water sources and increasing ammonia concentrations in small containers until adult emergence. In a second experiment, larval developmental success was compared across two contrasted microcosms to highlight G × E interactions under conditions such as those found in the natural environment. Results: The first experiment revealed significant G × E interactions in developmental success and phenotypic quality for both species in response to increasing ammonia concentrations and water mineralisation. The An. coluzzii strain outperformed the An. gambiae (s.s.) strain under limited conditions that were closer to more eutrophic habitats. The second experiment revealed divergent crisscrossing reaction norms in the developmental success of the sibling species in the two contrasted larval environments. As expected, An. coluzzii had higher emergence rates in the rice paddy environment with emerging adults of superior phenotypic quality compared to An. gambiae (s.s.), and vice versa, in the rain puddle environment. Conclusions: Evidence for such G × E interactions lends support to the hypothesis that divergent larval adaptations to the environmental conditions found in man-made habitats such as rice fields in An. coluzzii may have been an important driver of its ecological speciation. [ABSTRACT FROM AUTHOR]

Chromosomal inversion polymorphisms have special importance in the Anopheles gambiae complex of malaria vector mosquitoes, due to their role in local adaptation and range expansion. The study of inversions in natural populations is reliant on polytene chromosome analysis by expert cytogeneticists, a process that is limited by the rarity of trained specialists, low throughput, and restrictive sampling requirements. To overcome this barrier, we ascertained tag single nucleotide polymorphisms (SNPs) that are highly correlated with inversion status (inverted or standard orientation). We compared the performance of the tag SNPs using two alternative high throughput molecular genotyping approaches versus traditional cytogenetic karyotyping of the same 960 individual An. gambiae and An. coluzzii mosquitoes sampled from Burkina Faso, West Africa. We show that both molecular approaches yield comparable results, and that either one performs as well or better than cytogenetics in terms of genotyping accuracy. Given the ability of molecular genotyping approaches to be conducted at scale and at relatively low cost without restriction on mosquito sex or developmental stage, molecular genotyping via tag SNPs has the potential to revitalize research into the role of chromosomal inversions in the behavior and ongoing adaptation of An. gambiae and An. coluzzii to environmental heterogeneities. [ABSTRACT FROM AUTHOR]

Background: Malaria is a major public health problem and life threatening parasitic vector-borne disease. For the first time, we established and report the molecular mechanism responsible for Anopheles gambiaes.l. resistance to pyrethroids and DDT from Yamaltu Deba, Southern Guinea Savanna, Northern-Nigeria. Methods: The susceptibility profile of An. gambiaes.l. to four insecticides (DDT 4%, bendiocarb 0.1%, malathion 5% and deltamethrin 0.05%) using 2–3 days old females from larvae collected from study area between August and November, 2018 was first established. Genomic DNA was then extracted from 318 mosquitoes using Livak DNA extraction protocol for specie identification and kdr genotyping. The mosquitoes were identified to species level and then 96 genotyped for L1014F and L1014S kdr target site mutations. Results: The mosquitoes were all resistant to DDT, bendiocarb and deltamethrin but fully susceptible to malathion. An. coluzzii was found to be the dominant sibling species (97.8%) followed by An. arabiensis(1.9%) and An. gambiae s.s(0.3%). The frequency of the L1014F kdr mutation was relatively higher (83.3%) than the L1014S (39%) in the three species studied. The L1014F showed a genotypic frequency of 75% resistance (RR), 17% heterozygous (RS) and 8% susceptible (SS) with an allelic frequency of 87% RR and 13% SSwhile the L1014S showed a genotypic frequency of RR (16%), RS (38%) and SS (46%) with an allelic frequency of 40% RR and 60% SS, respectively. Conclusion: This study reveals that both kdr mutations present simultaneously in Northern-Nigeria, however contribution of L1014F which is common in West Africa was more than twice of L1014S mutation found in East Africa. [ABSTRACT FROM AUTHOR]

Background: Despite the overall major impact of long-lasting insecticide treated nets (LLINs) in eliciting individual and collective protection to malaria infections, some sub-Saharan countries, including Burkina Faso, still carry a disproportionately high share of the global malaria burden. This study aims to analyse the possible entomological bases of LLIN limited impact, focusing on a LLIN-protected village in the Plateau Central region of Burkina Faso. Methods: Human landing catches (HLCs) were carried out in 2015 for 12 nights both indoors and outdoors at different time windows during the highest biting activity phase for Anopheles gambiae (s.l.). Collected specimens were morphologically and molecularly identified and processed for Plasmodium detection and L1014F insecticide-resistance allele genotyping. Results: Almost 2000 unfed An. gambiae (s.l.) (54% Anopheles coluzzii and 44% Anopheles arabiensis) females landing on human volunteers were collected, corresponding to a median number of 23.5 females/person/hour. No significant differences were observed in median numbers of mosquitoes collected indoors and outdoors, nor between sporozoite rates in An. coluzzii (6.1%) and An. arabiensis (5.5%). The estimated median hourly entomological inoculation rate (EIR) on volunteers was 1.4 infective bites/person/hour. Results do not show evidence of the biting peak during night hours typical for An. gambiae (s.l.) in the absence of bednet protection. The frequency of the L1014F resistant allele (n = 285) was 66% in An. coluzzii and 38% in An. arabiensis. Conclusions: The observed biting rate and sporozoite rates are in line with the literature data available for An. gambiae (s.l.) in the same geographical area before LLIN implementation and highlight high levels of malaria transmission in the study village. Homogeneous biting rate throughout the night and lack of preference for indoor-biting activity, suggest the capacity of both An. coluzzii and An. arabiensis to adjust their host-seeking behaviour to bite humans despite bednet protection, accounting for the maintenance of high rates of mosquito infectivity and malaria transmission. These results, despite being limited to a local situation in Burkina Faso, represent a paradigmatic example of how high densities and behavioural plasticity in the vector populations may contribute to explaining the limited impact of LLINs on malaria transmission in holo-endemic Sudanese savannah areas in West Africa. [ABSTRACT FROM AUTHOR]

Background: The aim of this field trial was to evaluate the efficacy of attractive toxic sugar baits (ATSB) in Mali, where sustained malaria transmission occurs despite the use of long-lasting insecticidal nets (LLINs). ATSB bait stations were deployed in seven of 14 similar study villages, where LLINs were already in widespread use. The combined use of ATSB and LLINs was tested to see if it would substantially reduce parasite transmission by Anopheles gambiae sensu lato beyond use of LLINs alone. Methods: A 2-day field experiment was conducted to determine the number of mosquitoes feeding on natural sugar versus those feeding on bait stations containing attractive sugar bait without toxin (ASB)—but with food dye. This was done each month in seven random villages from April to December 2016. In the following year, in seven treatment villages from May to December 2017, two ATSB bait stations containing the insecticide dinotefuran were placed on the outer walls of each building. Vector population density was evaluated monthly by CDC UV light traps, malaise traps, pyrethrum spray (PSCs) and human landing catches (HLCs). Female samples of the catch were tested for age by examination of the ovarioles in dissected ovaries and identification of Plasmodium falciparum sporozoite infection by ELISA. Entomological inoculation rates (EIR) were calculated, and reductions between treated and untreated villages were determined. Results: In the 2-day experiment with ASB each month, there was a lower number of male and female mosquitoes feeding on the natural sugar sources than on the ASB. ATSB deployment reduced CDC-UV trap female catches in September, when catches were highest, were by 57.4% compared to catches in control sites. Similarly, malaise trap catches showed a 44.3% reduction of females in August and PSC catches of females were reduced by 48.7% in September. Reductions of females in HLCs were lower by 19.8% indoors and 26.3% outdoors in September. The high reduction seen in the rainy season was similar for males and reductions in population density for both males and females were > 70% during the dry season. Reductions of females with ≥ 3 gonotrophic cycles were recorded every month amounting to 97.1% in October and 100.0% in December. Reductions in monthly EIRs ranged from 77.76 to 100.00% indoors and 84.95% to 100.00% outdoors. The number of sporozoite infected females from traps was reduced by 97.83% at treated villages compared to controls. Conclusions: Attractive toxic sugar baits used against Anopheles mosquitoes in Mali drastically reduced the density of mosquitoes, the number of older females, the number of sporozoite infected females and the EIR demonstrating how ATSB significantly reduces malaria parasite transmission. [ABSTRACT FROM AUTHOR]

Background: Bubaque is the most populous island of the Bijagos archipelago, a group of malaria-endemic islands situated off the coast of Guinea-Bissau, West Africa. Malaria vector control on Bubaque relies almost exclusively on the use of long-lasting insecticidal nets (LLINs). However, there is little information on local vector bionomics and insecticide resistance. Methods: A survey of mosquito species composition was performed at the onset of the wet season (June/July) and the beginning of the dry season (November/December). Sampling was performed using indoor adult light-traps and larval dipping. Anopheles mosquitoes were identified to species level and assessed for kdr allele frequency by TaqMan PCR. Females were analysed for sporozoite positivity by CSP-ELISA. Resistance to permethrin and α-cypermethrin was measured using the CDC-bottle bioassay incorporating the synergist piperonyl-butoxide. Results: Several Anopheles species were found on the island, all belonging to the Anopheles gambiae sensu lato (s.l.) complex, including An. gambiae sensu stricto, Anopheles coluzzii, Anopheles melas, and An. gambiae/An. coluzzii hybrids. Endophagic Anopheles species composition and abundance showed strong seasonal variation, with a majority of An. gambiae (50% of adults collected) caught in June/July, while An. melas was dominant in November/December (83.9% of adults collected). Anopheles gambiae had the highest sporozoite rate in both seasons, with infection rates of 13.9% and 20% in June/July and November/December, respectively. Moderate frequencies of the West African kdr allele were found in An. gambiae (36%), An. coluzzii (35%), An. gambiae/An. coluzzii hybrids (42%). Bioassays suggest moderate resistance to α-cypermethrin, but full susceptibility to permethrin. Conclusions: The island of Bubaque maintained an An. gambiae s.l. population in both June/July and November/December. Anopheles gambiae was the primary vector at the onset of the wet season, while An. melas is likely to be responsible for most dry season transmission. There was moderate kdr allele frequency and synergist assays suggest likely metabolic resistance, which could reduce the efficacy of LLINs. Future control of malaria on the islands should consider the seasonal shift in mosquito species, and should employ continuous monitoring for insecticide resistance. [ABSTRACT FROM AUTHOR]

Background: The fight against malaria faces various biological obstacles, including the resistance of parasites to anti-malarial drugs and the resistance of mosquito vectors to insecticides. The resistance of Anopheles gambiae sensu lato (s.l.) to pyrethroids, the only class of insecticides used to impregnate mosquito nets, is known in Benin; the expansion of this resistance is influenced by the existence of gene flow between species, otherwise by the presence or absence of the kdr mutation in them. The objective of this study is to determine the spatial distribution of An. gambiae and the level of expression of the pyrethroid resistance kdr gene in seven agro-ecological zones of Benin. Methods: The study was conducted in 18 localities belonging to seven agro-ecological zones where environmental parameters varied. The sites represent the main areas of eco-epidemiological malaria in Benin. Anopheles gambiae larvae were collected in natural breeding sites using ladles and dipping method and reared under standard conditions. These larvae were reared under standard conditions of temperature and humidity (26 to 30 °C and 60 to 90%) at the insectarium of the Centre de Recherche Entomologique de Cotonou (CREC). Adult female mosquitoes having emerged are morphologically and molecularly identified. Homozygous resistant (1014F/1014F), homozygous sensitive (1014L/1014L) and heterozygous (1014F/1014L) genotypes of the L1014Fkdr gene mutation are determined by PCR. Results: A total of 677 An. gambiae was subjected at the PCR. The results revealed the presence of three vector species of the An. gambiae complex, of which 409 Anopheles coluzzii, 259 An.gambiae, 5 hybrids (An. coluzzii/An. gambiae) and 4 Anopheles arabiensis in the different agro-ecological zones. The four An. arabiensis were only found in Dassa, a locality in the cotton zone of central Benin. The frequency of distribution of the L1014F allele of the kdr gene varies from 84.48 to 100% in An. gambiae, from 80 to 100% in An. coluzzii and from 0 to 75% in An. arabiensis in the different agro-ecological zones. Moreover, a significant difference is generally observed in the distribution of the L1014F allele (P < 0.05). By comparing in pairs the distribution frequencies of this allele in the two species by agro-ecological zone, only a significant difference is noted in the central cotton and fishery zones (P = 0.0496). Conclusion: In summary, even if the data are in small portions, the An. Arabiensis species was found only in central Benin and the L1014F allele of the kdr gene is widespread and seems to fix in all the species recorded in the different agro-ecological zones. This situation amplifies the problem of resistance, which could eventually be a significant obstacle for the malaria vectors control. Similarly, a study of their genetic structure via the L1014F allele is necessary in order to put in place strategies to manage this resistance. These strategies will take into account both the ecology and the genetic diversity of the organisms involved to preserve the effectiveness of pyrethroids, the only insecticides used for the impregnation of mosquito nets. [ABSTRACT FROM AUTHOR]

Background: Malaria control through use of long-lasting insecticidal nets (LN) is threatened by the selection of anopheline mosquitoes strongly resistant to pyrethroid insecticides. To sustain future effectiveness it is essential to identify and evaluate novel insecticides suitable for nets. Mixtures of two insecticides with contrasting mode of action have the potential to kill resistant vectors and restore transmission control provided the formulation can withstand regular washing over the net’s life span. Method: The efficacy of a novel mixture LN, Interceptor® G2, that combines the pyrrole chlorfenapyr and pyrethroid alpha-cypermethrin was evaluated under controlled household conditions (experimental hut trial) and by laboratory bioassay against pyrethroid resistant An. gambiae in Benin before and after standardized washing. Comparison arms included standard alpha-cypermethrin LN, nets hand-treated with chlorfenapyr-only and untreated nets. Results: The chlorfenapyr-alphacypermethrin LN demonstrated improved efficacy and wash resistance compared to a standard alpha-cypermethrin LN against pyrethroid resistant mosquitoes (resistance ratio 207). In experimental hut trial alpha-cypermethrin LN killed only 20% (95% CI 15–26%) of host-seeking An. gambiae whilst mixture LN killed 71% (95% CI 65–77%). Mixture LN washed 20 times killed 65% (95% CI 58–71%), and thus intensive washing reduced efficacy by only 6% (95% CI 1.3–11%). The chlorfenapyr net killed 76% (95% CI 70–81%). Personal protection and blood feeding inhibition did not differ between mixture and pyrethroid LN; however, the mixture LN was 2.5 (95% CI: 2.1–3.1) times more protective than untreated nets. Standard WHO cone bioassays conducted during day time hours failed to anticipate field efficacy but overnight tunnel tests successfully predicted mixture LN and chlorfenapyr net efficacy in field trials. Conclusion: Interceptor® G2 LN demonstrates the potential to control transmission and provide community protection over the normal lifespan of long lasting nets where standard pyrethroid LN show signs of failing due to resistance. [ABSTRACT FROM AUTHOR]

Background: Malaria remains a pervasive public health problem in sub-Saharan West Africa. Here mosquito vector populations were explored across four sites in Mali and the Republic of Guinea (Guinea Conakry). The study samples the major ecological zones of malaria-endemic regions in West Africa within a relatively small distance. Methods: Mosquito vectors were sampled from larval pools, adult indoor resting sites, and indoor and outdoor human-host seeking adults. Mosquitoes were collected at sites spanning 350 km that represented arid savannah, humid savannah, semi-forest and deep forest ecological zones, in areas where little was previously known about malaria vector populations. 1425 mosquito samples were analysed by molecular assays to determine species, genetic attributes, blood meal sources and Plasmodium infection status. Results: Anopheles gambiae and Anopheles coluzzii were the major anophelines represented in all collections across the ecological zones, with A. coluzzii predominant in the arid savannah and A. gambiae in the more humid sites. The use of multiple collection methodologies across the sampling sites allows assessment of potential collection bias of the different methods. The L1014F kdr insecticide resistance mutation (kdr-w) is found at high frequency across all study sites. This mutation appears to have swept almost to fixation, from low frequencies 6 years earlier, despite the absence of widespread insecticide use for vector control. Rates of human feeding are very high across ecological zones, with only small fractions of animal derived blood meals in the arid and humid savannah. About 30 % of freshly blood-fed mosquitoes were positive for Plasmodium falciparum presence, while the rate of mosquitoes with established infections was an order of magnitude lower. Conclusions: The study represents detailed vector characterization from an understudied area in West Africa with endemic malaria transmission. The deep forest study site includes the epicenter of the 2014 Ebola virus epidemic. With new malaria control interventions planned in Guinea, these data provide a baseline measure and an opportunity to assess the outcome of future interventions. [ABSTRACT FROM AUTHOR]

Background: The genome-wide association study (GWAS) techniques that have been used for genetic mapping in other organisms have not been successfully applied to mosquitoes, which have genetic characteristics of high nucleotide diversity, low linkage disequilibrium, and complex population stratification that render population-based GWAS essentially unfeasible at realistic sample size and marker density. Methods: We designed a novel mapping strategy for the mosquito system that combines the power of linkage mapping with the resolution afforded by genetic association. We established founder colonies from West Africa, controlled for diversity, linkage disequilibrium and population stratification. Colonies were challenged by feeding on the infectious stage of the human malaria parasite, Plasmodium falciparum, mosquitoes were phenotyped for parasite load, and DNA pools for phenotypically similar mosquitoes were Illumina sequenced. Phenotype-genotype mapping was carried out in two stages, coarse and fine. Results: In the first mapping stage, pooled sequences were analysed genome-wide for intervals displaying relativereduction in diversity between phenotype pools, and candidate genomic loci were identified for influence upon parasite infection levels. In the second mapping stage, focused genotyping of SNPs from the first mapping stage was carried out in unpooled individual mosquitoes and replicates. The second stage confirmed significant SNPs in a locus encoding two Toll-family proteins. RNAi-mediated gene silencing and infection challenge revealed that TOLL 11 protects mosquitoes against P. falciparum infection. Conclusions: We present an efficient and cost-effective method for genetic mapping using natural variation segregating in defined recent Anopheles founder colonies, and demonstrate its applicability for mapping in a complex non-model genome. This approach is a practical and preferred alternative to population-based GWAS for first-pass mapping of phenotypes in Anopheles. This design should facilitate mapping of other traits involved in physiology, epidemiology, and behaviour. [ABSTRACT FROM AUTHOR]

Background: Globally, regions at the highest risk for emerging infectious diseases are often the ones with the fewest resources. As a result, implementing sustainable infectious disease surveillance systems in these regions is challenging. The cost of these programs and difficulties associated with collecting, storing and transporting relevant samples have hindered them in the regions where they are most needed. Therefore, we tested the sensitivity and feasibility of a novel surveillance technique called xenosurveillance. This approach utilizes the host feeding preferences and behaviors of Anopheles gambiae, which are highly anthropophilic and rest indoors after feeding, to sample viruses in human beings. We hypothesized that mosquito bloodmeals could be used to detect vertebrate viral pathogens within realistic field collection timeframes and clinically relevant concentrations. Methodology/Principal Findings: To validate this approach, we examined variables influencing virus detection such as the duration between mosquito blood feeding and mosquito processing, the pathogen nucleic acid stability in the mosquito gut and the pathogen load present in the host's blood at the time of bloodmeal ingestion using our laboratory model. Our findings revealed that viral nucleic acids, at clinically relevant concentrations, could be detected from engorged mosquitoes for up to 24 hours post feeding by qRT-PCR. Subsequently, we tested this approach in the field by examining blood from engorged mosquitoes from two field sites in Liberia. Using next-generation sequencing and PCR we were able to detect the genetic signatures of multiple viral pathogens including Epstein-Barr virus and canine distemper virus. Conclusions/Significance: Together, these data demonstrate the feasibility of xenosurveillance and in doing so validated a simple and non-invasive surveillance tool that could be used to complement current biosurveillance efforts. Author Summary: The emergence of infectious diseases can have devastating public health and economic consequences. Being able to identify such events at early stages could significantly mitigate some of these outcomes. In many resource poor regions of the world, current surveillance methods are hindered by the costs associated with collecting, storing and shipping clinical specimens. Herein we present a novel surveillance approach termed xenosurveillance that addresses some of these hurdles. Specifically, we leverage the feeding behavior of mosquitoes to sample human blood, which is then preserved on filter cards. Our laboratory studies demonstrated that such an approach can be used to detect vertebrate viral pathogens within realistic field collection timeframes at clinically relevant concentrations. Subsequently, we tested the feasibility of xenosurveillance in West Africa and found the presence of two vertebrate viral pathogens, Epstein Barr virus and canine distemper virus. Together, these data demonstrate the feasibility of xenosurveillance and suggest that it could be used to detect and predict pathogen outbreaks at earlier, more actionable stages of emergence. [ABSTRACT FROM AUTHOR]

The Anopheles gambiae complex of mosquitoes includes malaria vectors at different stages of speciation, whose study enables a better understanding of how adaptation to divergent environmental conditions leads to evolution of reproductive isolation. We investigated the population genetic structure of closely related sympatric taxa that have recently been proposed as separate species ( An. coluzzii and An. gambiae), sampled from diverse habitats along the Gambia river in West Africa. We characterized putatively neutral microsatellite loci as well as chromosomal inversion polymorphisms known to be associated with ecological adaptation. The results revealed strong ecologically associated population subdivisions within both species. Microsatellite loci on chromosome-3L revealed clear differentiation between coastal and inland populations, which in An. coluzzii is reinforced by a unusual inversion polymorphism pattern, supporting the hypothesis of genetic divergence driven by adaptation to the coastal habitat. A strong reduction of gene flow was observed between An. gambiae populations west and east of an extensively rice-cultivated region apparently colonized exclusively by An. coluzzii. Notably, this 'intraspecific' differentiation is higher than that observed between the two species and involves also the centromeric region of chromosome-X which has previously been considered a marker of speciation within this complex, possibly suggesting that the two populations may be at an advanced stage of differentiation triggered by human-made habitat fragmentation. These results confirm ongoing ecological speciation within these most important Afro-tropical malaria vectors and raise new questions on the possible effect of this process in malaria transmission. [ABSTRACT FROM AUTHOR]

Objective Insecticide resistance molecular markers can provide sensitive indicators of resistance development in Anopheles vector populations. Assaying these makers is of paramount importance in the resistance monitoring programme. We investigated the presence and distribution of knock-down resistance ( kdr) mutations in Anopheles gambiae s.l. in Tanzania. Methods Indoor-resting Anopheles mosquitoes were collected from 10 sites and tested for insecticide resistance using the standard WHO protocol. Polymerase chain reaction-based molecular diagnostics were used to genotype mosquitoes and detect kdr mutations. Results The An. gambiae tested were resistance to lambdacyhalothrin in Muheza, Arumeru and Muleba. Out of 350 An. gambiae s.l. genotyped, 35% were An. gambiae s.s. and 65% An. arabiensis. L1014S and L1014F mutations were detected in both An. gambiae s.s. and An. arabiensis. L1014S point mutation was found at the allelic frequency of 4-33%, while L1014F was at the allelic frequency 6-41%. The L1014S mutation was much associated with An. gambiae s.s. (χ2 = 23.41; P < 0.0001) and L1014F associated with An. arabiensis (χ2 = 11.21; P = 0.0008). The occurrence of the L1014S allele was significantly associated with lambdacyhalothrin resistance mosquitoes (Fisher exact P < 0.001). Conclusion The observed co-occurrence of L1014S and L1014F mutations coupled with reports of insecticide resistance in the country suggest that pyrethroid resistance is becoming a widespread phenomenon among our malaria vector populations. The presence of L1014F mutation in this East African mosquito population indicates the spreading of this gene across Africa. The potential operational implications of these findings on malaria control need further exploration. [ABSTRACT FROM AUTHOR]

Introduction: The efficacy of Vectobac GR (potency 200 ITU/mg), a new formulation of bacterial larvicide Bacillus thuringiensis var. israelensis Strain AM65-52, was evaluated against Anopheles gambiae and Culex quinquefasciatus in simulated field and natural habitats in Benin. Methods: In simulated field conditions, Vectobac GR formulation was tested at 3 dosages (0.6, 0.9, 1.2 g granules/m2 against An. gambiae and 1, 1.5, 2 g granules/m2 against Cx. quinquefasciatus) according to manufacturer’s product label recommendations. The dosage giving optimum efficacy under simulated field conditions were evaluated in the field. The efficacy of Vectobac GR in terms of emergence inhibition in simulated field conditions and of reduction of larval and pupal densities in rice fields and urban cesspits was measured following WHO guidelines for testing and evaluation of mosquito larvicides. Results: Vectobac GR caused emergence inhibition of ≥80% until 21 [20]–[22] days for An. gambiae at 1.2 g/m2 dose and 28 [27–29] days for Cx. quinquefasciatus at 2 g/m2 in simulated field habitats. The efficacy of Vectobac GR in natural habitats was for 2 to 3 days against larvae and up to 10 days against pupae. Conclusions: Treatment with Vectobac GR caused complete control of immature mosquito within 2–3 days but did not show prolonged residual action. Larviciding can be an option for malaria and filariasis vector control particularly in managing pyrethroid-resistance in African malaria vectors. Since use of larvicides among several African countries is being emphasized through Economic Community of West Africa States, their epidemiological impact should be carefully investigated. [ABSTRACT FROM AUTHOR]

Background: The effectiveness of insecticide treated nets is under threat across Africa south of the Sahara from the selection of pyrethroid resistance in Anopheles gambiae mosquitoes. To maintain progress against malaria it is necessary to identify alternative residual insecticides for mosquito nets. Mixtures of pyrethroid and insecticides with novel mode of action provide scope for both improved control and management of resistance through concurrent exposure to unrelated insecticides. Methods: The pyrrole chlorfenapyr and the pyrethroid alphacypermethrin were tested individually and as a mixture on mosquito nets in an experimental hut trial in southern Benin against pyrethroid resistant An gambiae and Culex quinquefasciatus mosquitoes. The nets were deliberately holed to simulate the effect of wear and tear. Results: The nets treated with the mixture of chlorfenapyr 200 mg/m2 and alphacypermethrin 25 mg/m2 killed a proportion of An gambiae (77%, 95%CI: 66–86%) significantly greater than nets treated with alphacypermethrin 25 mg/m2 (30%, 95%CI: 21–41%) but not significantly different from nets treated with chlorfenapyr 200 mg/m2 (69%, 95%CI: 57–78%). The nets treated with the mixtures procured personal protection against An gambiae biting(58–62%) by a greater margin than the alphacypermethrin treated net (39%), whereas the chlorfenapyr treated net was not protective. A similar trend in mortality and blood feeding inhibition between treatments was observed in Cx quinquefasciatus to that seen in An. gambiae, although the effects were lower. A mixture of alphacypermethrin with chlorfenapyr applied at 100 mg/m2 had an effect similar to the mixture with chlorfenapyr at 200 mg/m2. Conclusion: The effectiveness of ITNs against pyrethroid resistant mosquitoes was restored by the mixture: the alphacypermethrin component reduced human-vector contact while the chlorfenapyr controlled pyrethroid-resistant mosquitoes. The complementary action of these unrelated insecticides demonstrates that the combination on nets has potential for preventing malaria transmission in areas compromised by the spread of pyrethroid resistance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Evolution toward insecticide resistance in An. gambiae is probably related to the current use of insecticides in agriculture. [•] We identified species and sub species in B. tabaci and An. gambiae s.l. [•] We reviewed phenotypical and genotypical data on B. tabaci and An. gambiae. [•] kdr and ace1-R mutations were both detected in B. tabaci and An. gambiae. [ABSTRACT FROM AUTHOR]

The molecular form composition of Anopheles gambiae Giles s.s. (Diptera: Culicidae) mating swarms and the associated mating pairs ( copulae) were investigated during two rainy seasons (July to October, 2005 and July to November, 2006) in the villages of Soumousso and Vallée du Kou (VK7). Although the habitats of these villages differ markedly, sympatric populations of M and S molecular forms of An. gambiae s.s. occur in both places periodically. The main aim was to assess the degree to which these molecular forms mate assortatively. In Soumousso, a wooded savannah habitat, the majority of swarm samples consisted of only S-form males (21/28), although a few M-form males were found in mixed M- and S-form swarms. In VK7, a rice growing area, the majority of swarm samples consisted of only M-form males (38/62), until October and November 2006, when there were nearly as many mixed-form as single-form swarms. Overall, ∼60% of M- and S-form swarms were temporally or spatially segregated; the two forms were effectively prevented from encountering each other. Of the remaining 40% of swarms, however, only about half were single-form and the rest were mixed-form. Of the 33 copulae collected from mixed-form swarms, only four were mixed-form pairs, significantly fewer than expected by random pairing between forms ( χ2 = 10.34, d.f. = 2, P < 0.01). Finally, all specimens of inseminated females were of the same form as the sperm contained within their spermatheca ( n = 91), even for the four mixed-form copulae. These findings indicate that assortative mating occurs within mixed-form swarms, mediated most probably by close-range mate recognition cues. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the occurrence of the L1014F and L1014S kdr mutations in malaria vector populations in Burkina Faso (West Africa). A cross-sectional survey was conducted at 10 sites all located in cotton cultivation areas which are assumed to be the major insecticide resistance selection foci in Burkina Faso. The hot ligation method was used to detect the two kdr mutations in field collected Anopheles gambiae s.l. samples. For the first time in Burkina Faso the L1014S mutation was identified in both M and S forms of An. gambiae s.s. populations collected from the site of Koupela in the central-eastern region at low frequency. Furthermore, the L1014S mutation was also found in one specimen of An. arabiensis collected from the Dano site. The data generated in this study provides additional evidence of the spread of the L1014S mutation into An. gambiae s.l. populations in West Africa. It is now important to evaluate the role of the L1014S mutation in the pyrethroid resistance phenotype and assess its potential impact on the efficacy of pyrethroid-based control measures in West Africa where several resistance mutations now coexist. [Copyright &y& Elsevier]

In West Africa, M and S molecular forms of Anopheles gambiae sensu stricto (Diptera: Culicidae) Giles, frequently occur together, although with different population bionomics. The S form typically breeds in rain-dependant water collections and is present during the rainy season only whereas the M form can thrive all year long in areas with permanent breeding opportunities. In the present study, we explored physiological and developmental trade-offs at play in laboratory colonies and field populations of the M and S forms that originated from an area of sympatry in Burkina Faso, where M and S larvae exhibit such habitat segregation. In the laboratory, larvae of the M form developed slower than the S form (mean values 9.51 and 8.85 days, respectively, Wilcoxon's test, P < 0.001). Although wing length and dry weight at emergence showed large variations, M females were on average 8% heavier than S females of similar wing length. Higher nutritional reserves (proteins and lipids) in teneral adults explained part of this weight difference, reflecting a better ability of the M form to garner resources at the larval stage. Furthermore, a higher rate of ovarian maturation was observed in the M form after a single bloodmeal. The relevance of these findings for parasite transmission is discussed. [ABSTRACT FROM AUTHOR]

Anopheles gambiae M and S are thought to be undergoing ecological speciation by adapting to different larval habitats. Toward an improved understanding of the genetic determinants and evolutionary processes shaping their divergence, we used a 400,000 single-nucleotide polymorphism (SNP) genotyping array to characterize patterns of genomic differentiation between four geographically paired M and S population samples from West and Central Africa. In keeping with recent studies based on more limited genomic or geographic sampling, divergence was not confined to a few isolated “speciation islands.” Divergence was both widespread across the genome and heterogeneous. Moreover, we find consistent patterns of genomic divergence across sampling sites and mutually exclusive clustering of M and S populations using genetic distances based on all 400,000 SNPs, implying that M and S are evolving collectively across the study area. Nevertheless, the clustering of local M and S populations using genetic distances based on SNPs from genomic regions of low differentiation is consistent with recent gene flow and introgression. To account for these data and reconcile apparent paradoxes in reported patterns of M–S genomic divergence and hybridization, we propose that extrinsic ecologically based postmating barriers vary in strength as environmental conditions fluctuate or change. [ABSTRACT FROM AUTHOR]

Anopheles melas is a brackish water-breeding member of the Anopheles gambiae complex that is distributed along the coast of West Africa and is a major malaria vector within its range. Because little is known about the population structure of this species, we analysed 15 microsatellite markers and 1161 bp of mt DNA in 11 A. melas populations collected throughout its range. Compared with its sibling species A. gambiae, A. melas populations have a high level of genetic differentiation between them, representing its patchy distribution due to its fragmented larval habitat that is associated with mangroves and salt marsh grass. Populations clustered into three distinct groups representing Western Africa, Southern Africa and Bioko Island populations that appear to be mostly isolated. Fixed differences in the mt DNA are present between all three clusters, and a Bayesian clustering analysis of the microsatellite data found no evidence for migration from mainland to Bioko Island populations, and little migration was evident between the Southern to the Western cluster. Surprisingly, mt DNA divergence between the three A. melas clusters is on par with levels of divergence between other species of the A. gambiae complex, and no support for monophyly was observed in a maximum-likelihood phylogenetic analysis. Finally, an approximate Bayesian analysis of microsatellite data indicates that Bioko Island A. melas populations were connected to the mainland populations in the past, but became isolated, presumably when sea levels rose after the last glaciation period (≥10 000-11 000 bp). This study has exposed species-level genetic divergence within A. melas and also has implications for control of this malaria vector. [ABSTRACT FROM AUTHOR]

The article presents the findings of a study on the behavioural responses of anopheles gambiae sensu stricto M and S molecular form larvae to an aquatic predator in Burkina Faso. It discusses the methodology used for conducting the study. It mentions that the behaviour of M and S form larvae was found to differ significantly. It informs that larvae used in these experiments were obtained from eggs laid by wild female anopheles gambiae. It concludes that behavioural differences between larvae of the M and S form of gambiae in response to an acute predation risk is likely to be a reflection of different trade-offs between foraging and predator vigilance that might be of adaptive value in contrasting aquatic ecosystems.

The direction and magnitude of movement by the malaria vector Anopheles gambiae Giles has been of great interest to medical entomologists for over 70 years. This direction of movement is likely to be affected by many factors, from environmental conditions and stage of life history of the mosquito to the existence of attractants in the vicinity. We report here the direction of movement of newly emerged An. gambiae in nature, around the village of Donéguébougou, Mali. We assessed the direction of movement for individual mosquitoes by placing them in a novel enclosure with exit traps oriented in the direction of the cardinal and intermediate points of the compass. We consistently found predominantly Southward directions of movement during 2009 and 2010, with an additional Eastward component during the dry season and a Westward one during the wet season. Our data indicate that wind has an important effect on the direction of movement, but that this effect varied by season: Average directions of movement were downwind during the dry season and upwind during the wet season. A switch in anemotactic response suggests that the direction of movement of An. gambiae relative to the wind immediately after emergence under varying conditions of humidity should be further investigated under controlled conditions. [ABSTRACT FROM AUTHOR]

Background: Increasing incidences of insecticide resistance in malaria vectors are threatening the sustainable use of contemporary chemical vector control measures. Fungal entomopathogens provide a possible additional tool for the control of insecticide-resistant malaria mosquitoes. This study investigated the compatibility of the pyrethroid insecticide permethrin and two mosquito-pathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, against a laboratory colony and field population of West African insecticide-resistant Anopheles gambiae s.s. mosquitoes. Methodology/Findings: A range of fungus-insecticide combinations was used to test effects of timing and sequence of exposure. Both the laboratory-reared and field-collected mosquitoes were highly resistant to permethrin but susceptible to B. bassiana and M. anisopliae infection, inducing 100% mortality within nine days. Combinations of insecticide and fungus showed synergistic effects on mosquito survival. Fungal infection increased permethrin-induced mortality rates in wild An. gambiae s.s. mosquitoes and reciprocally, exposure to permethrin increased subsequent fungal-induced mortality rates in both colonies. Simultaneous co-exposure induced the highest mortality; up to 70.3±2% for a combined Beauveria and permethrin exposure within a time range of one gonotrophic cycle (4 days). Conclusions/Significance: Combining fungi and permethrin induced a higher impact on mosquito survival than the use of these control agents alone. The observed synergism in efficacy shows the potential for integrated fungus-insecticide control measures to dramatically reduce malaria transmission and enable control at more moderate levels of coverage even in areas where insecticide resistance has rendered pyrethroids essentially ineffective. [ABSTRACT FROM AUTHOR]

Abstract: Resistance to the organophosphate and carbamate insecticides through insensitivity of the target site enzyme, acetylcholinesterase has recently been reported in Anopheles gambiae populations in West Africa. To date, screening for the mutation (G119S of the ace-1 gene) conferring this insensitivity has employed a simple PCR-RFLP diagnostic. However, this has the disadvantage of requiring digestion of the amplified fragment and subsequent gel electrophoresis of the products. To overcome this, and thus increase throughput and reduce costs, we have developed two assays based on real-time PCR (TaqMan and melt-curve) that represent true ‘closed-tube’ approaches. The two new platforms were compared to PCR-RFLP to genotype over 280 samples. The two new methods compared favourably with PCR-RFLP with the TaqMan assay delivering the greatest specificity and sensitivity of the three approaches. This assay is also cheaper to run than PCR-RFLP and results are obtained in a single step. [Copyright &y& Elsevier]

Background: The G119S mutation responsible for insensitive acetylcholinesterase resistance to organophosphate and carbamate insecticides has recently been reported from natural populations of Anopheles gambiae in West Africa. These reports suggest there are costs of resistance associated with this mutation for An. gambiae, especially for homozygous individuals, and these costs could be influential in determining the frequency of carbamate resistance in these populations. Methods: Life-history traits of the AcerKis and Kisumu strains of An. gambiae were compared following the manipulation of larval food availability in three separate experiments conducted in an insecticide-free laboratory environment. These two strains share the same genetic background, but differ in being homozygous for the presence or absence of the G119S mutation at the ace-1 locus, respectively. Results: Pupae of the resistant strain were significantly more likely to die during pupation than those of the susceptible strain. Ages at pupation were significantly earlier for the resistant strain and their dry starved weights were significantly lighter; this difference in weight remained when the two strains were matched for ages at pupation. Conclusions: The main cost of resistance found for An. gambiae mosquitoes homozygous for the G119S mutation was that they were significantly more likely to die during pupation than their susceptible counterparts, and they did so across a range of larval food conditions. Comparing the frequency of G119S in fourth instar larvae and adults emerging from the same populations would provide a way to test whether this cost of resistance is being expressed in natural populations of An. gambiae and influencing the dynamics of this resistance mutation. [ABSTRACT FROM AUTHOR]

Background: Anopheles gambiae sensu stricto, one of the principal vectors of malaria, has been divided into two subspecific groups, known as the M and S molecular forms. Recent studies suggest that the M form found in Cameroon is genetically distinct from the M form found in Mali and elsewhere in West Africa, suggesting further subdivision within that form. Methods: Chromosomal, microsatellite and geographic/ecological evidence are synthesized to identify sources of genetic polymorphism among chromosomal and molecular forms of the malaria vector Anopheles gambiae s.s. Results: Cytogenetically the Forest M form is characterized as carrying the standard chromosome arrangement for six major chromosomal inversions, namely 2La, 2Rj, 2Rb, 2Rc, 2Rd, and 2Ru. Bayesian clustering analysis based on molecular form and chromosome inversion polymorphisms as well as microsatellites describe the Forest M form as a distinct population relative to the West African M form (Mopti-M form) and the S form. The Forest-M form was the most highly diverged of the An. gambiae s.s. groups based on microsatellite markers. The prevalence of the Forest M form was highly correlated with precipitation, suggesting that this form prefers much wetter environments than the Mopti-M form. Conclusion: Chromosome inversions, microsatellite allele frequencies and habitat preference all indicate that the Forest M form of An. gambiae is genetically distinct from the other recognized forms within the taxon Anopheles gambiae sensu stricto. Since this study covers limited regions of Cameroon, the possibility of gene flow between the Forest-M form and Mopti-M form cannot be rejected. However, association studies of important phenotypes, such as insecticide resistance and refractoriness against malaria parasites, should take into consideration this complex population structure. [ABSTRACT FROM AUTHOR]

Background: The role of inter-specific hybridisation is of particular importance in mosquito disease vectors for predicting the evolution of insecticide resistance. Two molecular forms of Anopheles gambiae s.s., currently recognized as S and M taxa, are considered to be incipient sibling species. Hybrid scarcity in the field was suggested that differentiation of M and S taxa is maintained by limited or absent gene flow. However, recent studies have revealed shared polymorphisms within the M and S forms, and a better understanding of the occurrence of gene flow is needed. One such shared polymorphism is the G119S mutation in the ace-1 gene (which is responsible for insecticide resistance); this mutation has been described in both the M and S forms of A. gambiae s.s. Methods and Results: To establish whether the G119S mutation has arisen independently in each form or by genetic introgression, we analysed coding and non-coding sequences of ace-1 alleles in M and S mosquitoes from representative field populations. Our data revealed many polymorphic sites shared by S and M forms, but no diversity was associated with the G119S mutation. These results indicate that the G119S mutation was a unique event and that genetic introgression explains the observed distribution of the G119S mutation within the two forms. However, it was impossible to determine from our data whether the mutation occurred first in the S form or in the M form. Unexpectedly, sequence analysis of some resistant individuals revealed a duplication of the ace-1 gene that was observed in both A. gambiae s.s. M and S forms. Again, the distribution of this duplication in the two forms most likely occurred through introgression. Conclusions: These results highlight the need for more research to understand the forces driving the evolution of insecticide resistance in malaria vectors and to regularly monitor resistance in mosquito populations of Africa. [ABSTRACT FROM AUTHOR]

The pyrethroid knockdown resistance gene (kdr) has become widespread in Anopheles gambiae in West Africa. A trial to test the continuing efficacy of insecticide-treated nets (ITN) and indoor residual spraying (IRS) was undertaken in experimental huts at 2 sites in Benin, the first where kdr is present at high frequency (Ladji), the second-where An. gambiae is susceptible (Malanville). Holes were made in the nets to mimic worn nets. At Malanville, 96% of susceptible An. gambiae were inhibited from blood-feeding, whereas at Ladji feeding was uninhibited by ITNs. The mortality rate of An. gambiae in ITN huts was 98% in Malanville but only 30% at Ladji. The efficacy of IRS was equally compromised. Mosquitoes at Ladji had higher oxidase and esterase activity than in a laboratory-susceptible strain, but this fact did not seem to contribute to resistance. Pyrethroid resistance in An. gambiae appears to threaten the future of ITN and IRS in Benin. [ABSTRACT FROM AUTHOR]

Background: Genetic linkage mapping identified a region of chromosome 2L in the Anopheles gambiae genome that exerts major control over natural infection by Plasmodium falciparum. This 2L Plasmodium-resistance interval was mapped in mosquitoes from a natural population in Mali, West Africa, and controls the numbers of P. falciparum oocysts that develop on the vector midgut. An important question is whether genetic variation with respect to Plasmodium-resistance exists across Africa, and if so whether the same or multiple geographically distinct resistance mechanisms are responsible for the trait. Methods: To identify P falciparum resistance loci in pedigrees generated and infected in Kenya, East Africa, 28 microsatellite loci were typed across the mosquito genome. Genetic linkage mapping was used to detect significant linkage between genotype and numbers of midgut oocysts surviving to 7-8 days post-infection. Results: A major malaria-control locus was identified on chromosome 2L in East African mosquitoes, in the same apparent position originally identified from the West African population. Presence of this resistance locus explains 75% of parasite free mosquitoes. The Kenyan resistance locus is named EA̱Pfin1 (East Africa̱ Plasmodium falciparum Infection Intensity). Conclusion: Detection of a malaria-control locus at the same chromosomal location in both East and West African mosquitoes indicates that, to the level of genetic resolution of the analysis, the same mechanism of Plasmodium-resistance, or a mechanism controlled by the same genomic region, is found across Africa, and thus probably operates in A. gambiae throughout its entire range. [ABSTRACT FROM AUTHOR]

We conducted laboratory tests to assess the sensitivity to the insect repellent 1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-, 1-methylpropylester (known as KBR 3023 or Picaridin, trade name Bayrepel) of West African strains of the yellow fever mosquito Aedes aegypti and of malaria vectors of the Anopheles gambiae complex, in comparison with the standard repellent N,N-diethyl-3-methyl-benzamide (DEET). Test mosquitoes were exposed according to a 'separate arms' protocol to logarithmic dose increments applied on one arm of human subjects to evaluate the relative potency, and the median effective dosages (ED50 and ED90). According to a logistic regression model fitted to the experimental data, the dose-response relationship for the two repellents was the same within each species, thus pooled ED values were assessed for each mosquito separately. The median ED of KBR 3023 and DEET was estimated at 0.78 (95% confidence limits (CI): 0.57-1.04) and at 0.018 microg/cm2 (0.004-0.052) for mosquitoes of the An. gambiae complex and Ae. aegypti, respectively. ED90 values were 125.6 (81.4-201.3) and 24.0 microg/cm2 (5.7-208.5) for An. gambiae s.l. and Ae. aegypti, respectively. The relative potency of KBR 3023 was not significantly different from that of DEET for An. gambiae s.l. (95% confidence limits 0.7-1.0), whereas in the case of Ae. aegypti it was with 95% probability 1.1-2.0 times more potent than DEET. On the basis of available evidence, KBR 3023 represents a promising alternative to DEET for personal protection against bites of these important vectors of disease in the Afrotropical region. [ABSTRACT FROM AUTHOR]

Seven cross-sectional entomological surveys were carried out from September 1995 to February 1998 in three irrigated rice growing villages and three villages without irrigated agriculture in the area surrounding Niono, located 350 km north-east of Bamako, Mali. The transmission pattern differed markedly between the two zones. In the irrigated zone, the transmission of malaria was fairly constant over the seasons at a low level. In the non-irrigated zone, transmission was mostly below detection level during the dry season, whereas it was high toward the end of the rainy season. In the irrigated zone, high densities of mosquitoes were correlated with low anthropophily, low sporozoite indices and probably low survival rates. In the non-irrigated zone, mosquito densities were lower and these relationships were less pronounced. Differential use of mosquito nets in the two zones may have been an important factor in the observed differences in transmission. The presence of cattle may also have played an important role. Two mosquito-catching methods (human landing catch and spray catch) were compared. [Copyright &y& Elsevier]