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Abstract Background Historical studies have indicated that An. gambiae s.s. is the predominant malaria vector species in Bobo-Dioulasso the second biggest city of Burkina Faso (West Africa). However, over the last decade, An. arabiensis appears to be replacing An. gambiae s.s. as the most prevalent malaria vector in this urban setting. To investigate this species transition in more detail the present study aims to provide an update on the malaria vector composition in Bobo-Dioulasso, and also the Plasmodium infection rates and susceptibility to insecticides of the local An. gambiae s.l. population. Methods An entomological survey was carried out from May to December 2008 in Dioulassoba and Kodeni (central and peripheral districts respectively), which are representative of the main ecological features of the city. Sampling consisted of the collection of larval stages from water bodies, and adults by monthly indoor residual spraying (IRS) using aerosol insecticides. Insecticide susceptibility tests were performed using the WHO filter paper protocol on adults emerged from larvae. PCR was used to determine vector species and to identify resistance mechanisms (kdr and ace-1R). The Plasmodium infection rate was estimated by ELISA performed on female mosquitoes collected indoors by IRS. Results An. arabiensis was found to be the major malaria vector in Bobo-Dioulasso, comprising 50 to 100% of the vector population. The sporozoite infection rate for An. arabiensis was higher than An. gambiae s.s. at both Dioulassoba and Kodeni. An. gambiae s.l. was resistant to DDT and cross-resistant to pyrethroids at the two sites with higher levels of resistance observed in An. gambiae s.s. than An. arabiensis. Resistance to 0.1% bendiocarb was observed in the An. gambiae s.s. S form but not the M form or in An. arabiensis. The L1014F kdr mutation was detected in the two molecular forms of An. gambiae s.s. at varying frequencies (0.45 to 0.92), but was not detected in An. arabiensis, suggesting that other mechanisms are involved in DDT resistance in this species. The ace-1R mutation was only detected in the S molecular form and was observed at the two sites at similar frequency (0.3). Conclusions Over the last ten years, An. arabiensis has become the major malaria vector in Bobo-Dioulasso city where it was formerly present only at low frequency. However, the ecological determinant that enhances the settlement of this species into urban and peri-urban areas of Bobo-Dioulasso remains to be clarified. The impact of the changing An. gambiae s.l. population in this region for vector control including resistance management strategies is discussed.

Background: Essential oils of Cymbopogon citratus and Hyptis suaveolens are known for their insecticidal properties, but remain ineffective against mosquitoes resistant to synthetic insecticides. In order to improve insecticidal properties of these plants, this study aimed to investigate the chemical composition and insecticidal activity against Anopheles gambiae mosquitoes of essential oil obtained by co-distillation of dry leaves of C. citratus and H. suaveolens., Methods: Essential oils were extracted by hydrodistillation from dry leaves of C. citratus and H. suaveolens, separately, then from the mixture of the dry leaves of the two plants in mass ratio 50/50. Each pure essential oil and the mixture obtained either by co-distillation or by combining pure essential oils in volume ratio 50/50 were then analysed by GC/MS. All essential oils and Deltamethrin 0.05% (positive control) were tested on two species of mosquitoes of the genus Anopheles gambiae according to the World Health Organization standard methods., Results: Essential oil obtained by co-distillation mainly contained piperitone (40.80%), 1,8-cineole (24.64%), p-menth-4(8)-ene (13.20%), limonene (6.09%) and α-pinene (4.73%). However, the mixture of pure essential oils of these two plants mostly contained geranial (20.74%), neral (16.42%), 1,8-cineole (19.79%), sabinene (6.03%) and β-pinene (3.87%). The essential oil of C. citratus mainly contained geranial (41.49%), neral (32.83%), β-myrcene (13.66%) and geraniol (3.49%) while the major constituents of essential oil of H. suaveolens were 1,8-cineole (39.58%), sabinene (12.06%), β-pinene (7.73%), α-terpinolene (6.72%) and (E)-caryophyllene (7.49%). At the dose of 1%, all essential oils, except that of H. suaveolens, induced about 100% of mortality on the sensitive species of An. gambiae. However, on the resistant species at the same dose, the essential oil obtained by co-distillation induced the highest mortality (53.44%). The essential oils of C. citratus, H. suaveolens and the mixture of the two pure essential oils caused respectively 2.47, 15.28 and 18.33% of mortality. The synthetic insecticide caused 100 and 14.84% of mortality respectively on the sensitive and resistant species of An. gambiae., Conclusion: Essential oil obtained by co-distillation showed good insecticidal efficacy against a resistant species of An. gambiae and might constitute a new solution to fight against mosquitoes resistant to synthetic insecticides., Competing Interests: Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Mosquitoes of the genus Aedes are the most important arthropod disease vector. Dengue virus (DENV) and Chikungunya virus (CHIKV) are the main arboviruses distributed throughout the world. Based on entomo-virological surveillance, appropriate public health strategies can be adopted to contain cases and control outbreaks. This study aims to show the potential performance of two new molecular methods for detecting DENV serotypes and CHIKV in mosquitoes. Mosquitoes were collected in urban and sylvatic areas of Bobo-Dioulasso, Burkina Faso, between July and August 2023. DENV and CHIKV were screened using new multiplex RT-PCR and RT-qPCR methods. A total of 2150 mosquitoes were trapped, consisting of 976 Aedes (959 Ae. aegypti , 6 Ae. furcifer , and 11 Ae. vittatus ) and 1174 Culex sp. These were grouped into 39 pools, with each pool containing a maximum of 30 mosquitoes. Molecular screening revealed that 7.7% (3/39) of the pools were positive for DENV. Specifically, DENV-1 was detected in one pool (1/3), and DENV-3 was found in two pools (2/3). All pools tested negative for CHIKV. The overall minimum infection rate (MIR) of DENV in this study was 3.07 (95% CI: 2.24-19.86). This study shows the usefulness of our new molecular tools for the surveillance of DENV serotypes and CHIKV.

Dengue vector control strategies are mostly based on chemicals use against Aedes aegypti populations. The current study aimed at investigating the insecticidal effects of essential oils (EOs) obtained from five plant species, Cymbopogon citrates (D. C.) Stapf. (Poaceae), Cymbopogon nardus (Linn.) Rendle (Poaceae), Eucalyptus camaldulensis Linn. (Myrtaceae), Lippia multiflora Moldenke (Verbenaceae), and Ocimum americanum Linn. Lamiaceae, and combinations of Cymbopogon nardus and Ocimum americanum on Ae. aegypti populations from Bobo-Dioulasso. For this purpose, adults of the susceptible and field strains of Ae. aegypti were tested in WHO tubes with EO alone and binary combinations of O. americanum (OA) and C. nardus (CN; scored from C1 to C9). The extraction of the essential oils was done by hydrodistillation, and their components were determined by GC/MS. Among the 5 EOs tested, L. multiflora essential oil was the most efficient, with KDT50 values below 60 min on all Ae. aegypti strains tested, and also with a rate of mortality up to 100 and 85% for Bora Bora and Bobo-Dioulasso strains, respectively. This efficacy may be due to its major compounds which are with major compounds as β-caryophyllene, p-cymene, thymol acetate, and 1.8 cineol. Interestingly, on all strains, C8 combination showed a synergistic effect, while C2 showed an additive effect. These combinations exhibit a rate of mortality varying from 80 to 100%. Their toxicity would be due to the major compounds and the putative combined effects of some major and minor compounds. More importanly, L. multiflora EO and combinations of C. nardus and O. americanum EO, may be used as alternatives against pyrethroid resistant of Ae. aegypti., (© The Author(s) 2022. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Targeting genes involved in sexual determinism, for vector or pest control purposes, requires a better understanding of their polymorphism in natural populations in order to ensure a rapid spread of the construct. By using genomic data from An. gambiae s.l., we analyzed the genetic variation and the conservation score of the fru gene in 18 natural populations across Africa. A total of 34,339 SNPs were identified, including 3.11% non-synonymous segregating sites. Overall, the nucleotide diversity was low, and the Tajima’s D neutrality test was negative, indicating an excess of low frequency SNPs in the fru gene. The allelic frequencies of the non-synonymous SNPs were low (freq < 0.26), except for two SNPs identified at high frequencies (freq > 0.8) in the zinc-finger A and B protein domains. The conservation score was variable throughout the fru gene, with maximum values in the exonic regions compared to the intronic regions. These results showed a low genetic variation overall in the exonic regions, especially the male sex-specific exon and the BTB-exon 1 of the fru gene. These findings will facilitate the development of an effective gene drive construct targeting the fru gene that can rapidly spread without encountering resistance in wild populations.

The persistence of malaria and the increasing of resistance of Anopheles gambiae species to chemicals remain major public health concerns in sub-Saharan Africa. Faced to these concerns, the search for alternative vector control strategies as use of essential oils (EOs) need to be implemented. Here, the five EOs from Cymbopogon citratus, Cymbopogon nardus, Eucalyptus camaldulensis, Lippia multiflora, Ocimum americanum obtained by hydro distillation were tested according to World Health Organization procedures on An. gambiae "Kisumu" and field strains collected in "Vallée du Kou". Also, the binary combinations of C. nardus (Cn) and O. americanum (Oa) were examined. As results, among the EOs tested, L. multiflora was the most efficient on both An. gambiae strains regarding KDT 50 (50% of mosquitoes knock down time) and KDT 95 and rate of morality values. Our current study showed that C8 (Cn 80%: Oa 20%) and C9 (Cn 90%: Oa 10%), were the most toxic to An. gambiae strain "Vallée de Kou" (VK) with the mortality rates reaching 80.7 and 100% at 1% concentration, respectively. These two binary combinations shown a synergistic effect on the susceptible population. However, only C9 gave a synergistic effect on VK population. The bioactivity of the two EOs, C. nardus and O. americanum, was improved by the combinations at certain proportions. The resistance ratios of all EOs and of the combinations were low (< 5). The combinations of C. nardus and O. americanum EOs at 90: 10 ratio and to a lesser extent L. multiflora EO, could be used as alternative bio-insecticides against malaria vectors resistant to pyrethroids in vector control programmes., (© 2022. The Author(s).)

Despite the implementation of different strategies to fight against malaria in Burkina Faso since 2005, it remains today the leading cause of hospitalization and death. Adapting interventions to the spatial and temporal distribution of malaria could help to reduce this burden. This study aims to determine the structure and stability of malaria hotspots in Burkina Faso, with the objective of adapting interventions at small geographical scales. Data on malaria cases from 2013 to 2020 were acquired at municipalities level. Municipality-wise malaria endemicity levels were mapped through geographical information system (GIS) tools. Spatial statistical analysis using Kulldoff sweeps were carried out to identify malaria hotspots. Then we mapped the monthly malaria risk. Malaria is endemic in all the municipalities of Burkina Faso. However, two stable main spatial clusters (South-Western and Eastern part of the country) are emerging with seasonal reinforcement. Interventions targeting the identified clusters could significantly reduce the incidence of malaria in Burkina Faso. This also prompts for further studies to identify the local determinants of this high transmission for the future success of malaria control., Competing Interests: The authors declare that there are no competing interests regarding the publication of this paper., (© 2022 The Authors.)

Every year, malaria kills approximately 405,000 people in Sub-Saharan Africa, most of them children under the age of five years. In many countries, progress in malaria control has been threatened by the rapid spread of resistance to antimalarial drugs and insecticides. Novel genetic mosquito control approaches could play an important role in future integrated malaria control strategies. In July 2019, the Target Malaria consortium proceeded with the first release of hemizygous genetically-modified (GM) sterile and non-transgenic sibling males of the malaria mosquito Anopheles coluzzii in Burkina Faso. This study aimed to determine the potential fitness cost associated to the transgene and gather important information related to the dynamic of transgene-carrying mosquitoes, crucial for next development steps. Bayesian estimations confirmed that GM males had lower survival and were less mobile than their wild type (WT) siblings. The estimated male population size in Bana village, at the time of the release was 28,000 - 37,000. These results provide unique information about the fitness and behaviour of released GM males that will inform future releases of more effective strains of the A. gambiae complex., (© 2022. The Author(s).)

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.

Background: Insecticide resistance has become a widespread problem causing a decline in the effectiveness of vector control tools in sub-Saharan Africa. In this situation, ongoing monitoring of vector susceptibility to insecticides is encouraged by the WHO to guide national malaria control programmes. Our study was conducted from April to November 2018 in Tchonka (Sud-Kivu, Democratic Republic of the Congo) and reported primary data on the resistance status of Anopheles funestus and Anopheles gambiae., Methods: Insecticide susceptibility bioassays were performed on wild populations of A. funestus and A. gambiae using WHO insecticide-impregnated papers at discriminating concentration. In addition, PCR was performed to identify mosquito species and to detect kdr and ace-1R mutations involved in insecticide resistance., Results: Bioassay results show resistance to all tested insecticides except pirimiphos-methyl, propoxur, fenitrothion and malathion with a mortality rate ranging from 95.48 to 99.86%. The addition of piperonyl butoxide (PBO) increased the susceptibility of vectors to deltamethrin and alpha-cypermethrin by exhibiting a mortality ranging from 91.50 to 95.86%. The kdr mutation was detected at high frequencies (approximately 0.98) within A. gambiae while ace-1R was not detected., Conclusions: This study provides useful data on the insecticide resistance profiles of malaria vector populations to better manage vector control. Our results highlight that, despite the high level of resistance, organophosphorus compounds and pyrethroids + PBO remain effective against the vectors., (© The Author(s) 2021. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene.)

Indoor residual spraying (IRS) was applied in addition to the use of long-lasting insecticidal nets in the South West in Burkina Faso, where Anopheles gambiae s.l. the major malaria vector was resistant to pyrethroids. This study was designed to evaluate the efficacy and residual life of bendiocarb (active ingredient) used for spraying on different wall surfaces (mud and cement). Cone bioassays were done monthly with the susceptible An. gambiae 'Kisumu' strain and the local wild populations to determine the duration for which insecticide was effective in killing mosquitoes. Cone bioassay data showed low efficacy and short persistence of bendiocarb applied on mud and cement walls, lasting 2 mo with the susceptible insectary strain and less than 1 mo with An. gambiae wild populations. In addition, WHO tube assays confirmed resistance of An. gambiae wild populations to 0.1% bendiocarb with mortality rates less than 80% in both study sites (sprayed and unsprayed sites). The pilot study of IRS with bendiocarb showed that the residual efficacy of bendiocarb was very short, and resistance to bendiocarb was confirmed in wild populations of An. gambiae s.l. Therefore, Ficam 80 WP was not suitable for IRS in this area due to the short residual duration related mainly to vectors resistance to bendiocarb. While waiting for innovative malaria control tool, alternative insecticide (organophosphate or neonicotinoid classes) or combinations of insecticides have to be used for insecticide resistance management in Burkina Faso., (© The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: This study reports an updated description on malaria vector diversity, behaviour, insecticide resistance and malaria transmission in the Diébougou and Dano peri-urban areas, Burkina Faso., Methods: Mosquitoes were caught monthly using CDC light traps and pyrethrum spray catches. Mosquitoes were identified using morphological taxonomic keys. PCR techniques were used to identify the species of the Anopheles gambiae complex and insecticide resistance mechanisms in a subset of Anopheles vectors. The Plasmodium sporozoite infection status and origins of blood meals of female mosquitoes were determined by ELISA methods. Larvae were collected, breed in the insectary and tested for phenotypic resistance against four insecticides using WHO bioassays., Results: This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management., Conclusions: This study contributed to update the entomological data in two peri-urban areas of Southwest Burkina Faso. Anopheles populations were mostly anthropophilic and endophilic in both areas and exhibit high susceptibility to an organophosphate insecticide. This offers an alternative for the control of these pyrethroid-resistant populations. These data might help the National Malaria Control Programme for decision-making about vector control planning and resistance management.

In West Africa, Aedes aegypti remains the major vector of dengue virus. Since 2013, dengue fever has been reemerging in Burkina Faso with annual outbreaks, thus becoming a major public health problem. Its control relies on vector control, which is unfortunately facing the problem of insecticide resistance. At the time of this study, although data on phenotypic resistance were available, information related to the metabolic resistance in Aedes populations from Burkina Faso remained very scarce. Here, we assessed the phenotypic and the metabolic resistance of Ae. aegypti populations sampled from the two main urban areas (Ouagadougou and Bobo-Dioulasso) of Burkina Faso. Insecticide susceptibility bioassays to chlorpyriphos-methyl 0.4%, bendiocarb 0.1% and deltamethrin 0.05% were performed on natural populations of Ae. aegypti using the WHO protocol. The activity of enzymes involved in the rapid detoxification of insecticides, especially non-specific esterases, oxidases (cytochrome P450) and glutathione-S-transferases, was measured on individual mosquitos. The mortality rates for deltamethrin 0.05% were low and ranged from 20.72% to 89.62% in the Bobo-Dioulasso and Ouagadougou sites, respectively. When bendiocarb 0.1% was tested, the mortality rates ranged from 7.73% to 71.23%. Interestingly, in the two urban areas, mosquitoes were found to be fully susceptible to chlorpyriphos-methyl 0.4%. Elevated activity of non-specific esterases and glutathione-S-transferases was reported, suggesting multiple resistance mechanisms involved in Ae. aegypti populations from Bobo-Dioulasso and Ouagadougou (including cytochrome P450). This update to the insecticide resistance status within Ae. aegypti populations in the two biggest cities is important to better plan dengue vectors control in the country and provides valuable information for improving vector control strategies in Burkina Faso, West Africa.

Background: In view of widespread pyrethroid resistance in malaria vectors in Africa, two long-lasting insecticidal nets (LLINs) incorporated with a synergist, piperonyl butoxide (PBO), DawaPlus 3.0 (deltamethrin + PBO in the roof panel; deltamethrin alone in the side panels) and DawaPlus 4.0 (deltamethrin + PBO in all panels), were evaluated in an experimental hut trial in a rice growing irrigated area in Burkina Faso. Efficacy of nets was tested against free-flying malaria vector, Anopheles gambiae s.l., with high pyrethroid resistance involving L1014F kdr and CYP6P3P450 resistance mechanisms., Methodology: The efficacy of unwashed and 20-times washed DawaPlus 3.0 (polyethylene roof panel with 120 mg/m2 deltamethrin and 440 mg/m2 PBO; polyester side panels with deltamethrin 100 mg/m2) and DawaPlus 4.0 (same composition as roof of DawaPlus 3.0) was evaluated against DawaPlus 2.0 (80 mg/m2 deltamethrin; positive control). Volunteer sleepers and treatments were rotated in huts using a Latin square design on 63 consecutive nights during August-October 2016. Mortality, human blood-feeding inhibition, deterrence and exit rates of An. gambiae s.l. were monitored., Principal Findings: Significantly higher rates of mortality and blood-feeding inhibition were observed with unwashed DawaPlus 4.0 (36%; 47.5%) than unwashed DawaPlus 3.0 (11.8%; 33.3%), DawaPlus 2.0 (4.3%; 6.4%) or untreated net (P < 0.05). Washing reduced personal protective efficacy yet PBO-LLINs were more protective and both met the WHO criteria., Conclusions: The PBO-containing DawaPlus 4.0 significantly protected against An. gambiae s.l. in the study area. Unwashed DawaPlus 3.0 gave low to moderate protection against the positive control. PBO inhibits oxidase action; hence in areas with active malaria transmission having oxidase mechanisms, PBO nets could confer additional personal protection., Competing Interests: All the authors declare that they have no competing interests.

Background: Large distribution of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) contributed to a significant decrease in malarial mortality. Unfortunately, large insecticide resistance in malaria vectors occurred and is a threat to the future use of these control approaches. The purpose of this study was to explore a new approach for vector control. Patches containing Bacillus thuringiensis var. israelensis (Bti) solubilized Cry toxins mixed with sugar were developed and tested in the laboratory with pyrethroid-resistant Anopheles gambiae s.l. using tunnel tests., Methods: Mosquitoes were released at 6:00 p.m. into a large tunnel separated by a bed net, perforated with nine holes, from a smaller chamber with a guinea pig. Nine Bti sugar patches (BSPs) were attached to the bed net between the nine holes. Fourteen hours later (8:00 a.m.), mosquitoes were collected from the tunnel and the guinea pig chamber. Live females were kept in cups and were fed a sugar solution (5%) for 72 h and delayed mortality was followed. The results were reported as passing, blood fed and mortality rates., Results: Mosquito populations that are resistant to the insecticides in the bed net, exhibited high mortality (60%) in the presence of the BSPs. Untreated bed nets with patches in the tunnel test killed 66-95% of the mosquitoes that landed and untreated bed nets were superior to treated bed nets., Conclusion: BSPs efficiently kill resistant mosquitoes that land on treated and untreated bed nets and thus could ultimately reduce the number of vector-borne malarial mosquitoes., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Vector control constitutes a fundamental approach in reducing vector density and the efficient option to break malaria transmission in Africa. Malaria vectors developed resistance to almost all classes of insecticides recommended by WHO for vector control in most places of African countries and may compromise the vector control strategies. This study updated the resistance status of Anopheles gambiae complex populations to insecticides recommended for vector control in the western part of Burkina Faso. Insecticide susceptibility bioassays were performed on seven natural populations of An. gambiae complex from western Burkina Faso in the 2016 rainy season using the WHO protocol. Biochemical assays were carried out according to the WHO protocol on the same populations to estimate detoxifying enzymes activities including non-specific esterases (NSEs), oxidases (cytochrome P450) and Glutathione-S-Transferases (GSTs). Polymerase Chain Reactions (PCRs) were performed for the identification of the An. gambiae complex species as well as the detection of kdr-west and ace-1 mutations. Susceptibility bioassays showed that An. gambiae complex was multi-resistant to pyrethroids, DDT and carbamates in almost all areas. The mortality rates ranged from 10 to 38%, 2.67 to 59.57% and 64.38 to 98.02% for Deltamethrin, DDT and Bendiocarb respectively. A full susceptibility (100%) to an organophosphate, the Chlorpyrifos-methyl, was observed at the different sites. Three (3) species of the An. gambiae complex were identified: An. gambiae s.s, An. coluzzii and An. arabiensis. The frequencies of the kdr-w mutation were highly widespread (0.66 to 0.98) among the three species of the complex. The ace-1 mutation was detected at low frequencies (0 to 0.12) in An. gambiae s.s and An. coluzzii. A high level of GSTs and NSEs were observed within the different populations of the An. gambiae complex. Several mechanisms of insecticide resistance were found simultaneously in the same populations of An. gambiae complex conferring high multi-resistance to DDT, Carbamate and Pyrethroids. The full susceptibility of An. gambiae complex to organophosphates is a useful data for the national malaria control program in selecting the most appropriate products to both maintain the effectiveness of vector control strategies and best manage insecticide resistance as well as developing new alternative strategies for the control of major malaria vectors in Burkina Faso., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: A severe outbreak of dengue occurred in Burkina Faso in 2016, with the most cases reported in Ouagadougou, that highlights the necessity to implement vector surveillance system. This study aims to estimate the risk of arboviruses transmission and the insecticide susceptibility status of potential vectors in four sites in Burkina Faso. Methods: From June to September 2016, house-to-house cross sectional entomological surveys were performed in four cities stretching along a southwest-to-northeast railway transect. The household surveys analyzed the presence of Aedes spp. larvae in containers holding water and the World Health Organization (WHO) larval abundance indices were estimated. WHO tube assays was used to evaluate the insecticide susceptibility within Aedes populations from these localities. Results: A total of 31,378 mosquitoes' larvae were collected from 1,330 containers holding water. Aedes spp. was the most abundant (95.19%) followed by Culex spp. (4.75%). Aedes aegypti a key vector of arboviruses (ARBOV) in West Africa was the major Aedes species found (98.60%). The relative larval indices, house index, container and Breteau indexes were high, up to 70, 35, and 10, respectively. Aedes aegypti tended to breed mainly in discarded tires and terracotta jars. Except in Banfora the western city, Ae. aegypti populations were resistant to deltamethrin 0.05% in the other localities with low mortality rate under 20% in Ouagadougou whereas they were fully susceptible to malathion 5% whatever the site. Intermediate resistance was observed in the four sites with mortality rates varying between 78 and 94% with bendiocarb 0.1%. Conclusions: This study provided basic information on entomological indices that can help to monitor the risks of ARBOV epidemics in the main cities along the railway in Burkina Faso. In these cities, all larval indices exceeded the risk level of ARBOV outbreak. Aedes aegypti the main species collected was resistant to deltamethrin 0.05% and bendiocarb 0.1% whereas they were fully susceptible to malathion 5%. The monitoring of insecticide resistance is also important to be integrated to the vector surveillance system in Burkina Faso.

Background: A novel strategy applying an organophosphate-based insecticide paint on doors and windows in combination with long-lasting insecticide-treated nets (LLINs) was tested for the control of pyrethroid-resistant malaria vectors in a village setting in Vallée du Kou, a rice-growing area west of Burkina Faso., Methods: Insecticide Paint Inesfly 5A IGR™, comprised of two organophosphates and an insect growth regulator, was applied to doors and windows and tested in combination with pyrethroid-treated LLINs. The killing effect was monitored for 5 months by early morning collections of anophelines and other culicids. The residual efficacy was evaluated monthly by WHO bioassays using Anopheles gambiae 'Kisumu' and local populations of Anopheles coluzzii resistant to pyrethroids. The spatial mortality efficacy (SME) at distances of 1 m was also assessed against pyrethroid-susceptible and -resistant malaria vectors. The frequency of L1014F kdr and Ace-1 R G119S mutations was, respectively, reported throughout the study. The Insecticide Paint Inesfly 5A IGR had been tested in past studies yielding a long-term mortality rate of 80% over 12 months against An. coluzzii, the local pyrethroid-resistant malaria vector. The purpose of the present study is to test if treating smaller, targeted surfaces (e.g. doors and windows) was also efficient in killing malaria vectors., Results: Treating windows and doors alone yielded a killing efficacy of 100% for 1 month against An. coluzzii resistant to pyrethroids, but efficacy reduced quickly afterwards. Likewise, WHO cone bioassays yielded mortalities of 80-100% for 2 months but declined to 90 and 40% 2 and 3 months after treatment, respectively. Mosquitoes exposed to insecticide paint-treated surfaces at distances of 1 m, yielded mortality rates of about 90-80% against local pyrethroids-resistant An. coluzzii during the first 2 months, but decreased to 30% afterwards. Anopheles coluzzii was reported to be exclusively the local malaria vector and resistant to pyrethroids with high L1014 kdr frequency., Conclusion: The combination of insecticide paint on doors and windows with LLINs yielded high mortality rates in the short term against wild pyrethroid-resistant malaria vector populations. A high SME was observed against laboratory strains of pyrethroid-resistant malaria vectors placed for 30 min at 1 m from the treated/control walls. The application of the insecticide paint on doors and windows led to high but short-lasting mortality rates. The strategy may be an option in a context where low cost, rapid responses need to be implemented in areas where malaria vectors are resistant to pyrethroids.

Novel approaches to area-wide control of vector species offer promise as additional tools in the fight against vectored diseases. Evaluation of transgenic insect strains aimed at field population control in disease-endemic countries may involve international partnerships and should be done in a stepwise approach, starting with studies in containment facilities. The preparations of both new-build and renovated facilities are described, including working with local and national regulations regarding land use, construction, and biosafety requirements, as well as international guidance to fill any gaps in regulation. The examples given are for containment categorization at Arthropod Containment Level 2 for initial facility design, classification of wastes, and precautions during shipping. Specific lessons were derived from preparations to evaluate transgenic (non-gene drive) mosquitoes in West and East African countries. Documented procedures and the use of a non-transgenic training strain for trial shipments and culturing were used to develop competence and confidence among the African facility staff, and along the chain of custody for transport. This practical description is offered to support other research consortia or institutions preparing containment facilities and operating procedures in conditions where research on transgenic insects is at an early stage.

Background: Malaria vectors have acquired widespread resistance throughout sub-Saharan Africa to many of the currently used insecticides. Hence, there is an urgent need to develop alternative strategies including the development of new insecticides for effective management of insecticide resistance. To maintain progress against malaria, it is necessary to identify other residual insecticides for mosquito nets. In the present WHOPES phase II analogue study, the utility of chlorfenapyr, a pyrrole class insecticide mixed with alpha-cypermethrin on a long-lasting mosquito bed net was evaluated against Anopheles gambiae s.l., Methods: Bed nets treated with chlorfenapyr and alpha-cypermethrin and mixture of both compounds were tested for their efficacy on mosquitoes. Washed (20 times) and unwashed of each type of treated nets and were tested according to WHOPES guidelines. Efficacy of nets were expressed in terms of blood-feeding inhibition rate, deterrence, induced exophily and mortality rate. The evaluation was conducted in experimental huts of Vallée du Kou seven (VK7) in Burkina Faso (West Africa) following WHOPES phase II guidelines. In addition, a WHOPES phase I evaluation was also performed., Results: Mixture treated nets killed significantly (P < 0.05) more mosquitoes than solo alpha-cypermethrin nets, unwashed and washed. Proportionally, this equated to mortalities of 78 and 76% (for mixture nets) compared to only 17 and 10% (for solo alpha-cypermethrin) to An. gambiae, respectively. In contrast mixture net proportions were not significantly (P > 0.05) different from nets treated with chlorfenapyr 200 mg/m 2 unwashed (86%). The washed and unwashed nets treated with the mixtures resulted in personal protection against An. gambiae s.l. biting 34 and 44%. In contrast the personal protection observed for washed and unwashed alpha-cypermethrin treated nets generated (14 and 24%), and chlorfenapyr solo treated net was rather low (22%)., Conclusion: Among all nets trialled, the combination of chlorfenapyr and alpha-cypermethrin on bed nets provided better mortality in phase II after 20 washes. Results suggest that this combination could be a potential insecticide resistance management tool for preventing malaria transmission in areas compromised by the spread of pyrethroid resistance.

Many studies have shown the role of agriculture in the selection and spread of resistance of Anopheles gambiae s.l. to insecticides. However, no study has directly demonstrated the presence of insecticides in breeding sources as a source of selection for this resistance. It is in this context that we investigated the presence of pesticide residues in breeding habitats and their formal involvement in vector resistance to insecticides in areas of West Africa with intensive farming. This study was carried out from June to November 2013 in Dano, southwest Burkina Faso in areas of conventional (CC) and biological cotton (BC) growing. Water and sediment samples collected from breeding sites located near BC and CC fields were submitted for chromatographic analysis to research and titrate the residual insecticide content found there. Larvae were also collected in these breeding sites and used in toxicity tests to compare their mortality to those of the susceptible strain, Anopheles gambiae Kisumu. All tested mosquitoes (living and dead) were analyzed by PCR for species identification and characterization of resistance genes. The toxicity analysis of water from breeding sites showed significantly lower mortality rates in breeding site water from biological cotton (WBC) growing sites compared to that from conventional cotton (WCC) sites respective to both An. gambiae Kisumu (WBC: 80.75% vs WCC: 92.75%) and a wild-type strain (49.75% vs 66.5%). The allele frequencies L1014F, L1014S kdr, and G116S ace -1R mutations conferring resistance, respectively, to pyrethroids and carbamates / organophosphates were 0.95, 0.4 and 0.12. Deltamethrin and lambda-cyhalothrin were identified in the water samples taken in October/November from mosquitoes breeding in the CC growing area. The concentrations obtained were respectively 0.0147ug/L and 1.49 ug/L to deltamethrin and lambdacyhalothrin. Our results provided evidence by direct analysis (biological and chromatographic tests) of the role of agriculture as a source of selection pressure on vectors to insecticides used in growing areas.

Twenty years after the latest publications performed on the parasitological indices of malaria transmission in northwest of the second city of Burkina Faso, it was important to update the epidemiological profile of malaria in children under the age of 15 years. The objective of this study was to determine and compare the parasitological parameters of malaria transmission by season, area, and age in the two zones (rice and savanna) in the northwest of Bobo-Dioulasso, Burkina Faso. Overall, the results showed that there was no significant difference in the parasitological indices of malaria transmission within children under fifteen years between the rice site and the savannah site and whatever the season ( P > 0.05). The profound environmental modifications that occurred in the rice zone would have led to changes in vector behavior and consequently to changes in the epidemiological profile of malaria, contrary to the results obtained since the last publications. An entomological study correlated with this study is therefore necessary for effective decision-making for the malaria control in both areas. Future research must now focus on the impact that these profound environmental modifications of rice area are having on malaria control in Burkina Faso., Competing Interests: The authors declare that they have no competing interests.

A pilot study to test the efficacy of combining an organophosphate-based insecticide paint and pyrethroid-treated Long Lasting Insecticide Treated Nets (LLINs) against pyrethroid-resistant malaria vector mosquitoes was performed in a real village setting in Burkina Faso. Paint Inesfly 5A IGR™, comprised of two organophosphates (OPs) and an Insect Growth Regulator (IGR), was tested in combination with pyrethroid-treated LLINs. Efficacy was assessed in terms of mortality for 12 months using Early Morning Collections of malaria vectors and 30-minute WHO bioassays. Resistance to pyrethroids and OPs was assessed by detecting the frequency of L1014F and L1014S kdr mutations and Ace-1(R)G119S mutation, respectively. Blood meal origin was identified using a direct enzyme-linked immunosorbent assay (ELISA). The combination of Inesfly 5A IGR™ and LLINs was effective in killing 99.9-100% of malaria vector populations for 6 months regardless of the dose and volume treated. After 12 months, mortality rates decreased to 69.5-82.2%. The highest mortality rates observed in houses treated with 2 layers of insecticide paint and a larger volume. WHO bioassays supported these results: mortalities were 98.8-100% for 6 months and decreased after 12 months to 81.7-97.0%. Mortality rates in control houses with LLINs were low. Collected malaria vectors consisted exclusively of Anopheles coluzzii and were resistant to pyrethroids, with a L1014 kdr mutation frequency ranging from 60 to 98% through the study. About 58% of An. coluzzii collected inside houses had bloodfed on non-human animals. Combining Inesfly 5A IGR™ and LLINs yielded a one year killing efficacy against An. coluzzii highly resistant to pyrethroids but susceptible to OPs that exhibited an anthropo-zoophilic behaviour in the study area. The results obtained in a real setting supported previous work performed in experimental huts and underscore the need to study the impact that this novel strategy may have on clinical malaria and malaria exposure in children in a similar area of high pyrethroid resistance in South-Western Burkina Faso., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Adult females An. gambiae were exposed in 3 min cone test to treated nets with PPF before or after they were blood fed. The effects of PPF on ovaries development, females oviposition and eggs hatching were assessed. Both unfed and fed mosquitoes exposed to PPF exhibited nearly complete inhibition of fecundity (70-100%) and fertility (90-100%). After females have been exposed once to PPF, the sterilizing effect on their fecundity was observed over 3 consecutive blood meals suggesting that PPF might have an irreversible sterilizing effect. Observation of the ovaries of exposed females to PPF under microscope revealed that the ovaries failed to develop even after several blood meals. The combination of PPF to pyrethroids on bednets could provide better malaria control tool and prevent the further development and spread of pyrethroid resistance in malaria vectors.

An entomological survey was carried out at 15 sites dispersed throughout the three eco-climatic regions of Burkina Faso (West Africa) in order to assess the current distribution and frequency of mutations that confer resistance to insecticides in An. gambiae s.l. populations in the country. Both knockdown (kdr) resistance mutation variants (L1014F and L1014S), that confer resistance to pyrethroid insecticides, were identified concomitant with the ace-1 G119S mutation confirming the presence of multiple resistance mechanisms in the An. gambiae complex in Burkina Faso. Compared to the last survey, the frequency of the L1014F kdr mutation appears to have remained largely stable and relatively high in all species. In contrast, the distribution and frequency of the L1014S mutation has increased significantly in An. gambiae s.l. across much of the country. Furthermore we report, for the first time, the identification of the ace.1 G119S mutation in An. arabiensis populations collected at 8 sites [corrected]. This mutation, which confers resistance to organophosphate and carbamate insecticides, has been reported previously only in the An. gambiae S and M molecular forms. This finding is significant as organophosphates and carbamates are used in indoor residual sprays (IRS) to control malaria vectors as complementary strategies to the use of pyrethroid impregnated bednets. The occurrence of the three target-site resistance mutations in both An. gambiae molecular forms and now An. arabiensis has significant implications for the control of malaria vector populations in Burkina Faso and for resistance management strategies based on the rotation of insecticides with different modes of action.

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 © 2012. Published by Elsevier B.V.)

In the city of Bobo-Dioulasso in Burkina Faso, Anopheles arabiensis has superseded Anopheles gambiae s.s. as the major malaria vector and the larvae are found in highly polluted habitats normally considered unsuitable for Anopheles mosquitoes. Here we show that An. gambiae s.l. adults emerging from a highly polluted site in the city centre (Dioulassoba) have a high prevalence of DDT resistance (percentage mortality after exposure to diagnostic dose=65.8% in the dry season and 70.4% in the rainy season, respectively). An investigation into the mechanisms responsible found an unexpectedly high frequency of the 1014S kdr mutation (allele frequency=0.4), which is found at very low frequencies in An. arabiensis in the surrounding rural areas, and an increase in transcript levels of several detoxification genes, notably from the glutathione transferase and cytochrome P450 gene families. A number of ABC transporter genes were also expressed at elevated levels in the DDT resistant An. arabiensis. Unplanned urbanisation provides numerous breeding grounds for mosquitoes. The finding that Anopheles mosquitoes adapted to these urban breeding sites have a high prevalence of insecticide resistance has important implications for our understanding of the selective forces responsible for the rapid spread of insecticide resistant populations of malaria vectors in Africa.

Malaria control programs are being jeopardized by the spread of insecticide resistance in mosquito vector populations. The situation in Burkina Faso is emblematic with Anopheles gambiae populations showing high levels of resistance to most available compounds. Although the frequency of insecticide target-site mutations including knockdown resistance (kdr) and insensitive acetylcholinesterase (Ace-1(R)) alleles has been regularly monitored in the area, it is not known whether detoxifying enzymes contribute to the diversity of resistance phenotypes observed in the field. Here, we propose an update on the phenotypic diversity of insecticide resistance in An. gambiae populations sampled from 10 sites in Burkina Faso in 2010. Susceptibility to deltamethrin, permethrin, DDT, bendiocarb and fenithrotion was assessed. Test specimens (N = 30 per locality) were identified to species and molecular form and their genotype at the kdr and Ace-1 loci was determined. Detoxifying enzymes activities including non-specific esterases (NSEs), oxydases (cytochrome P450) and Glutathione S-Transferases (GSTs) were measured on single mosquitoes (N = 50) from each test locality and compared with the An. gambiae Kisumu susceptible reference strain. In all sites, mosquitoes demonstrated multiple resistance phenotypes, showing reduced mortality to several insecticidal compounds at the same time, although with considerable site-to-site variation. Both the kdr 1014L and Ace-1(R) 119S resistant alleles were detected in the M and the S forms of An. gambiae, and were found together in specimens of the S form. Variation in detoxifying enzyme activities was observed within and between vector populations. Elevated levels of NSEs and GSTs were widespread, suggesting multiple resistance mechanisms segregate within An. gambiae populations from this country. By documenting the extent and diversity of insecticide resistance phenotypes and the putative combination of their underlying mechanisms in An. gambiae mosquitoes, our work prompts for new alternative strategies to be urgently developed for the control of major malaria vectors in Burkina Faso.