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The response to recent dengue outbreaks in Burkina Faso was insecticide-based, despite poor knowledge of the vector population's susceptibility to the insecticides used. Here, we report on the susceptibility to the main insecticide classes and identify important underlying mechanisms in Aedes aegypti populations in Ouagadougou and Banfora, in 2019 and 2020. Wild Ae. aegypti were tested as adults in WHO bioassays and then screened in real time melting curve qPCR analyses to genotype the F1534C, V1016I, and V410L Aedes kdr mutations. Ae. aegypti showed moderate resistance to 0.1% bendiocarb (80-95% survival post-exposure), 0.8% Malathion (60-100%), 0.21% pirimiphos-methyl (75% - 97%), and high resistance to 0.03% deltamethrin (20-70%). PBO pre-exposure partially restored pyrethroid susceptibility. Genotyping detected high frequency of 1534C allele (0.92) and moderate 1016I (0.1-0.32). The V410L mutation was detected in Burkina Faso for the first time (frequency 0.1-0.36). Mosquitoes surviving 4 h exposure to 0.03% deltamethrin had significantly higher frequencies of the F1534C mutation than dead mosquitoes (0.70 vs. 0.96, p 0.0001) and mosquitoes surviving 2 - 4 h exposure had a significantly reduced life span. Ae. aegypti from Burkina Faso are resistant to multiple insecticide classes with multiple mechanisms involved, demonstrating the essential role of insecticide resistance monitoring within national dengue control programmes.

Background: Malaria remains a major public health threat in Burkina Faso. In most sub-Saharan African countries, malaria control relies mainly on long-lasting insecticide-treated nets (LLINs) and indoor residual spray (IRS). In Burkina Faso, long-term selection pressure exerted on malaria vectors by insecticide used in agriculture, has been exacerbated by countrywide LLINs distribution campaigns conducted every three years since 2010. The current study investigated insecticide resistance and the mechanisms involved in the malaria vector populations of the Anopheles gambiae complex in urban localities of Ouagadougou, Burkina Faso. Methods: Anopheles gambiae s. l. larvae were collected from three localities of Ouagadougou from July to September 2018, and reared in the laboratory to adults. The susceptibility profile to pyrethroid, carbamate, and organophosphate insecticides was assessed using World Health Organization (WHO) tube assays. PCR was used for mosquito species identification and to detect insecticide target-site mutations involved in insecticide resistance. Results: More than 95% of the collected An. gambiae s. l. were identified as An. arabiensis. WHO susceptibility assays revealed that, in all localities, An. arabiensis displayed high resistance to permethrin and deltamethrin (mortalities both kdr mutations 1014F (0.81) and 1014S (0.18) were recorded, although carbamate and organophosphate-associated Ace-1 119S mutation was not found. Conclusion: High pyrethroid resistance, underpinned, at least in part by high-frequency knockdown resistance mutations, in the urban malaria vector population suggests the potentially poor performance of pyrethroid-only LLINs in the cities where they are distributed. This result supported the switch to next generation LLINs, which are not solely reliant on pyrethroids to kill host-seeking mosquitoes in the cities of Burkina Faso.

Background In rural Burkina Faso, the primary malaria vector Anopheles gambiae sensu lato (s.l.) primarily feeds indoors at night. Identification of factors which influence mosquito house entry could lead to development of novel malaria vector control interventions. A study was therefore carried out to identify risk factors associated with house entry of An. gambiae s.l. in south-west Burkina Faso, an area of high insecticide resistance. Methods Mosquitoes were sampled monthly during the malaria transmission season using CDC light traps in 252 houses from 10 villages, each house sleeping at least one child aged five to 15 years old. Potential risk factors for house entry of An. gambiae s.l. were measured, including socio-economic status, caregiver’s education and occupation, number of people sleeping in the same part of the house as the child, use of anti-mosquito measures, house construction and fittings, proximity of anopheline aquatic habitats and presence of animals near the house. Mosquito counts were compared using a generalized linear mixed-effect model with negative binomial and log link function, adjusting for repeated collections. Results 20,929 mosquitoes were caught, of which 16,270 (77.7%) were An. gambiae s.l. Of the 6691 An. gambiae s.l. identified to species, 4101 (61.3%) were An. gambiae sensu stricto and 2590 (38.7%) Anopheles coluzzii. Having a metal-roof on the child’s sleeping space (IRR = 0.55, 95% CI 0.32–0.95, p = 0.03) was associated with fewer malaria vectors inside the home. Conclusion This study demonstrated that the rate of An. gambiae s.l. was 45% lower in sleeping spaces with a metal roof, compared to those with thatch roofs. Improvements in house construction, including installation of metal roofs, should be considered in endemic areas of Africa to reduce the burden of malaria.