Insecticide resistance and malaria transmission indicators in Anopheles gambiae s.l. in Bobo-Dioulasso: Implications for vector control strategies
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Background In the context of intensified malaria control efforts in Burkina Faso, this study assessed i) the insecticide resistance status of Anopheles gambiae sensu lato and ii) key entomological indicators of malaria transmission in Bobo-Dioulasso. Methods World Health Organization-standard susceptibility bioassays were conducted on Anopheles populations collected from six neighborhoods (Kua, Sarfalao, Sabaribougou, Dogona, Farakan and Kodeni) testing six insecticides organochlorines (dichlorodiphenyltrichloroethane 4%), organophosphates (pirimiphos-methyl 1.25%), pyrethroids (permethrin 0.75%, deltamethrin 0.05%, alpha-cypermethrin 0.05%), and carbamates (bendiocarb 0.1%). Synergist bioassays using piperonyl butoxide were also performed to investigate metabolic resistance mechanisms, and Plasmodium infection rates were determined via Polymerase Chain Reaction. Results Overall, data revealed high resistance levels to dichlorodiphényltrichloroéthane and pyrethroids, associated with either moderate or higher knockdown resistance mutations (L995F and L995S) allelic frequencies. Fortunately, a susceptibility to bendiocarb and pirimiphos-methyl was found in majority of localities. Restoration of pyrethroid susceptibility following piperonyl butoxide pre-exposure suggests the likely involvement of metabolic resistance mechanisms. Analysis of 622 specimens from the Anopheles gambiae complex revealed a predominance of An. arabiensis (90.8%), followed by An. gambiae s.s. and An. coluzzii . Sporozoite infection rates varied by species, reaching 45.0% in An. coluzzii , 27.4% in An. arabiensis , and 16.2% in An. gambiae s.s. . The overall entomological inoculation rate (EIR) was estimated at 10.624 infectious bites per person, with An. arabiensis contributing the majority (91.2%), underscoring its central role in malaria transmission in Bobo-Dioulasso. Conclusions Despite insecticide resistance, Anopheles populations exhibited high Plasmodium infection rates, highlighting ongoing transmission. These findings emphasize the urgent need for sustained entomological surveillance and resistance management to guide and optimize insecticide-based malaria control strategies.
