Baseline data on the bionomics of Aedes aegypti to support dengue control strategies in Burkina Faso

Purpose: In the last two years Burkina Faso has experienced dengue outbreaks resulting in 2,600 cases and 21 deaths in 2016, and 14,944 cases, 30 deaths in 2017. Lack of preparation and of updated information on Aedes populations hinders responses to the first outbreaks of dengue. We carried out a three-month surveillance study to collect baseline data on Aedes populations including characterization of breeding sites, susceptibility to insecticides, and resting and feeding behaviors in urban, periurban and rural localities in or near Ouagadougou the capital city. Methods & Materials: Vacuum aspirators were used to collect indoor and outdoor resting mosquitoes. Potential breeding sites were sampled for immature stages. Mosquitoes were morphologically identified as A. a aegypti, A. a formosus or intermediate. WHO and CDC susceptibility tests were used to assess A. aegypti susceptibility to commonly-used insecticides at the larval and adult stages. PCR detection methods were applied to identify the bloodmeal origin and qPCR to investigate candidate mutations and gene expression that might underlie resistance to insecticides. Results: Morphological identification showed that classical diagnostics did not consistently separate A. aegypti/formosus with many intermediates found. We recorded an increasing density from urban to rural locality consistent with the abundance and productivity of breeding sites. A. aegypti exhibited more outdoor than indoor biting and, although mixed human-animal blood meals were detected, a strong preference for human hosts was evident. Adults exhibited a higher level of resistance to pyrethroids in the urban area, supported by higher frequencies of the 1534C and 1016I target site mutations and an overall elevated expression of candidate P450 detoxification genes. Both adults and larvae remain susceptible to organophosphates. Conclusion: The results provide baseline data on A. aegypti bionomics in Ouagadougou and its neighborhood that can be used to support the response to outbreaks of dengue and other A. aegypti-transmitted arboviruses in Burkina Faso. The results provide an updated evidence base, essential to establish a locally-informed strategy for vector control.