First comprehensive analysis of Aedes aegypti bionomics during an arbovirus outbreak in west Africa: Dengue in Ouagadougou, Burkina Faso, 2016-2017

Background Dengue's emergence in West Africa was typified by the Burkina Faso outbreaks in 2016 and 2017, the nation's largest to date. In both years, we undertook three-month surveys of Aedes populations in or near the capital city Ouagadougou, where the outbreaks were centered. Methodology In 1200LG (urban), Tabtenga (peri-urban) and Goundry (rural) localities, we collected indoor and outdoor resting mosquito adults, characterized larval habitats and containers producing pupae and reared immature stages to adulthood in the laboratory for identification. All mosquito adults were identified morphologically. Host species (from which bloodmeals were taken) were identified by PCR. Generalized mixed models were used to investigate relationships between adult or larval densities and multiple explanatory variables. Results From samples in 1,780 houses, adult Ae. aegypti were significantly more abundant in the two urban localities (Tabtenga and 1200 LG) in both years than in the rural site (Goundry), where Anopheles spp. were far more common. Results from adult collections indicated a highly exophilic and anthropophilic (> 90% bloodmeals of human origin) vector population, but with a relatively high proportion of bloodfed females caught inside houses. Habitats producing most pupae were waste tires (37% of total pupae), animal troughs (44%) and large water barrels (30%). While Stegomyia indices were not reliable indicators of adult mosquito abundance, shared influences on adult and immature stage densities included rainfall and container water level, collection month and container type/purpose. Spatial analysis showed auto-correlation of densities, with a partial overlap in adult and immature stage hotspots. Conclusion Results provide an evidence base for the selection of appropriate vector control methods to minimize the risk, frequency and magnitude of future outbreaks in Ouagadougou. An integrated strategy combining community-driven practices, waste disposal and insecticidebased interventions is proposed. The prospects for developing a regional approach to arbovirus control in West Africa or across Africa are discussed.

Automated summary

The emergence of dengue in West Africa, particularly the outbreaks in Burkina Faso in 2016 and 2017, has led to surveys of Aedes populations in the capital city of Ouagadougou. The results show that the abundance of adult Ae. aegypti is significantly higher in urban areas compared to the rural site, which has a higher population of Anopheles spp. The vector population is highly anthropophilic and exhibits a high proportion of bloodfed females caught inside houses. The primary larval habitats are waste tires, animal troughs, and large water barrels. Factors influencing adult and immature stage densities include rainfall, container water level, collection month, and container type/purpose.