Bionomics of Aedes aegypti during the 2016-2017 dengue outbreaks in Ouagadougou, Burkina Faso

Abstract

AbstractBackgroundDengue’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 outbreak was centered.MethodologyIn urban, peri-urban and 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.ResultsFrom samples in 1,791 houses, Ae. aegypti was the most abundant mosquito in the two urban localities where it occurred in 46% of containers sampled and comprised over 85% of collections. Results 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 autocorrelation of densities, with partial overlap in adult and immature stage hotspots.ConclusionResults 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 insecticide-based interventions is indicated. The prospects of developing a regional approach to arbovirus control in west Africa or across Africa was discussedAuthor SummaryAedes aegypti is the most efficient vector of human diseases including yellow fever, dengue chikungunya and Zika. West Africa is an emerging hotspot for dengue, as illustrated by Burkina Faso’s outbreaks in 2016 and 2017. Coincidentally, this study investigated the bionomics and behavior of Ae. aegypti in urban, peri-urban and rural localities of Ouagadougou, from August to October in each year. The results from over 1700 homes showed that Ae. aegypti preferentially fed on humans and rested primarily outdoors. The most common pupal productive habitats were discarded vehicle tires, animal water troughs and large water barrels. Infestation rates were higher in the urban and peri-urban localities. A range of community-based control measures are suitable for consideration in a vector control program to prevent outbreaks. Further work is required but the study provides the most complete contemporary description of an Ae. aegypti population in West Africa and provides sufficient evidence to develop programs for prevention and control of outbreaks. The potential of a regional based vector control program for west Africa is discussed briefly.