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Arboviral diseases such as dengue, Zika and chikungunya transmitted by Aedes mosquitoes have been reported in 34 African countries. Available data indicate that in recent years there have been dengue and chikungunya outbreaks in the West Africa subregion, in countries including Côte d'Ivoire, Burkina Faso, Gabon, Senegal, and Benin. These viral diseases are causing an increased public health burden, which impedes poverty reduction and sustainable development. Aedes surveillance and control capacity, which are key to reducing the prevalence of arboviral infections, need to be strengthened in West Africa, to provide information essential for the formulation of effective vector control strategies and the prediction of arboviral disease outbreaks. In line with these objectives, the West African Aedes Surveillance Network (WAASuN) was created in 2017 at a meeting held in Sierra Leone comprising African scientists working on Aedes mosquitoes. This manuscript describes the proceedings and discusses key highlights of the meeting. [ABSTRACT FROM AUTHOR]

Here, we report the first population genetic study to examine the impact of indoor residual spraying (IRS) on Plasmodium falciparum in humans. This study was conducted in an area of high seasonal malaria transmission in Bongo District, Ghana. IRS was implemented during the dry season (November–May) in three consecutive years between 2013 and 2015 to reduce transmission and attempt to bottleneck the parasite population in humans towards lower diversity with greater linkage disequilibrium. The study was done against a background of widespread use of long‐lasting insecticidal nets, typical for contemporary malaria control in West Africa. Microsatellite genotyping with 10 loci was used to construct 392 P. falciparum multilocus infection haplotypes collected from two age‐stratified cross‐sectional surveys at the end of the wet seasons pre‐ and post‐IRS. Three‐rounds of IRS, under operational conditions, led to a >90% reduction in transmission intensity and a 35.7% reduction in the P. falciparum prevalence (p <.001). Despite these declines, population genetic analysis of the infection haplotypes revealed no dramatic changes with only a slight, but significant increase in genetic diversity (He: pre‐IRS = 0.79 vs. post‐IRS = 0.81, p =.048). Reduced relatedness of the parasite population (p <.001) was observed post‐IRS, probably due to decreased opportunities for outcrossing. Spatiotemporal genetic differentiation between the pre‐ and post‐IRS surveys (D = 0.0329 [95% CI: 0.0209 – 0.0473], p =.034) was identified. These data provide a genetic explanation for the resilience of P. falciparum to short‐term IRS programmes in high‐transmission settings in sub‐Saharan Africa. [ABSTRACT FROM AUTHOR]

• Recent outbreaks of Zika, dengue, and chikungunya have occurred in West Africa • Recently introduced Aedes albopictus is implicated in multiple arbovirus outbreaks • Arbovirus outbreaks have occurred in major urban centers in West Africa • Diverse factors play a role in the emergence of Aedes- borne disease in West Africa • There is urgent need for improved disease surveillance and diagnostic capacity Arboviruses transmitted by Aedes mosquitoes are a growing global concern; however, there remain large gaps in surveillance of both arboviruses and their vectors in West Africa. We reviewed over 50 years of data including outbreak reports, peer-reviewed literature, and prior data compilations describing Zika, dengue, and chikungunya, and their vectors in West Africa. Large outbreaks of dengue, Zika, and chikungunya have recently occurred in the region with over 27,000 cases of Aedes -borne disease documented since 2007. Recent arboviral outbreaks have become more concentrated in urban areas, and Aedes albopictus , recently documented in the region, has emerged as an important vector in several areas. Seroprevalence surveys suggest reported cases are a gross underestimate of the underlying arboviral disease burden. These findings indicate a shifting epidemiology of arboviral disease in West Africa and highlight a need for increased research and implementation of vector and disease control. Rapid urbanization and climate change may further alter disease patterns, underscoring the need for improved diagnostic capacity, and vector and disease surveillance to address this evolving health challenge. Aedes-borne disease occurrence in West Africa. Arboviral disease occurrences were extracted from previous compilations, systematic review of literature, and outbreak reports. Data are organized by timing of outbreak with panels showing oldest (bottom panel) to most recent (top panel) observations Image, graphical abstract. [ABSTRACT FROM AUTHOR]