Vector control for Aedes aegypti and Aedes albopictus mosquitoes implemented in the field in sub-Saharan Africa: a scoping review

BACKGROUND:
Aedes-borne diseases are increasingly reported in sub-Saharan Africa (SSA), where evidence on Aedes control remains scarce. This study reviews Aedes vector control (VC) interventions evaluated in field settings in SSA, to aid future VC strategies.
METHODOLOGY:
Literature was searched via PubMed and ISI Web of Knowledge, using a broad search strategy based on Aedes species and SSA countries. Two reviewers independently screened all records by title/abstract and full text. The evidence was described, discerning between integrated VC strategies during outbreaks and single interventions in non-outbreak settings. A critical assessment of the quality of evidence was provided.
PRINCIPAL FINDINGS:
We included 8 studies evaluating 7 interventions (2 studies referred to the same intervention). The studies were heterogeneous in study design, VC methods, and outcome measurement. Four studies were from West Africa. The studies reported on integrated (2/8) and single (6/8) interventions, including three cluster randomized controlled trials. Non-chemical methods targeting immature stages were frequently reported (5/7), followed by chemical methods against adult (4/7) and immature stages (2/7). Community-based environmental management for source reduction (4/7) showed improved knowledge, but did not lead to a change in practical behavior and/or reduction in entomological indices. Chemical methods were reported to have a temporary impact on entomological indices. Most studies (7/8) used entomological indices, only one in combination with epidemiological outcomes. The assessment of quality of evidence revealed some shortcomings in study designs and issues related to epidemiological outcomes, post-intervention follow-up duration, entomological sampling procedures.
CONCLUSIONS:
Compared with Latin America and Asia, the studies evaluating Aedes VC interventions in SSA are limited. A temporary impact of chemical interventions was reported on entomological parameters, but evidence for reduced transmission was lacking. Environmental management strategies involving communities deserve further study, particularly when integrated with other VC measures tailored to vector bionomics.

Author summary
To date, solid evidence on the effectiveness of vector control methods against Aedes mosquitoes is scarce, with most research coming from Latin America and Asia, although arboviruses are known to circulate in sub-Saharan Africa as well. Our scoping review aims to describe the interventions against Aedes mosquitoes implemented to date in sub-Saharan Africa and their field-tested effectiveness, highlighting the strengths and limitations of available research to provide insights for improving future vector control strategies. We found that the literature in this field is limited and heterogeneous, thus leaving a critical knowledge gap on effectiveness of Aedes vector control interventions in sub-Saharan African countries. Although data are scarce and study design are variable, chemical interventions, applied alone or as part of integrated vector control strategies, have demonstrated some benefits. However, these effects have been short-term and subject to failure if not tailored to how the Aedes mosquito behaves in a specific environment. Community-based interventions aimed at reducing mosquito breeding sources have been investigated in sub-Saharan Africa, but lack sufficient community perception analysis and process evaluation to assess their full impact.