The need for new vector control approaches targeting outdoor biting anopheline malaria vector communities

Abstract

Since the implementation of Roll Back Malaria, the widespread use of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) is thought to have played a major part in the decrease in mortality and morbidity achieved in malaria-endemic regions. In the past decade, resistance to major classes of insecticides recommended for public health has spread across many malaria vector populations. Increasingly, malaria vectors are also showing changes in vector behaviour in response to current indoor chemical vector control interventions. Changes in the time of biting and proportion of indoor biting of major vectors, as well as changes in the species composition of mosquito communities threaten the progress made to control malaria transmission. Outdoor biting mosquito populations contribute to malaria transmission in many parts of sub-Saharan Africa and pose new challenges as they cannot be reliably monitored or controlled using conventional tools. Here, we review existing and novel approaches that may be used to target outdoor communities of malaria vectors. We conclude that scalable tools designed specifically for the control and monitoring of outdoor biting and resting malaria vectors with increasingly complex and dynamic responses to intensifying malaria control interventions are urgently needed. These are crucial for integrated vector management programmes designed to challenge current and future vector populations.

Geographically extensive larval surveys reveal an unexpected scarcity of primary vector mosquitoes in a region of persistent malaria transmission in western Zambia

“…When viewed in light of the high level of residual transmission in the study area, our results highlight the potential need for alternative interventions that are effective against outdoor-biting vectors [8,77].…”

“…Larviciding targets mosquitoes when they are con ned to aquatic habitats, irrespective of future adult feeding and resting behaviours; this not only avoids behavioural resistance, but also circumvents increasing resistance to insecticides used in ITNs and IRS, which is a global concern [8,64,74,78,79,80,81]. Modelling and other analyses suggest that larviciding is more effective if targeted [81,82,83,84], notwithstanding that it is untargeted, blanket applications of larval source management that have been historically successful (e.g.…”

Nextgen Vector Surveillance Tools: Sensitive, Specific, Cost-effective and Epidemiologically Relevant

“…More e cient sampling methods which are less dependent on human resources and less expensive will facilitate increased surveillance (both frequency of sampling and number of sampling locations). Vector surveillance is fundamental to deploying more effective vector control [42], in particular targeting vectors outdoors [6], which requires an understanding of mosquito behaviours, particularly outdoor movements, resting behaviours and larval habitats [43]. Surveillance data needs to be epidemiologically relevant to be used directly in models to guide programmatic choices on interventions and combinations of interventions deployed.…”

“…These methods may lack the sensitivity to detect subtle changes in vector behaviours or may not directly measure the vector behaviours that new vector control tools may impact (e.g., repellency, sugar feeding, mating) [6,7].…”

“…Algorithms are needed to correlate vector insecticide resistance bioassay and genetic data to intervention impact and to correlate hut data to intervention e cacy at scale.DiscussionSurveillance encompasses the eld sampling tools, their deployment strategies and the laboratory techniques to analyze captured vectors. Vector surveillance provides critical data for decision-making to ensure that malaria control programs remain effective and responsive to threats such as insecticide resistance, behavioural resistance, changes in species composition and invasive species[2,6,7,[36][37][38][39].…”