At present, our understanding of how insecticide resistance impacts the performance of insecticide treated nets (ITNs) is drawn largely from small-scale bioassays that measure the proportion of mosquitoes that are killed following contact.
While useful, this alone does not give a full picture of the ways in which resistance could impact the effectiveness of ITNs. For example, mosquitoes that survive initial contact with insecticides may be unable to transmit malaria in the longer-term. Alternatively, mosquitoes that appear “susceptible” to insecticides may be changing their behaviour to bite outside of homes where they cannot be targeted by ITNs. The full spectrum of what resistance actually consist of, and its impact on ITN performance, requires thorough understanding of the ecology and behaviour of insecticide resistant mosquitoes in natural populations.
Activities in this work package aim to address this knowledge gap through a combination of novel semi-field studies of mosquito fitness and behaviour, detailed surveillance of vector populations, and spatial modeIling of vector ecology and malaria risk. Over 3 years we will conduct detailed surveillance of the species composition, seasonal dynamics and biting behaviours of mosquito vectors from 12 sites in the Cascades region of Burkina Faso where insecticide resistance levels are already high. Using novel sampling methods that allow us to safely record the time and location of mosquito biting, we will assess if and how vector behaviour and transmission potential vary in response to ITN challenge and environmental variation.
Additional experimental studies will quantify how insecticide resistance impacts mosquito fitness and transmission potential. Using a video-tracking system in an experimental hut, we will study the behaviour of mosquitoes as they try to reach their human hosts within ITNs. This system allows us to investigate in detail a wide range of vector feeding behaviours and responses to different types of ITNs, including direct measurement of whether or not these nets will continue to be an effective barrier to resistant mosquitoes.
Finally, we will integrate data from all of these studies into a spatially explicit statistical model of mosquito vector ecology and resistance traits. This model will be used to quantify the relative contribution of mosquito behaviour and insecticide resistance to hotspots of transmission within the study area. In combination, these activities will considerably expand our understanding of the consequences of physiological and behavioural resistance to continued effectiveness of ITN-based control programmes.