title: Studies on host-seeking, resting behaviour and control of the dengue vector Aedes aegypti.
Creators: name: Abu Hasan, Hadura
Publisher: name: University of Liverpool Repository
Year: 2015

description: Aedes aegypti is the main vector of dengue worldwide. A highly anthropophilic and endophilic mosquito, its behaviour is a major influence on dengue epidemiology and a major challenge to vector control, which is the only dengue prevention method available. A series of studies into host-seeking and resting behaviour were carried out in the laboratory. In Penang, Malaysia, the efficacy of standard and a novel modified form of indoor residual spraying was evaluated in a field trial and the insecticide susceptibility of local vector populations was determined. Arrival patterns of female Ae. aegypti were investigated at a seated human-bait protected by an adhesive-coated net. Mosquitoes preferentially landed on the top and nearest upper vertical surfaces of the net, clustering in a region above the volunteer’s head. Although not previously reported in Ae. aegypti, this behaviour supported the proposition that a plume of potential host attractants rises from the human host. Resting preferences of unfed female Ae. aegypti were investigated using simple two-dimensional panel targets and resting boxes. Exploring the influence of colour, texture, adhesive and target height, the highest resting rates were found on black targets in a vertical configuration at 90 cm above ground. Target texture and adhesive factor did not influence target attractiveness. Data also indicated that female Ae. aegypti were randomly distributed on the panels. In laboratory tests, significantly higher numbers of mosquitoes were captured in resting boxes by raising internal humidity to over 65%. However, a field test in Malaysia did not capture any Aedes sp., although Cx. quinquefasciatus were caught. A randomised-controlled trial was conducted in Penang, Malaysia to investigate the effect of indoor residual spraying (IRS) on Ae. aegypti and Ae. albopictus populations. Two insecticides (lambda-cyhalothrin and pirimiphos-methyl) were delivered either by standard (entire interior surface sprayed) or selective IRS (upper walls and ceilings sprayed) methods. Throughout the three-month study, entomological indices fluctuated considerably and, while there was some evidence of an overall effect throughout the study area, due to a number of confounders comparison between treatments was not possible and the outcome was ultimately inconclusive. At the trial study site in Penang, the insecticide susceptibility status of local populations of Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus were investigated. All were found to be resistant to lambda-cyhalothrin. For pirimiphos-methyl, Ae. aegypti and Ae. albopictus remained susceptible but Cx. quinquefasciatus was classed as ‘suspected resistance’ and potential resistance management strategies are discussed. The study has demonstrated the potential to improve traps or targets for Ae. aegypti by simple alterations to their design. The potential of IRS in the control of dengue vectors remains to be confirmed. The data on emerging insecticide resistance in the mosquito vector populations is timely and provides an evidence base for local authorities to reconsider management strategies that are currently in place for the control of dengue vectors in Malaysia.