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sur le développement des zones arides et semi-arides

Titre : The ecology and behaviour of insecticide resistant malaria vectors and implications for control in Burkina Faso

Auteur : Sanou, Antoine

Université de soutenance : University of Glasgow

Grade : Doctor of Philosophy (PhD) 2020

Résumé partiel _ Long-Lasting Insecticide-Treated Nets (LLINs) and Indoor Residual Spraying (IRS) are the most common and successful methods for malaria vector control in Africa. There is growing evidence of shifts in mosquito vector biting and resting behaviours in several African settings where high LLIN coverage has been achieved. These changes, combined with growing insecticide resistance, may reduce intervention success by decreasing the contact between vectors and insecticide-treated surfaces. While insecticide resistance in malaria vectors has been widely investigated, less is known about the implications of mosquito behavioural changes to malaria control. In recent years, LLIN programmes appear to have a reducing impact in a small number of high burden African countries including Burkina Faso. This reducing effectiveness is hypothesized to be the result of insecticide resistance, but the potential additional contribution of mosquito behavioural avoidance strategies has not yet been investigated in Burkina Faso. The aim of this PhD was to investigate the contribution of insecticide resistance and mosquito behaviours to the persistence of malaria transmission in southwestern Burkina Faso following a national LLIN-distribution campaign. Specific objectives were to (i) evaluate the performance of a new mosquito sampling method, the Mosquito Electrocuting Trap (MET) to measure spatial and temporal variation in human exposure to malaria vectors ; and characterize the spatial, seasonal and longer-term trends in (ii) vector ecology and behaviours, (iii) insecticide resistance within Anopheles gambiae sensu lato (s.l.) and (iv) malaria vector survival and transmission potential in rural Burkina Faso. A two-year programme of longitudinal mosquito vector surveillance was initiated within 12 villages of south-western Burkina Faso in 2016, shortly after completion of a mass LLIN distribution. Host seeking malaria vectors were sampled monthly using Human Landing Catches (HLC) and METs conducted inside houses and in the surrounding outdoor area (911 households in total). Resting bucket traps (RBTs) were used to sample indoor and outdoor resting vectors. In an initial study (Chapter 2), I evaluated the performance of the MET relative to the HLC for sampling host-seeking malaria vectors over 15 months in 12 villages. Overall, the MET caught proportionately fewer An. gambiae s.l. than the HLC (mean estimated number of 0.78 versus 1.82 indoors, and 1.05 versus 2.04 outdoors). However provided a consistent representation of vector species composition, seasonal and spatial dynamics, biting behaviour (e.g. location and time) and malaria infection rates relative. The MET slightly underestimated the proportion of bites that could be prevented by LLINs relative to the HLC (5%). However, given the major advantage of the MET of reducing human infection risk during sampling, I conclude these limitations are acceptable and that the MET presents a promising and safer alternative for monitoring human exposure to malaria vectors in outdoor environments.

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