Push-pull tactics to disrupt the host-seeking behaviour of malaria mosquitoes

Malaria remains a major health burden, especially in sub-Saharan Africa. The efficacy of the main vector control tools, insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS), is compromised by the development of physiological and behavioural resistance in the target mosquito species and by changes in the species composition of vector populations. These developments underline the need to develop novel vector control approaches which are complementary to insecticide-based methods. In this thesis, the potential of push-pull tactics as a tool to reduce malaria transmission is explored. It is described how the push-pull concept, originally designed for agricultural pest control, may be translated in a system that targets Anopheles mosquitoes. Several novel repellents are identified in the laboratory and a prototype push-pull system is tested in a semi-field setup. The system is improved and evaluated in a malaria endemic field setting and the push-pull approach is compared and combined with the existing practise of eave screening. Based on the experimental results it is concluded that (1) it is possible to reduce house entry of malaria and other mosquitoes using (spatial) repellents and/or attractant-baited traps; (2) the effect of repellents on house entry is larger and more consistent than the effect of attractant-baited traps; (3) the main function of the attractant-baited traps is to deplete mosquito populations through removal trapping; (4) the attractive and repellent components of the push-pull system complement each other and there is no or very little interaction between them; (5) a push-pull system based on repellent and attractive volatiles can be expected to reduce malaria transmission through a strong decrease of the entomological inoculation rate; (6) eave screening is a highly efficient method to reduce house entry of malaria and other mosquitoes and increases outdoor trap catches, while there is little added value in impregnating screening material with a repellent. In the last chapter, the issue of selection for insensitivity to the used compounds is discussed, as well as methods how to manage it. Furthermore, it is described how the principles of behavioural disruption on which push-pull tactics are based make the technique potentially suitable to target a wider selection of arthropod vectors of disease than malaria mosquitoes alone. It is concluded that future vector control strategies will probably consist of the integration of many different approaches, of which push-pull tactics may be one. By integrating different approaches, it will be possible mitigate the development of resistance while targeting vectors in different life stages, uncompromised by changing behavioural patterns and changes in the composition of vector populations. This would require an integrated view on vector control, knowledge on the ecology of vectors and the political will to invest in programmes that focus on long term sustainable control.