Effectiveness of Pyriproxyfen and Olyset Duo in Controlling Insecticide Resistant Mosquito Populations in Burkina Faso

摘要

The escalation of Long-Lasting Insecticidal Nets (LLINs) mass distribution marked the beginning of a period of malaria decline in sub-Saharan Africa. However, the emergence and spread of insecticide resistance in malaria mosquitoes is a threat to the effectiveness and sustainability of this vector control method. In this context, it is necessary to design and evaluate new compounds and methods that attenuate or even reverse the insecticide resistance trend. Olyset Duo is a novel LLIN that combines the insecticide properties of permethrin and the chemosterilising effect of pyriproxyfen (PPF). The rationale is that resistant mosquitoes that survive the contact with the net would not be able to transfer the resistance genes to the offspring, eventually influencing the resistant phenotype of the mosquito population. In the first part of this study the sterilising and sub-lethal effect of PPF and Olyset Duo was evaluated by a range of bioassays with laboratory and wild mosquito populations. PPF significantly affected the longevity, oogenesis, oviposition and hatching rate of susceptible and resistant mosquitoes, although the effect was partially diminished on the resistant colonies. The possible reasons and implications of PPF performance under controlled conditions are discussed. The second part of this thesis was done within the context of an Olyset Duo Randomised Controlled Trial (RCT) set in Banfora District, Burkina Faso. The RCT had a stepped-wedge design which ensured that Olyset Duo nets gradually replaced Olyset nets in randomly allocated cluster of villages until the Olyset Duo coverage was total. Wild mosquitoes collected in sentinel sites with Olyset Duo showed evident signs of reproductive impairment even after 1 year of deployment. Insecticide resistance strength was monitored during the RCT in several sentinel sites, and time-response data showed an overall reduction of permethrin resistance strength after the distribution of Olyset Duo. This is the most detailed study on the effect of Olyset Duo on key entomological factors of wild mosquito populations. The standardised protocols as well as the dataset obtained are valuable information for ongoing evaluation of Olyset Duo and PPF as a tool for controlling malaria mosquitoes and as a potential alternative for insecticide resistance management.