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Kudom, Andreas (2015): Insecticide resistance status of Culex species in urban areas in Ghana and efficacy of long lasting nets against them. Dissertation, LMU München: Faculty of Medicine



Background Current strategic plans for malaria control in Ghana include the attainment of 80% of the general population sleeping under insecticide treated materials (ITM) by 2015. This coverage may not be attained if there is non-compliance in the use of bed nets. Failure of ITM to protect users from nuisance mosquitoes, particularly Culex mosquitoes has been cited as one of the major threats to the sustained use of ITM. A nationwide survey was therefore carried out to determine insecticide resistance status of Culex species and efficacy of ITM against them. Methods and materials Mosquito larvae were sampled from various land use and ecological settings and at different seasons. These were reared to adults and used for the various tests. In adults, insecticide susceptibility tests to eight insecticides as well as cone and tunnel bioassays were performed. Biochemical and molecular analyses were also conducted to determine the resistance mechanisms in the study populations. Results Culex quinquefasciatus and C. decens were the Culex species that were identified in the study area. DDT and deltamethrin resistances were evident across the country. A strong relationship between resistance status and urban size was observed in the study population (Pearson χ2 =48.2; df = 1; P<0.0001). Not only kdr and ace1 mutations but also elevated levels of three detoxifying enzymes were found in the study populations. New ITMs evaluated had reduced efficacy against pyrethroid-resistant Culex mosquitoes. Conclusions Insecticide resistance status of Culex species in urban areas of Ghana was determined. Insecticide resistance levels were high in large urban areas. Urbanization and its associated problems as well as ecology and different land use were observed to have some impact on level of insecticide resistance in the Culex population. ITM with synergist and organophosphate insecticides were seen as a possible resistance management tool against pyrethroid-resistant Culex mosquitoes.