Abstract
BackgroundAedes aegypti transmits several arboviral diseases of global public health threat such as dengue, zika, and yellow fever. Recently, a series of yellow fever outbreaks have been reported in different parts of the country. Globally, the control of mosquito-borne diseases has relied heavily on insecticides based vector control efforts. Therefore, we assessed the susceptibility status to three different classes of WHO approved insecticides and evaluated the importance of detoxifying enzymes on insecticides resistance in Aedes aegypti collected from Lagos State, Nigeria. Aedes aegypti immature stages were collected from suitable habitats in peri-domestic areas of Alimosho, Kosofe, Badagry, and Ibeju-Lekki Local Government Areas (LGAs) of Lagos State, 2–5 days old glucose-fed adult female mosquitoes were exposed to discriminating doses of DDT, permethrin, bendiocarb, and PBO synergist using WHO standard procedure and kits. Identification was through morphological means only.ResultsResistance to DDT and permethrin was recorded in all the LGAs, suspected resistance to bendiocarb was recorded in Aedes aegypti from Alimosho while full susceptibility was recorded in other LGAs. PBO synergist significantly increases the 24 h mortality of DDT and permethrin-resistant Aedes aegypti in all the LGAs. The activities of both GSTs and cytochrome P450s increase with decreasing mortality for Aedes aegypti, regression value (R2) ranges from 0.8889 to 0.6224 for GSTs and 0.4379 to 0.616 for cytochrome P450s.ConclusionsAedes aegypti population from Lagos State, Nigeria, have developed resistance to DDT and permethrin, the activities of P450s and GST were implicated in DDT and permethrin resistance in this study. Therefore, a need for regular insecticides monitoring and PBO should be incorporated into Aedes aegypti insecticides control strategies to forestall development of resistance to DDT and pyrethriods.
Highlights
Aedes aegypti transmits several arboviral diseases of global public health threat such as dengue, zika, and yellow fever
Aedes aegypti is the main vector of Yellow fever virus, dengue virus (DENV), chikungunya virus (CHIKV), and zika virus (ZIKV); this mosquito has been a source of global public health concern with the increasing prevalence and incessant outbreaks of yellow fever virus, dengue, and zika virus (WHO, 2017)
In Nigeria, there is paucity of information on the susceptibility status of Aedes aegypti to the different classes of neurotoxic insecticides used in public health, as most of mosquito insecticides studies are focused on the malaria vectors
Summary
Aedes aegypti from the four surveyed LGAs showed high level of resistance to DDT and permethrin with 24 h percentage mortality ranging from 20 to 46% and 29 to 70%, respectively. The estimated knockdown time (KDT) for 50% Aedes aegypti to exposed DDT was lowest in Alimosho LGA (91.8 min) and highest in Ibeju-Lekki. LGA (150.1 min), KDT95 was lowest in Alimosho LGA (444min) and highest in Ibeju-Lekki LGA (965.1 min). KDT50 and KDT95 for permethrin was reduced as compared to DDT, ranging from 45 to 113.6 min for KDT50 and 145.5–599.3 min for KDT95 (Table 1). PBO synergist significantly (P < 0.05) reduces the level of resistance of Aedes aegypti to DDT and permethrin in all surveyed locations, likewise the KDT50 and KDT95 for PBO synergized bioassays were lower compared to that of non-synergized
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