Abstract
Susceptibility and PBO synergist bioassays were done using 3–5 days old female Anopheles mosquito collected from Lagos State, Nigeria with WHO test papers DDT (4%), permethrin (0.75%), Bendiocarb (1%) and PBO (4%) according to standard procedures. The activities of cytochrome P450s, glutathione S-transferase and carboxylesterases were determined using biochemical assays. The presence of kdr-w, kdr-e and Ace-1R mutations were examined using molecular assays. Resistance to DDT and permethrin in An gambiae s.s from the four Local Government Areas (LGAs) was recorded while suspected resistance to bendiocarb was recorded in mosquitoes from Alimosho and Kosofe LGAs. PBO synergist reduced the knockdown time and also recorded significantly (P < 0.05) higher 24 hrs percentage mortality compared to non-synergized bioassays. Increased activities of detoxifying enzymes was recorded in wild mosquito compared to the insecticides susceptible laboratory strain and this was significant (P < 0.05) in P450s, esterase α and β. Kdr-w was detected in An. gambiae s.s from all the LGAs, kdr-e (L1014S) was detected in Alimosho, Kosofe and Ibeju-Lekki, while the Ace-1R gene was detected in Alimosho and Kosofe. Results from this study provide evidence for resistance of An. gambiae from Lagos State to multiple classes of neurotoxic insecticides with multiple resistance mechanisms to these insecticides.
Highlights
Malaria remains a major public health problem in sub-Saharan Africa, the World Health Organization (WHO) estimated 219 million cases and 430,000 mortality attributed to malaria globally in 2017 with Nigeria carrying the highest (19%) burden of the estimated death cases[1]
While the estimated knockdown time for 95% (KDT95) of the mosquitoes from Lagos State exposed to permethrin was 3864.9 minutes for Alimosho Local Government Areas (LGAs), 9361 minutes for Ibeju-Lekki LGA, 136.6 minutes for Badagry and 3127.1 minutes for Kosofe LGA (Table 1)
The WHO and sustainable development goals (SDGs) aim to reduce the global malaria prevalence by 90% in the year 2030, the regular monitoring of the limited available malaria control options including the use of insecticides needs to be harnessed strategically
Summary
Malaria remains a major public health problem in sub-Saharan Africa, the World Health Organization (WHO) estimated 219 million cases and 430,000 mortality attributed to malaria globally in 2017 with Nigeria carrying the highest (19%) burden of the estimated death cases[1]. The use of insecticide based vector control measures is vital for the reduction of malaria incidence globally. In Nigeria, Pyrethriods and DDT resistance has been reported in several parts of the country[7,8,9,10,11,12]. Knockdown resistance (L1014F and L1014S) has first been described in Pyrethriods resistance malaria vector[13,14] These mutations have been identified in Pyrethriods and DDT resistance Anopheles in different parts of Africa[10,15,16,17,18,19]. PBO incorporated into LLINs has shown to be more efficacious and effective in controlling malaria vectors, thereby, reducing malaria incidence[26,27,28,29]
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