Phenotypic and ace-1–mediated insecticide resistance in Aedes mosquitoes in Enugu North Senatorial Zone, Nigeria

Abstract

Background: Aedes mosquitoes are major vectors of important viral diseases such as Dengue Fever, Yellow Fever, Chikungunya, and Zika Virus Disease, which continue to pose serious public health challenges in many tropical regions largely due to the increasing resistance of mosquito vectors to commonly used insecticides. This study aimed to determine the insecticidal resistance status of Aedes mosquitoes in four surveyed communities within the Enugu North Senatorial Zone.Methodology: Ovitrapping and larval sampling techniques were used to collect Aedes species from the selected communities (Orba, Umuopu, Obinagu, Neke, and Ekwegbe-Ulo). Fifty ovitraps were sited in each community to trap Aedes eggs. The traps were collected after 72 hours, and ribbons containing eggs were air-dried at room temperature and stored until needed. Larvae from hatched eggs were reared into adults. Immature stages of the mosquitoes were also collected from the field. Molecular identification of the mosquitoes was done using conventional PCR techniques. The mosquitoes were tested for susceptibility using the insecticides bendiocarb, deltamethrin, DDT, and pirimiphosmethyl. Data were analyzed using SPSS 21.0. One-way analysis (ANOVA) and Duncan Multiple Range Test (DMRT) were used to determine significant differences in the mean distribution and resistance of mosquitoes to insecticides in the selected communities, with p<0.05 considered statistically significant.Results: The highest susceptibility of the mosquitoes across Orba, Umuopu, Obinagu, Neke, and Ekwegbe-Ulo was recorded for bendiocarb at 98%, 98%, 75%, 95%, and 100%, respectively, while the least was pirimiphos-methyl at 85%, 46%, 25%, 25%, and 100%, respectively. The highest knockdown efficacy was recorded with deltamethrin (p<0.05) compared to other insecticides. Comparably, no significant (p>0.05) difference in the exposed adults with DDT compared to other insecticides. The molecular detection assay implicated the ace-1 resistance gene as one of the major genes responsible for resistance to insecticides in mosquitoes in the area.Conclusion: Aedes mosquitoes from the selected communities showed different responses to the insecticides tested. Bendiocarb was the most effective, while pirimiphos-methyl was the least effective. The detection of the ace-1 gene indicates the presence of insecticide resistance among the mosquito populations. Regular monitoring of insecticide resistance and proper use of insecticides should be encouraged. Integrated mosquito control measures should also be strengthened to improve vector control effectiveness.