Resistance profiling of Aedes aegypti using intensity concentrations enhances the evaluation of insecticide...

The detection of insecticide resistance is pivotal for characterising the phenotypic resistance of field-collected Aedes aegypti populations, enabling the early identification of resistance trends and safeguarding the efficacy of chemical interventions in vector control programmes. Although the World Health Organization (WHO) adult tube test remains the standard screening method, its reliance on binary classifications of susceptibility and resistance limits the ability to compare the magnitude of resistance among different insecticides. To address this limitation, probit analysis was performed on adult mortality data obtained from a field-collected strain exposed to WHO-recommended discriminating and intensity concentrations. LC50 values were subsequently normalised using a concentration ratio (CR) framework, allowing resistance levels to be quantified and compared across insecticides. The relationship between the CR and slope parameters derived from probit analysis enabled the inference of resistance magnitude within field populations. The results demonstrated that pirimiphos-methyl retained high efficacy against the tested populations, whereas substantial intra-population variation in resistance intensity was observed among pyrethroids and malathion. Lambda-cyhalothrin exhibited the highest level of resistance, followed by permethrin and alpha-cypermethrin. These findings highlight the value of data-driven approaches for enhancing the interpretation of insecticide resistance profiles and providing a more comprehensive assessment of resistance status. By utilising mortality data generated from WHO-recommended discriminating and intensity bioassays, resistance can be evaluated beyond the binary outcomes of standard susceptibility tests, thereby supporting more informed decisions on insecticide rotation and resistance management in vector control programmes.