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.

The continued absence of an effective and safe tetravalent dengue vaccine and the lack of specific anti-viral treatment have made mosquito vector control using chemical insecticides as the mainstream for dengue prevention and control. However, the long-term use of chemical insecticides may induce resistance. Hence detection of insecticide resistance in dengue vectors is crucially important in ensuring the insecticide-based intervention in dengue control program is still effective and reliable. In this study, the susceptibility status of Aedes aegypti from five selected dengue hotspots in Klang Valley, Malaysia against pyrethroids was determined by employing the World Health Organization (WHO) protocol of adult bioassay. Four types of pyrethroids were tested against adult female Aedes aegypti to determine the knockdown rate, post 24-h adult mortality and resistance ratio. All field-collected Aedes aegypti strains were resistant to the four pyrethroids tested, except for the Taman Sungai Jelok (TSJ) strain. Permethrin exhibited the lowest knockdown rate against Aedes aegypti, followed by deltamethrin, cyfluthrin and lambda-cyhalothrin. This present study indicated the widespread of pyrethroid resistance in Aedes aegypti in Klang Valley, indicating the needs of implementing alternative measures in vector control program. The data in this study can be utilised as an input for insecticide resistance management of Aedes aegypti in Malaysia.

Three genomic regions, VP4 capsid, VP1 capsid and 3D RNA polymerase of human enterovirus 71 (EV-71) and coxsackievirus A16 (CV-A16) were sequenced to understand the evolution of these viruses in Malaysia. A total of 42 EV-71 and 36 CV-A16 isolates from 1997-2008 were sequenced. Despite the presence of many EV-71 subgenotypes worldwide, only subgenotypes B3, B4, B5, C1 and C2 were present in Malaysia. Importation of other subgenotypes such as C3, C4/D and C5 from other countries was infrequent. For CV-A16, the earlier subgenotype B1 was replaced by subgenotypes B2a and the recent B2c. Subgenotype B2a was present throughout the study while B2c only emerged in 2005. No genetic signatures could be attributed to viral virulence suggesting that host factors have a major role in determining the outcome of infection. Only three EV-71 B3 isolates showed non-consistent phylogeny in the 3D RNA polymerase region which indicated occurrence of recombination in EV-71. High genetic diversity was observed in the Malaysian EV-71 but Malaysian CV-A16 showed low genetic diversity in the three genomic regions sequenced. EV-71 showed strong purifying selection, but that occurred to a lesser extent in CV-A16.