Evaluation of diagnostic doses and susceptibility status against pyrethroids in Aedes aegypti from Jaipur, Rajasthan: a growing threat to dengue vector control

Background & objectives: The Rajasthan state is one of the arid and semi-arid regions of India, characterized by extreme climatic conditions. In recent years, rising temperatures and altered rainfall patterns have created favourable conditions for the proliferation of mosquito vectors and contribute to the upsurge and sustained transmission of mosquito-borne diseases. The vector control largely depends on chemical insecticides, but their prolonged use can hinder effectiveness due to the emergence of resistance. Therefore, the present study aimed to assess the efficacy of pyrethroids and resistance status in Aedes aegypti populations of Jaipur, Rajasthan. Methods: Adults and larvae of Ae. aegypti were collected from nine localities across Jaipur. Diagnostic doses and adult susceptibility for field-collected (F 0 ) and laboratory-reared (F 5 ) strains of Ae. aegypti were evaluated according to WHO and CDC protocols. Results: Diagnostic doses for deltamethrin, permethrin, and lambda-cyhalothrin were determined 0.005 μg/ml, 0.01 μg/ml, and 0.05 μg/ml, respectively. Aedes mosquitoes showed 100% mortality against all determined diagnostic doses. Lethal concentrations (μg/ml) values indicated a clear susceptibility hierarchy, with deltamethrin showed the highest effectiveness (0.000152-0.000169), followed by lambda-cyhalothrin (0.00066-0.00070) and permethrin (0.00133-0.00155). However, Sanganer (3.66-4.32), Shastri Nagar (3.67-4.52) and Shyam Nagar (3.8-4.52) exhibited the higher levels of resistance ratios against tested pyrethroids. Interpretation & conclusion: Pyrethroids are still effective in vector management, although some locations were observed emerging resistance. It highlights the necessity of continuous monitoring of insecticide resistance patterns in Aedes populations to ensure the long-term success of vector control programs.