Spatio-temporal trends of insecticide resistance in Indian malaria vectors (2000–2024): a systematic review and meta-analysis

Insecticide resistance in malaria vectors poses a significant threat to the effectiveness of current vector control strategies. The prolonged use of insecticides in Long Lasting Insecticidal Nets (LLIN), Insecticide Treated Nets (ITNs), and Indoor Residual Spraying (IRS) has led to the emergence of resistance among Anopheles mosquito population. This study aims to evaluate the spatial and temporal insecticide resistance trends against dichloro-diphenyl-trichloroethane (DDT), malathion, and deltamethrin among the malaria vectors prevalent in India. Methods A systematic search was conducted in PubMed, Web of Science, and Scopus using Medical Subject Heading (MeSH) terms and keywords. The studies meeting the predefined eligibility criteria, reporting state or district-level insecticide resistance, and published from the year 2000 to 2024 were included for systematic review and meta-analysis. Results A total of 51 studies selected according to the predefined eligibility criteria were included. The results of the meta-analysis highlighted the prevalence of resistance to DDT in almost all Indian states, with the north-eastern region being an exception. Anopheles culicifacies showed very low susceptibility to DDT, whereas Anopheles stephensi, and Anopheles fluviatilis displayed moderate resistance, with notable regional variation. Resistance to Deltamethrin was majorly noticed in Chhattisgarh and Madhya Pradesh with an average percent mortality of 89% (95% CI: 79% − 94%) reported in Anopheles culicifacies, 93% (95% CI: 78% − 98%) in Anopheles stephensi, and 100% (95% CI: 99% − 100%) in Anopheles fluviatialis. Anopheles culicifacies displayed resistance to deltamethrin in some regions, while Anopheles stephensi and Anopheles fluviatilis were highly susceptible to deltamethrin with notable regional variations. Anopheles culicifacies and Anopheles stephensi were highly resistant against Malathion, while Anopheles fluviatialis displayed complete susceptibility. While Anopheles. sundaicus, Anopheles minimus, and Anopheles baimaii were found to be susceptible to all three insecticides. Conclusion Resistance to DDT and Malathion was particularly pronounced across India, whereas Deltamethrin was mostly resistant in the central states. Malaria vectors in the north-eastern states generally remained susceptible, suggesting opportunities for targeted intervention. This study underscores the need for continuous surveillance and monitoring of vector population, disease prevalence, and utilization of personal protection vector management tools like LLIN.