Is Malathion Still Effective? A Scoping Review of Insecticide Resistance in Aedes aegypti

Abstract

HistoryAedes aegypti is the primary vector of dengue fever, and control still relies on organophosphate insecticides, particularly malathion.The intensive and repeated use of malathion in vector control programs has raised concerns about the development of resistance in Aedes aegypti populations in endemic areas globally.The main objective was to systematically analyze the susceptibility and resistance status of Aedes aegypti to malathion in various geographical areas, and to identify the underlying resistance mechanisms.The scoping review was conducted following the Arksey and O'Malley framework and the PRISMA-ScR guidelines.We conducted a literature search through PubMed, Scopus, Web of Science, Google Scholar, ScienceDirect, and ProQuest, with no publication year restrictions.Sixteen studies met the inclusion criteria from 885 identified records.Data were synthesized narratively and presented in structured tables.The resistance status of Ae. aegypti to malathion varies significantly across regions.Populations in the Philippines, Nigeria, and parts of Indonesia remain susceptible (mortality ≥ 98 %), whereas populations in Sri Lanka, Brazil, Puerto Rico, and Jamaica show significant resistance (mortality < 90 %).The dominant resistance mechanism is metabolic, involving increased activity of esterase, glutathione Stransferase, and cytochrome P450, with no Ace-1 target-site mutation (G119S) detected.Major contributing factors include prolonged malathion use, a high frequency of household insecticides, lack of insecticide rotation, exposure to agricultural pesticides, and urbanization.The effectiveness of malathion against Ae.aegypti is site-specific.Regular resistance monitoring using standardized bioassays supplemented with molecular surveillance is essential.Insecticide rotation strategies, synergistic use, and integrated vector control approaches are recommended to maintain effective dengue vector control.

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