Organophosphate and Pyrethroid Resistance Status of Invasive Aedes aegypti (Diptera: Culicidae) from Iran

The growing concerns regarding the recent invasion of Aedes aegypti in Iran and the potential outbreak of dengue fever, chikungunya and Zika viruses in the country highlight the importance of assessing the susceptibility of this vector to different insecticides.

The study assessed the resistance status of Ae. aegypti resistance to insecticides such as deltamethrin, permethrin, malathion, and temephos in Bandar Abbas City, Hormozgan Province, Iran. The research followed WHO standard testing procedures for adult mosquitoes. Adult susceptibility tests were conducted using 1X the discriminating concentrations to determine the frequency and status of insecticide resistance. Additionally, 5X and 10X the discriminating concentration were used to evaluate the intensity of resistance. Larval susceptibility to temephos was tested using concentrations of 156.25, 31.25, 6.25, 1.25, and 0.25 mg/l of temephos.

Adults were resistant to all three tested insecticides at WHO-recommended diagnostic concentrations (DCs). In terms of resistance intensity, Ae. aegypti exhibited low-intensity resistance to malathion and deltamethrin, while resistance to permethrin was high-intensity. Dose-response analysis regarding the susceptibility of larvae to temephos showed LC₅₀, LC_90, and LC₉₉ values of 0.013, 0.065, and 0.238 mg/l, respectively. These values indicate resistance when compared to the WHO diagnostic dose for temephos resistance of 0.012 mg/l.

The results of this study highlight the need for an urgent strategy to manage resistance to insecticides and strengthen the integrated management program of Ae. aegypti. This fact emphasizes the importance of reducing larval sources and promoting research on alternative methods and products.