Evaluating the mosquitocidal potential of the isoxazoline sarolaner against the yellow fever mosquito, <i>Aedes aegypti</i> (Diptera: Culicidae)

Aedes aegypti Linnaeus 1762 (Diptera: Culicidae) is the primary vector of several pathogens of public health significance. Insecticide-based preventative measures are a key component of vector-borne disease control programmes. However, widespread insecticide resistance threatens the effectiveness of current control strategies. Sarolaner, an isoxazoline insecticide, offers a novel mode of action and is primarily used for controlling ticks, fleas and mites in companion animals. This study evaluates the insecticidal efficacy of sarolaner against both laboratory-susceptible and resistant strains of Ae. aegypti through various exposure routes. In topical assays, sarolaner outperformed permethrin by >8-fold and >21-fold greater efficacy against resistant strains at 24 and 72 h, respectively. Conversely, it underperformed in susceptible strains by over 8-fold and 2-fold at the same time points. In larval assays, sarolaner exhibited >300-fold greater toxicity than spinosad at 24 and 48 h for both susceptible and resistant strains. Blood-feeding assays showed sarolaner was more toxic than ivermectin by over 17-fold and 10-fold in susceptible and resistant strains, respectively, up to 120 h. While sarolaner was less toxic than dinotefuran in resistant strains through sugar feeding, it was over 3-fold more toxic in susceptible strains. Notably, no cross-resistance was detected with dinotefuran or ivermectin through oral, sugar or blood-feeding applications, though slight cross-resistance was observed with permethrin and spinosad. This study highlights sarolaner's potential as an effective adulticide and larvicide against Ae. aegypti, supporting its further evaluation as a candidate for new chemical formulations.