99 - Evaluating the mosquitocidal toxicity of sarolaner against the key disease vector Aedes aegypti.

Abstract: Aedes aegypti is the primary vector of several pathogens of public health significance. Insecticide-based preventative measures are a key component of vector borne-disease control programs. However, the continual spread of insecticide resistance threatens to undermine the integrity of current control efforts. Sarolaner, an isoxazoline class insecticide, is a relatively newer toxicant currently available as tick, flea, and mite control for companion animals. We assessed the insecticidal efficacy of sarolaner against a laboratory susceptible and resistant strain of Ae. aegypti through different routes of exposure. In topical assays, sarolaner outperformed permethrin by >8-fold at 24h and >21-fold at 72h in the resistant strain. However, there was a >8-fold and >2-fold underperformance at 24 and 72h, respectively, in the susceptible strain. Larval application to susceptible and resistant strains revealed sarolaner was >300-fold as toxic as spinosad at both 24 and 48h. Through blood-feeding, sarolaner was more toxic than ivermectin by >17- and >10-fold in Ae. aegypti susceptible and resistant strains, respectively, all the way up to 120h. Sarolaner applied through sugar feeding was less toxic than dinotefuran in the resistant Ae. aegypti strain by 2-fold but >3-fold more toxic in the susceptible strain. Sarolaner was found to be more toxic than fluralaner in larval assays and oral sugar-feeding and blood-feeding assay but had similar levels of toxicity in adult topical application. No cross-resistance was detected via oral sugar- and blood-feeding application against dinotefuran and ivermectin, respectively. There was slight cross-resistance detected between topical applied sarolaner and permethrin and larvae treated with sarolaner and spinosad. This study demonstrates sarolaner’s strong potential as both an adulticide and larvicide against Ae. aegypti and warrants further evaluation as a candidate active ingredient for new chemical formulations.