Successful microencapsulation of fluralaner and its potential as a larvicide for vector control

In the US, fluralaner is currently exclusively labeled for use against ectoparasites in companion animals and poultry, but has efficacy against several off-label fly species. Chemical insecticides are often the primary action in attempt to control insect pest species, yet only a handful of active ingredients are available to target Dipteran larvae. In anticipation of adding another chemical class into rotation, we tested a novel, proprietary yeast microencapsulated (YME) formulation of fluralaner against three larval pest species: Ae. albopictus, C. sonorensis, and M. domestica. YME fluralaner was reconstituted in water at concentrations of 0.00001-0.1mg/mL (Aedes and Culicoides) or 1-50mg/mL (Musca) for use in dose-response assays. The three larval species that were evaluated in this study have distinct habitats, and the application methods and media-types used during bioassays reflects that. M. domestica is terrestrial, thus the formulated product was added to solid media, while both C. sonorensis and Ae. albopictus larvae are aquatic, so product efficacy was evaluated by applying to liquid media (water). 5-20 late-stage larvae were immediately added to each petri dish of media following the addition of fluralaner. For each species, the LC₅₀ at 24h was estimated using probit analysis. YME fluralaner was highly effective against all species tested: Ae. albopictus LC₅₀=0.000077mg/mL; C. sonorensis LC₅₀=0.00067mg/mL; M. domestica LC₅₀=2.58mg/mL. YME fluralaner shows promise for controlling larval insects that naturally feed on detritus, thereby bypassing cuticular penetration barriers and safely delivering the active ingredient to the target species.