Treatment of dogs with Bravecto® (fluralaner) reduces mosquito survival and fecundity

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Background: Mosquitoes serve as the vector of canine heartworm (Dirofilaria immitis), which represents a significant and persistent threat to canine health. A reduction in the longevity and/or reproductive success of mosquitoes that take a bloodmeal from fluralaner-treated dogs may consequently reduce the local transmission of heartworm and prevent new infections. This study investigated a novel secondary effect of an oral formulation of the ectoparasiticide fluralaner (Bravecto®) against a laboratory strain of mosquito (Aedes aegypti). Methods: Six dogs were administered a single dose of fluralaner orally in the form of Bravecto® Chews (at the labeled fluralaner dose of 25 mg/kg body weight) while six control dogs received no treatment. Mosquitoes were fed on blood collected from each dog; this was performed prior to treatment and weekly for 15 weeks posttreatment to assess the continued duration of effects as serum fluralaner levels decrease. Mosquito fitness was assessed by three parameters: rate of successful blood feeding, survival, and egg laying. Results: Blood feeding was equally successful between control and treatment groups. Fluralaner treatment significantly reduced mosquito survival within the first day of blood feeding for 12 weeks posttreatment (efficacy range = 33.2% – 73.3%). Survival of mosquitoes to a potentially heartworm-infective timepoint (14 days postfeeding) was significantly reduced in the fluralaner-treated group at several timepoints, but less consistently (weeks 1, 2, 5, 11, 12, 13, 14, and 15; efficacy range = 49.4% – 91.4%). Egg laying by mosquitoes was almost completely suppressed for the first 13 weeks following treatment (treatment efficacy = 100%). Conclusions: Mosquitoes fed blood from fluralaner-treated dogs experienced a significant reduction in survival and fecundity. These findings support the potential for reduction in heartworm transmission directly by lethal effects on the vector and indirectly by reduction of the local vector population when mosquitoes are exposed to treated animals.