Evaluation of the therapeutic efficacy of fluralaner chewable tablets (Bravecto®) against New World screwworm (Cochliomyia hominivorax) infestation in dogs

Abstract Background New World screwworm (NWS), caused by the dipteran Cochliomyia hominivorax , remains a major challenge in Neotropical regions, causing extensive tissue damage and predisposing affected hosts to secondary infections in both humans and animals. Although traditional management has relied on labor-intensive topical treatments, systemic therapies based on isoxazolines offer a more practical alternative. This multicenter clinical study evaluated the therapeutic efficacy of a single oral administration of fluralaner (Bravecto ® ) in dogs naturally infested with C. hominivorax in endemic regions of Brazil. Methods Fifteen client-owned dogs with natural NWS infestations of varying severity were treated with fluralaner chewable tablets at the approved dose range (25–56 mg/kg). Clinical evaluations were performed 24 h after administration. Wounds were examined, and all larvae, whether expelled or still present within the lesions, were collected, counted, and classified according to motility. Live third-instar (L3) larvae expelled after treatment were transferred to pupation substrates and maintained under controlled laboratory conditions to assess adult emergence. Results Treatment achieved 100% wound clearance, with no live larvae remaining within any lesion 24 h after administration. Overall total larvicidal efficacy was 94.36%, reflecting the combined mortality of intralesional and expelled parasites. The larval expulsion rate was 13.99% (206/1,472), and 83 larvae (5.63%) were expelled alive. Notably, none of these live-expelled larvae developed into adult flies (0% emergence), indicating that exposure to fluralaner caused irreversible physiological damage. No adverse events were reported. Conclusions Fluralaner provides a rapid larvicidal effect and represents a practical systemic alternative to conventional treatments, substantially improving the clinical management of canine myiasis. Beyond supporting individual recovery, the complete interruption of the parasite’s life cycle may offer an important epidemiological benefit by reducing environmental contamination. These findings support the potential integration of isoxazolines into public health and One Health strategies aimed at limiting the geographic expansion of NWS outbreaks.