Efficacy of lotilaner against myiasis caused by Cochliomyia hominivorax (Diptera: Calliphoridae) in naturally infested dogs

Abstract

Background The New World screwworm fly, Cochliomyia hominivorax, is widely distributed across South America. This parasitic insect is a significant cause of primary myiasis in animals, including dogs. There is an urgent need for a rapid and efficient treatment to improve the recovery of affected animals. In the present study we evaluated the potential of lotilaner for the treatment of myiasis caused by C. hominivorax larvae in naturally infested dogs. Lotilaner belongs to the isoxazoline class of chemical compounds and is marketed as Credelio™ for use against ticks and fleas in dogs and cats. Methods Eleven dogs with naturally acquired myiasis were enrolled in this study based on the severity of lesions and the number of identified larvae. All animals received a single oral administration of lotilaner at a minimum dose of 20.5 mg/kg body weight. After treatment, the number of expelled larvae, live or dead, was determined at 2, 6 and 24 h, and the larval expulsion rate, larvicidal effect and overall efficacy were calculated. After 24 h, the remaining larvae were removed, counted and identified. The lesions were cleaned, and palliative treatment was administered when necessary, according to the animal's health status. Results All larvae were identified as C. hominivorax. The larval expulsion rate was 80.5% and 93.0% at 2 and 6 h post-treatment, respectively. Lotilaner showed an overall efficacy of 100% at 24 h post-treatment. Conclusions Lotilaner demonstrated a rapid onset of action and a high efficacy against C. hominivorax. We therefore recommend lotilaner for the effective treatment of myiasis in dogs. Graphical Abstract

The current status and outlook for insecticide, acaricide and anthelmintic resistances across the Australian ruminant livestock industries: assessing the threat these resistances pose to the livestock sector

“…48 Of relevance to the livestock industries for the use of this chemical class beyond just for lice is its demonstrated activity against dog ticks in vivo, 118 cattle tick and sheep blowfly in in vitro bioassays, 119 and the myiasis-causing New World screwworm fly in in vivo dog trials. 120,121 Importantly this chemical class has no activity against intestinal nematodes. Another chemical class with applicability to livestock parasites are the cyclooctadepsipeptides.…”

“…Potential for new chemicals to have an impact may lie in the isoxazoline chemical class that has been introduced over recent years for control of ectoparasites in the companion animal market (reviewed by Zhou et al 118 ) and registered recently for use against lice on sheep 48 . Of relevance to the livestock industries for the use of this chemical class beyond just for lice is its demonstrated activity against dog ticks in vivo, 118 cattle tick and sheep blowfly in in vitro bioassays, 119 and the myiasis‐causing New World screwworm fly in in vivo dog trials 120,121 . Importantly this chemical class has no activity against intestinal nematodes.…”