Comparative Evaluation of the Efficacy of Two Ectoparasiticides in Preventing the Acquisition of by and : A Canine Ex Vivo Model.

In dogs, tick infestation can cause damage ranging from a simple skin irritation to severe diseases and/or paralysis leading to animal death. For example, and are among the tick species incriminated the most in the transmission of , the agent of human and canine Lyme borreliosis (LB). In this study, we aimed to compare the efficacy of two products designed for dogs-an oral systemic ectoparasiticide and a topical repellent ectoparasiticide-against the acquisition of by adult and using an ex vivo model. Thirty-two beagle dogs were included in a parallel-group-designed, randomized, single-center, negative-controlled efficacy study. The dogs were allocated to three groups based on gender and body weight: a fluralaner (F, Bravecto) treatment group ( = 8), administered a single oral treatment on day 0 at the recommended dose; a dinotefuran-permethrin-pyriproxyfen (DPP, Vectra 3D) treatment group ( = 8), topically treated on day 56 at the recommended dose; and an untreated control group ( = 16). Blood and hair were collected from each dog on days 58, 63, 70, 77, and 84. Hair was added to the silicone-based membrane separating two glass chambers forming the feeding unit (FU). Chamber 1 was filled with blood spiked with sensu stricto, strain B31 (10 cells/mL). Chamber 2, glued below chamber 1, was seeded with 20 adult or . The FUs ( = 240) were incubated at 37 °C with a humidity >90%. Tick survival, attachment, and feces presence were observed from 1 h up to 72 h after tick seeding. The uptake of was determined in ticks using nested polymerase chain reaction (nPCR). The acaricidal efficacy of DPP-treated hair was 100% within 1 h of tick release on every study day for both and . The speed of kill associated with DPP was sufficiently fast to prevent tick attachment and engorgement, and, consequently, to prevent the acquisition of . In the F-treated group, the acaricidal efficacy observed at 12 h, throughout the study, was <20% and <28% for and , respectively. Furthermore, tick feces were observed in the FUs, and several female ticks ( ( = 55) and ( = 94)) tested positive for . The results provide proof of concept for the use of an ex vivo model based on an artificial feeding system to compare two ectoparasiticides against the acquisition of by and . In addition, our results demonstrate the superiority of DPP compared to F in the speed of acaricidal activity against ticks, as well as in preventing the acquisition of .