Repellency, prevention of attachment and acaricidal efficacy of a new combination of fipronil and permethrin against the main vector of canine babesiosis in Europe, Dermacentor reticulatus ticks.

Background: Dermacentor reticulatus is a European hard tick of major veterinary importance because it is the vector of canine babesiosis due to Babesia canis. The efficacy against this particular tick species is therefore a key characteristic for an acaricidal solution for dogs. The repellency, prevention of attachment and acaricidal efficacy of Frontline Tri- Act/Frontect, a new combination of fipronil and permethrin against induced infestations of Dermacentor reticulatus ticks on dogs were evaluated after a single topical administration.
Methods: A group of 20 dogs were allocated to two treatment groups. Ten dogs were treated with a topical spot-on formulation containing 6.76% w/v fipronil + 50.48% w/v permethrin once on Day 0 and 10 dogs served as untreated controls. Tick infestations were performed by placing 50 D. reticulatus ticks next to sedated dogs confined to infestation crates on days 1, 7, 14, 21 and 28. Thumb counts on dogs were conducted at 4, 12 and 24 h post-challenge. Tick removal counts were performed 48 h after each infestation. Repellency, prevention of attachment and acaricidal efficacy were calculated.
Results: The new combination provided repellency ranging between (56.5-73.5%) at 4 h post-infestation (pi), between (76.3-92.9%) at 12 h pi and between (83.9-96.5%) at 24 h pi, up to 4 weeks post-treatment. Prevention of attachment ranged between (64.1-79.7%) at 4 h pi, between (79.1-94.2%) at 12 h pi and between (84.2-99.6%) at 24 h pi, up to 4 weeks post-treatment. Acaricidal efficacy against D. reticulatus ticks was ≥99.5% for 4 weeks post-treatment.
Conclusion: The new combination of fipronil and permethrin demonstrated excellent repellency, prevention of attachment and acaricidal efficacy against D. reticulatus for at least 4 weeks. The results suggest that in endemic areas of canine babesiosis, the application of the new combination can significantly reduce the potential for transmission of B. canis as well as other tick-borne diseases.