Laboratory evaluations of the immediate and sustained effectiveness of lotilaner (Credelio™) against three common species of ticks affecting dogs in Europe

Background: There is a continuing need for novel approaches to tick control in dogs. One such approach lies in the ability of lotilaner (Credelio (TM)), an isoxazoline with a rapid onset of action, to provide sustained efficacy against ticks. Two studies were undertaken to confirm lotilaner's efficacy, at the minimum dose rate of 20 mg/kg, against the three most common tick species in Europe. Methods: In each of two studies, 16 Beagle dogs, at least 6 months old, were ranked and blocked by tick counts from infestations placed approximately 1 week before treatment. Within blocks, dogs were randomized to receive either lotilaner flavoured chewable tablets at as close as possible to, but not less than the minimum dose rate of 20 mg/kg, or to be sham-treated controls. Study 1 assessed lotilaner efficacy against concurrent infestations with 50 (+/- 6) Rhipicephalus sanguineus and 70 (+/- 6) Ixodes ricinus; Study 2 infestations were with 50 (+/- 2) Dermacentor reticulatus. Infestations were performed on Day -2 with counts on Day 2, 48 (+/- 2) hours post-treatment. Post-treatment infestations were performed on Days 7, 14, 21, 28 and 35, and ticks were counted 48 (+/- 2) hours post-infestations. Efficacy was determined by the percent reduction in mean live tick counts. Results: Control group infestations for each tick species were adequate for assessing lotilaner efficacy at all assessment times. On Day 2 no live ticks were found on any lotilaner-treated dog. For subsequent counts, in Study 1 lotilaner was 100% effective in eliminating live I. ricinus and R. sanguineus on all but two occasions for each tick; on each of those occasions efficacy was sustained at greater than 98.0%. In Study 2, except for a single unattached live tick found on Day 16, efficacy against D. reticulatus was 100% at every post-treatment assessment. Conclusion: The high and sustained efficacy against the three common species of ticks in Europe, R. sanguineus, I. ricinus and D. reticulatus, demonstrates that lotilaner can be a valuable tool in the treatment of canine tick infestations. Lotilaner flavoured chewable tablets were well tolerated and effectiveness was sustained through at least 35 days.