Laboratory evaluation of the speed of kill of lotilaner (Credelio™) against Ixodes ricinus ticks on dogs

Background: with the geographical expansion of tick species and increased recognition of pathogens they transmit,there is a requirement for safe and rapidly effective control measures for dogs. lotilaner,a novel isoxazoline,is rapidly absorbed following administration of a flavored chewable tablet formulation (credelio™),providing at least 98% efficacy for at least 1 month following assessments at 48 h post-treatment,and following subsequent challenges. a study was conducted to determine the speed with which lotilaner kills ticks. methods: from 38 dogs,the 32 with the highest ixodes ricinus counts from a day -4 infestation were randomized among four groups: two groups were untreated controls,two received lotilaner tablets at a minimum dose rate of 20 mg/kg. infestations with i. ricinus were performed on days -2,7,14,21,28 and 35. counts were completed 4 and 8 h post-treatment (day 0),and 8 and 12 h following subsequent infestations. all live ticks were incubated for 24 h following removal from study dogs. results: at 4 h post-treatment,there was a 69.8% reduction in geometric mean live tick counts in treated dogs compared to controls. after incubation,the reduction increased to 97.2%. at 8 h after treatment,pre- and post-incubation reductions were 99.2 and 100%,respectively. following post-treatment challenges,post-incubation efficacy through day 28 at 8 and 12 h was at least 94.3 and 98.0%,respectively,and was 85.7 and 94.2% at 8 and 12 h after the day 35 challenge. mean live tick counts in the lotilaner groups were significantly lower than in the control groups at all assessments through day 35 at 8 (t (7) ≥ 9,p < 0.0001,days 0 to 28; t (7) = 3.54,p ≤ 0.0095,day 35) and 12 h post-treatment and after subsequent infestations (t (7) ≥ 10,p < 0.0001,all days). there were no treatment-related adverse events. conclusion: lotilaner at a minimum dose rate of 20 mg/kg began to kill ticks on dogs within 4 h of treatment and efficacy was 100% within 8 h. lotilaner sustained a rapid kill of newly infesting i. ricinus through 35 days. by quickly killing ticks that infest dogs,lotilaner has potential to help limit the transmission of tick-borne pathogens. © 2017 the author(s).