The effect of self-licking behavior on pharmacokinetics of eprinomectin and clinical efficacy against Psoroptes cuniculi in topically administered rabbits

Ear mange mite Psoroptes cuniculi, one of the predominant parasites in rabbits, can cause considerable weight loss, low favorable fee conversion rates, and meningitis. The present experiment was to investigate the difference of plasma disposition and the variation of clinical efficacy under the effect of animal self-licking behavior in topically administered rabbits. Ten rabbits for pharmacokinetic study in two groups (the self-licking and the non-licking) were topically administered with 1 mg kg⁻¹ of eprinomectin. In the self-licking group, rabbits were allowed to self-lick freely, while, to prevent self-licking, each animal in the non-licking group was fitted with a pet collar. Compared to the non-licking group, self-licking behavior contributed to an extremely significant shorter half-life of absorption (14.85 ± 2.79 h in licking group vs. 29.44 ± 7.81 h in non-licking group, p < 0.01) and an extremely significant higher C max value for eprinomectin (21.95 ± 5.36 h in licking group vs. 6.98 ± 0.72 ng ml⁻¹ in non-licking group, p < 0.01) in plasma disposition. An extremely significantly shorter mean residence time (50.72 ± 3.45 h) in self-licking group was also determined compared with the value obtained in non-licking group (106.66 ± 7.39 h; p < 0.01). Clinical efficacy study of eprinomectin was examined in rabbits naturally infested with P. cuniculi which were randomly allocated in three groups: the self-licking, the non-licking, and control groups. All rabbits in the self-licking and the non-licking groups were treated with topical eprinomectin at a single dose of 2 mg kg⁻¹ (day 0). Topical eprinomection led to a complete parasitological recovery in both treated groups on day 14 and remained free of live mites and clinical lesions from day 21 to the end of the study period (day 35).