Efficacy of eprinomectin 5 mg/mL topical solution administered twice pour on at 1 mg per kg body weight against sarcoptic mange (Sarcoptes scabiei) in sheep

Sarcoptic mange of sheep is a skin disease which compromises the health and welfare of the animals, impacts their productivity and is zoonotic. In Europe, sarcoptic mange appears to be the prevailing type of mange affecting sheep kept for milk production in the Mediterranean countries. Eprinomectin 5 mg/mL topical solution (EPRINEX® Multi, Boehringer Ingelheim) was recently authorized for the treatment of gastrointestinal and pulmonary nematodes and Oestrus ovis in sheep with zero hours milk withdrawal in several countries in Europe. As the product in cattle has claims against a broad range of parasites including sarcoptic mange mites, the therapeutic efficacy of the product was evaluated in dairy sheep with naturally acquired S. scabiei infestation in two field efficacy study (25 sheep per study) and one controlled, masked clinical study (22 sheep) conducted in Greece. In the field studies, all animals were administered twice, two weeks apart (Days 0 and 14), eprinomectin 5 mg/mL topical solution at 14 mL per animal pour on, based on the body weight measured for the visually estimated heaviest five animals in each study. In the controlled study, animals were ranked by decreasing pre-treatment live mite count, formed in blocks of two animals and randomly assigned to one of two groups to remain untreated (control) or to be administered twice, two weeks apart, eprinomectin 5 mg/mL topical solution at 1 mL per 5 kg body weight pour on. Skin scrapings were collected prior to treatment and at intervals for eight weeks after the first treatment to establish live Sarcoptes mite counts. A 'Mange Clinical Score' was established for each animal using a 5-category scoring system at each sampling. Mite counts of the eprinomectin 5 mg/mL topical solution-treated animals were significantly (p < 0.0001) lower than the pre-treatment counts in the field studies or those of the controls in the controlled study, on all occasions post-treatment. All treated animals had zero live mite counts at 28 days after the first treatment and at the subsequent occasions until the end of the studies (Day 56). All untreated animals in the controlled study remained infested throughout the study. The 'Mange Clinical Score' of the eprinomectin 5 mg/mL topical solution-treated animals, compared either to the pre-treatment scores in the animals in the field studies or to the scores of the controls in the controlled study, improved significantly (p < 0.05) from Day 7 or Day 14, respectively. At the end of the studies, 56 of the 61 treated sheep had healthy skin and did not show clinical symptoms associated with sarcoptic mange, while five animals still presented small, reddened skin areas and some itching despite demonstrating zero mite counts over four weeks. The administration of the treatments was well accepted by all animals and no health problems were observed throughout the studies. This series of studies demonstrated eprinomectin 5 mg/mL topical solution when administered twice, two weeks apart, to be an efficacious and safe treatment against ovine sarcoptic mange.