Chorioptic mange in dairy cattle: treatment with eprinomectin pour-on.

A randomized block design study was conducted to confirm the efficacy of topical eprinomectin against naturally acquired Chorioptes bovis mite infestations. Twelve adult Simmentaler Fleckvieh cattle were formed into six replicates of two animals based on pretreatment mite counts. Within replicates, animals were randomly allocated to untreated controls or were treated with eprinomectin 0.5% pour-on solution at 1 mL/10 kg body weight (0.5 mg eprinomectin/kg body weight). Live mites were counted, and mange lesions were scored prior to treatment and at weekly intervals until the end of the study on day 56. Feed consumption was recorded daily throughout the study, and body weights were measured. Differences between variables were declared significant if p < or = 0.05. Mite counts for the cattle treated with eprinomectin were reduced by 100% from day 14 through the end of the study (p < 0.05). At each examination from day 21 through the end of the study, treated animals were significantly clinically improved as measured by lesion scoring compared with untreated controls. Weight gain and feed conversion efficiency were numerically higher in the eprinomectin-treated group. Results of this study demonstrate a positive response in growth rate following effective treatment of cattle for chorioptic mange and underline the economic importance of the parasite and the value of treatment.