Comparative study of the efficacy of eprinomectin versus ivermectin, and field efficacy of eprinomectin only, for the treatment of chorioptic mange in alpacas

The efficacy of eprinomectin versus ivermectin (Study 1: a single-centre, randomised, treatment-controlled, blinded field trial), and the field efficacy of eprinomectin (Study 2: a single-centre, open, un-controlled field trial) for the treatment of chorioptic infestation in naturally infested alpacas were assessed in two studies. Thirty alpacas, all positive for Chorioptes sp. mite, were randomly allocated to two treatment groups in Study 1. Group A received a single topical administration of a 0.5% formulation of eprinomectin at the dose rate of 500 μg/kg. Group B received three subcutaneous administrations at 14 days interval of a 1% formulation of ivermectin at the dose rate of 400 μg/kg. Response to treatment was assessed by periodic mite count, and skin lesions scored. In Study 2, one group of 19 alpacas received four administrations at weekly interval of topical eprinomectin at the dose rate of 500 μg/kg, and response to treatment was monitored by mite counts. No localised or systemic side effects were observed in either trial. There was a statistically significant decrease in mite counts on day 7 (P < 0.001) within treatment Groups A and B of Study 1, but mite counts increased again on day 14 and remained high for the duration of the trial in both treatment groups. On day 14 of Study 2, there was a statistically significant reduction in mite counts (P < 0.008) and the mite counts remained very low throughout the remainder of the study. The eprinomectin protocol employed in Study 2, consisting of four weekly topical administrations at the dose rate of 500 μg/kg of body weight, proved highly effective at reducing the Chorioptes mite burden in alpacas.