Anthelmintic efficacy and pharmacokinetics of pour-on eprinomectin (1 mg/kg bodyweight) against gastrointestinal and pulmonary nematode infections in goats

Abstract

Two controlled studies were performed to assess the efficacy and pharmacokinetics of topical 0.5% w/v eprinomectin (EPRINEX® Pour-on, Merial) against nematode infections of goats. Each study included 16 male castrated goats, less than one year old, harboring induced infections of adult gastrointestinal and pulmonary nematodes. Following blocking on pre-treatment bodyweight and random allocation to one of two groups, half the goats in each study were treated once with eprinomectin (1mg/kg bodyweight, administered topically), and half remained untreated and served as controls. Plasma concentrations of eprinomectin were determined in blood samples collected prior to and at multiple time points up to necropsy. Efficacy was determined based on the nematode counts of the animals following necropsy 14 days after treatment.Efficacy of treatment was 100% against adult Haemonchus contortus, Nematodirus battus, Nematodirus spathiger, Oesophagostomum venulosum, Teladorsagia circumcincta and Dictyocaulus filaria was >94% against adult Cooperia curticei, Trichostrongylus axei and Trichostrongylus colubriformis, and was 89.4% against adult Strongyloides papillosus (p<0.01). Basic pharmacokinetic parameters of eprinomectin (B1a component) for the goats in the two studies were: AUClast, 23.5±5.19/36.0±8.74 day*ng/mL; and Cmax, 3.65±1.12/5.25±1.39ng/mL, respectively; individual maximum plasma concentrations were observed 1 or 2 days after treatment. Results of the studies consistently demonstrated a high therapeutic efficacy of topical eprinomectin at 1mg/kg bodyweight against a broad range of gastrointestinal and pulmonary nematode parasites of goats.