Anthelmintic activity of injectable eprinomectin (eprecis® 20 mg/mL) in naturally infected dairy sheep.

The anthelmintic activity of an injectable eprinomectin formulation (Eprecis® 20 mg/mL) was evaluated in 150 naturally infected dairy sheep raised in 3 semi-intensive flocks. All ewes were at the same stage of lactation and grazed on natural pastures. Ewes did not receive any anthelmintic treatment for at least 4 months prior to the experiment. In each flock, 50 ewes were selected and randomly allocated to control (C) or treatment (T) groups (n = 25 per group). Groups were balanced according to the ewes' bodyweight (BW) and fecal egg count (FEC) measured seven days before eprinomectin administration (day-7). On study day 0, ewes in group T, received 0.2 mg/kg BW of eprinomectin subcutaneously (Eprecis® 20 mg/mL, Ceva). Ewes in group C were left untreated. Fecal samples were collected on day 0, 7, 14, 21 and 28 post-treatment to assess FEC and for coprocultures. Ewes were weighed on day 0 and 28. Overall and within-flock efficacy of eprinomectin was calculated throughout the experimental period. No local or general adverse reaction after injection was observed. The most prevalent parasite genera were Teladorsagia, Haemonchus and Trichostrongylus. Following treatment, the overall mean FEC of C and T groups differed significantly (P < 0.001). Overall and within-flock efficacy of eprinomectin was 99.8%-100.0% and 99.7%-100.0%, respectively. Contrary to C group, ewes treated with injectable eprinomectin increased their BW during the study (-0.5 kg vs. + 1.5 kg, P < 0.001). In this field study, a single subcutaneous injection of eprinomectin to dairy sheep, at 0.2 mg/kg BW, resulted in excellent curative anthelmintic activity; egg counts remain low for at least 28 days after treatment.