EFFICACY OF A TOPICAL FORMULATION OF EPRINOMECTIN AGAINST ENDOPARASITES OF CATTLE IN NEW-ZEALAND

Two controlled studies involving 24 cattle were conducted in New Zeala nd to determine the efficacy of a topical, non-flammable formulation o f eprinomectin against induced and naturally acquired nematode infecti ons. In Trial 1, nematode infections were induced on Day -5 with third -stage larvae of Cooperia spp., Haemonchus contortus, Ostertagia oster tagi and Trichostrongylus colubriformis so that the nematodes would be at the fourth larval stage when the cattle were treated. In Trial 2, cattle had naturally acquired nematode infections as determined by fae cal nematode egg counts and larval cultures. The cattle were allocated on Day 0 (Trial 1) or Day -6 (Trial 2) on a stratified random basis a ccording to bodyweight to one of two treatments: untreated control or eprinomectin (0.5% w/v) applied topically at 1 ml/10 kg bodyweight. Ne cropsies were undertaken on Days 14 and 15 and total nematode counts w ere done. In Trial 1, cattle treated with eprinomectin had significant ly (p < 0.05) fewer Cooperia spp. and 0. ostertagi than the controls. Larvae of H. contortus and T. colubriformis did not establish. In Tria l 2, cattle treated with eprinomectin had significantly (p < 0.05) few er of the following parasites than the controls: Haemonchus spp. (adul t), Cooperia surnabada (adult), C. oncophora (adult), Cooperia spp. (L (4)), Ostertagia lyrata (adult), 0. ostertagi (adult), Oesophagostomum spp. (adult), T. axei (adult and L(4)) and Trichuris spp. (adult). Re ductions of 100% were observed for Capillaria spp. (adult), D. vivipar us (adult and L(4)), and Nematodirus helvetianus (adult), but these we re not statistically significant > 0.05) because four or fewer control animals were infected with these parasites. In Trial 2, efficacies of greater than 99% were observed against all species for which moderate to high burdens occurred in the untreated controls. These findings in dicate that eprinomectin in a topical formulation is a highly effectiv e nematocide in cattle.