Efficacy of a topical formulation of eprinomectin against endoparasites of cattle in New Zealand

Abstract

Two controlled studies involving 24 cattle were conducted in New Zealand to determine the efficacy of a topical, non-flammable formulation of eprinomectin against induced and naturally acquired nematode infections. In Trial 1, nematode infections were induced on Day -5 with third-stage larvae of Cooperia spp., Haemonchus contortus, Ostertagia ostertagi and Trichostrongvlus 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 faecal 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 according to bodyweight to one of two treatments: untreated control or eprinomectin (0.5% w/v) applied topically at 1 ml/10 kg bodyweight. Necropsies were undertaken on Days 14 and 15 and total nematode counts were done. In Trial 1, cattle treated with eprinomectin had significantly (p < 0.05) fewer Cooperia spp. and O. ostertagi than the controls. Larvae of H. contortus and T. colubriformis did not establish. In Trial 2, cattle treated with eprinomectin had significantly (p < 0.05) fewer of the following parasites than the controls: Haemonchus spp. (adult), Cooperia surnabada (adult), C. oncophora (adult), Cooperia spp. (L,), Ostertagia lyrata (adult), O. ostertagi (adult), Oesophagostomum spp. (adult), T. avei (adult and L1) and Trichuris spp. (adult). Reductions of 100% were observed for Capilfaria spp. (adult), D. viviparus (adult and L,), and Nematodirus helvetianus (adult), but these were not statistically significant (p > 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 indicate that eprinomectin in a topical formulation is a highly effective nematocide in cattle.

Activity of eprinomectin in goats against experimental infections with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis

“…This is the first study to demonstrate the high activity of eprinomectin against gastrointestinal nematodes in goats when applied topically at 0.5 mg/kg bodyweight. These results are consistent with the very high nematocidal activity described in cattle by previous workers against natural or induced infections: efficacy of between 99 and 100 per cent has been recorded against adult strongyles of Ostertagia species, Haemonchus species, Nematodirus species, Oesophagostomum species and inhibited larval strongyles of Ostertagia species, when given topically at 0.5 mg/kg bodyweight (Shoop and others 1996b, Gogolewski and others 1997, Pitt and others 1997, Williams and others 1997, Yazwinski and others 1997). Nevertheless, the less than complete efficacy against T colubriformis in the present study indicates that this nematode species is probably the dose‐limiting parasite for eprinomectin in goats and that the dose rate of 0.5 mg/kg when given topically could be considered as a suboptimal dosage.…”

Probable multigeneric resistance to macrocyclic lactone anthelmintics in cattle in New Zealand

“…Both were also previously shown by means of controlled slaughter trials to be highly effective ( 99% effi cacy) against C. oncophora in cattle (Shoop et al 1996;Gogolewski et al 1997;B Loveridge, unpublished), but comparable data relating to their effi cacy against T. longispicularis Table 1. Abomasal and small intestinal worm counts in 6-8-month-old mixed-breed calves that were untreated or treated with topical formulations of either eprinomectin or abamectin, 7-10 days previously.…”

Efficacy of eprinomectin pour‐on against gastrointestinal nematodes and the nasal bot fly (Oestrus ovis) in sheep

“…The efficacy of topical applications of eprinomectin against parasitic nematodes of the gastrointestinal tract has been assessed in cattle and goats (Shoop and others 1996b, Gogolewski and others 1997, Pitt and others 1997, Yazminski and others 1997, Chartier and others 1999). In sheep, its efficacy was first investigated after an oral dose (Shoop and others 1996a), but more recently Cringoli and others (2003) have investigated a pour‐on formulation.…”