Efficacy of topically administered doramectin against eyeworms, lungworms, and gastrointestinal nematodes of cattle

Abstract

Objective - To evaluate efficacy of topically administered doramectin against eyeworms, lungworms, and gastrointestinal nematodes of cattle. Animals - 400 cattle (20 cattle in each of 20 trials). Procedure - Trials were conducted in North America; natural and experimentally induced infections were used. In each trial, cattle were allocated randomly to control (placebo [saline {0.9% NaCl} solution at 1 ml/10 kg of body weight] or untreated; n = 10) groups. Treatments were applied in a single passage along the midline of the back, from the withers to the tailhead. Cattle were euthanatized ≥ 14 days after treatment, and worm burdens were determined by use of standard techniques. Results - Efficacy of doramectin was ≥ 95.3% against adults of Thelazia gulosa, T skrjabini, Dictyocaulus vivparus, Haemonchus contortus, H placei, Ostertagia lyrata, O ostertagi, Trichotrongylus axei, Bunostomum phlebotomum, Capillaria spp, Cooperia oncophora, C pectinata, C punctata, C spatulata, C surnabada, Nematodirus spathiger, Strongyloides papillosus, T colubriformis, Oeso-phagostomum radiatum, and Trichuris spp. Efficacy was 95.1% against fourth-stage larvae of D vivparus, H placei, O lyrata, O ostertagi, T axei, C oncophora C punctata, C spatulata, C surnabada, N helvetianus, T colubriformis, O radiatum, and Trichuris spp. In addition, efficacy against inhibited fourth- stage larvae of O ostertagi and Ostertagia spp was ≥ 98.1%. Conclusions and Clinical Relevance - A single topical application of doramectin pour-on was efficacious against a broad range of nematode species in cattle.