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

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) or doramectin-treated (500 mu g/kg of body weight; 10) groups. Treatments were applied in a single passage along the midline of the back, from the withers to the tailhead. Cattle were euthanatized greater than or equal to 14 days after treatment, and worm burdens were determined by use of standard techniques. Results-Efficacy of doramectin was greater than or equal to 95.3% against adults of Thelazia gulosa, T skrjabini, Dictyocaulus viviparus, Haemonchus contortus, H placei, Ostertagia lyrata, O ostertagi, Trichostrongylus axel, Bunostomum phlebotomum, Capillaria spp, Cooperia oncophora, C pectinata, C punctata, C spatulata, C surnabada, Nematodirus spathiger, Strongyloides papillosus, T colubriformis, Oesophagostomum radiatum, and Trichuris spp. Efficacy was 95.1 % against fourth-stage larvae of D viviparus, H placei, O lyrata, O ostertagi, T axel, 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 greater than or equal to 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.