ACTIVITY OF DORAMECTIN AGAINST NEMATODE ENDOPARASITES OF CATTLE

A series of 28 controlled anthelmintic studies, involving 634 cattle, was conducted throughout North America and Europe to evaluate the effi cacy of doramectin against a broad range of gastrointestinal parasitic nematode species and lungworms in naturally and experimentally infect ed animals. Within each study, one or two groups were treated with dor amectin at 200 mug kg-1 and another group received no drug treatment. Worm burdens were estimated by standardised techniques, and efficacy a ssessed on reduction of worm burdens in doramectin-treated animals. Do ramectin was at least 99.6% effective (P<0.0002) in eliminating the im mature and adult stages of the following 14 species of nematodes: Oste rtagia ostertagi (including inhibited), Ostertagia lyrata, Haemonchus placei, Trichostrongylus axei, Trichostrongylus colubriformis, Cooperi a oncophora (including inhibited), Cooperia pectinata, Cooperia puncta ta, Cooperia spatulata, Cooperia surnabada, Bunostomum phlebotomum, St rongyloides papillosus, Oesophagostomum radiatum and Dictyocaulus vivi parus. Efficacy against adult Trichostrongylus longispicularis, Nemato dirus spathiger and Trichuris spp. was 93.1%,96.5% and 94.6%, respecti vely. Efficacies against adult and fourth-stage larvae of Nematodirus helvetianus, the dose-limiting species, were 73.3% and 75.5%, respecti vely.