EFFICACY OF MOXIDECTIN POUR-ON AGAINST GASTROINTESTINAL NEMATODES ANDDICTYOCAULUS-VIVIPARUS IN CATTLE

Twenty crossbred beef heifer calves were used for an efficacy evaluati on of 0.5% moxidectin pour-on against gastrointestinal nematodes and D ictyocaulus viviparus. The latter parasite and Bunostomum phlebotomum were the target species. The calves were exposed to natural infection on pasture from late September to December 22. Additionally, all calve s were experimentally infected with B. phlebotomum at 71 and 29 days b efore treatment and with D. viviparus at 29 days before treatment. The 20 calves were randomly allocated into two groups of ten, based on pr esence of patent lungworm and hookworm infections on days -6 and -1. T reatments were as follows: Group A, moxidectin 0.5% pour-on (PO) at 50 0 mu g kg(-1) BW; Group B, moxidectin vehicle (controls) by PO applica tion. General strongyle and hookworm egg counts and lungworm larval co unts were reduced to zero at 13 days after moxidectin treatment; treat ment effect was significant(P < 0.05) only for the strongyle and hookw orm counts. Percentage reduction for adult hookworms and mature-immatu re adult lungworms was 100.0 and also for adults and L(4) Haemonchus p lacei and Ostertagia ostertagi and Trichostrongylus axel adults, adult males of Cooperia pectinata and C. spatulata, and Oesophagostomum rad iatum adults. Efficacy values for C. punctata adult males, Cooperia sp p. adult females, and Cooperia spp. L(4) were > 99.9%, > 99.9%, and 92 .4%, respectively. All efficacy values were significant (alpha = 0.05, 1-sided) except for Cooperia spp. L(4).