CONTROL OF ESTABLISHED INFECTIONS OF PARASITIC NEMATODES IN CATTLE BYAN IVERMECTIN SUSTAINED-RELEASE INTRARUMINAL BOLUS

Two trials were conducted at separate sites in Europe in order to asse ss the ability of an ivermectin sustained-release (SR) intraruminal bo lus to control established infections of gastrointestinal nematodes an d the lungworm Dictyocaulus viviparus. In each trial, 6 animals were a llocated to each of two groups. One group was untreated (control) and, in the other, each animal received one ivermectin SR bolus. At the ti me of treatment, all animals were harbouring mature infections of seve ral parasitic nematode species. Fourteen days after treatment the anim als were necropsied. In one of the trials, the bolus was >99% effectiv e (p<0.05) against adult Dictyocaulus viviparus, Ostertagia ostertagi, Haemonchus contortus, Nematodirus helvetianus, Trichostrongylus axel, Cooperia spp., Oesophagostomum radiatum, Trichuris discolor and Bunos tomum phlebotomum. In the other trial, similar efficacy was seen (>99% effective, p<0.01); however, sufficient numbers of N. helvetianus, H. contortus and B. phlebotomum were not present in controls for meaning ful analyses to be performed.