EVALUATION OF THE PERSISTENCE OF THE EFFECT OF IVERMECTIN AND ABAMECTIN AGAINST GASTROINTESTINAL AND PULMONARY NEMATODES IN CATTLE

The persistence of the effect of ivermectin and abamectin against gast rointestinal nematodes and lungworm in cattle was evaluated in two tri als, each involving 28 animals. Groups of seven cattle either remained untreated, or were treated topically with ivermectin at 500 mu g/kg b odyweight or subcutaneously with either ivermectin or abamectin at 200 mu g/kg bodyweight, Starting on the day of treatment the cattle were given daily trickle infections with various infective nematode larvae for two weeks (Haemonchus species, Trichostrongylus axel and Cooperia species), three weeks (Ostertagia ostertagi and Oesophagostomum radiat um) and four weeks (Dictyocaulus viviparus). The cattle were killed 49 to 51 days after treatment and their worm burdens measured. An effica cy of >99 per cent was recorded in all the groups demonstrating that t he products controlled Haemonchus species, T axei, C oncophora, C punc tata and C surnabada for at least two weeks, O ostertagi and O radiatu m for at least three weeks and D viviparus for at least four weeks.