The Veterinary Record, Vol 140, Issue 11, 278-279
Copyright © 1997 by British Veterinary Association

Evaluation of the persistence of the effect of ivermectin and abamectin against gastrointestinal and pulmonary nematodes in cattle

¹ Merck Research Laboratories, Kathrinenhof, D-83101 Rohrdorf, Germany
² Merck Research Laboratories, PO Box 2000, Rahway, New Jersey 07065, USA
³ Merck Research Laboratories, Missouri Farm, 6498 Jade Road, Fulton MO 65251, USA
⁴ Merck AgVet Division, PO Box 2000, Rahway, New Jersey 07065, USA

The persistence of the effect of ivermectin and abamectin against gastrointestinal nematodes and lungworm in cattle was evaluated in two trials, each involving 28 animals. Groups of seven cattle either remained untreated, or were treated topically with ivermectin at 500 µg/kg bodyweight or subcutaneously with either ivermectin or abamectin at 200 µg/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 axei and Cooperia species), three weeks (Ostertagia ostertagi and Oesophagostomum radiatum) and four weeks (Dictyocaulus viviparus). The cattle were killed 49 to 51 days after treatment and their worm burdens measured. An efficacy of >99 per cent was recorded in all the groups demonstrating that the products controlled Haemonchus species, T axei, C oncophora, C punctata and C surnabada for at least two weeks, O ostertagi and O radiatum for at least three weeks and D viviparus for at least four weeks.