2006 Volume 59 Issue 9 Pages 607-611
There was a high incidence of sudden death due to haemonchosis in a sheep herd, where a regular anthelmicticprogram using diethylcarbamazine had been conducted. When a new anthelmintic program using ivermectin (IVM) or levamisole (LEV) was conducted over three years, the mortality apparently decreased fromapproximately 20% to 2.8% in the third year. The anthelmintic effects were poor with minimal reduction in eggper gram (EPG) in the pour-on route of IVM, but were significantly higher with a major reduction in the average EPG from 5418.5 to 3.2 in the subcutaneous route of IVM and from 98.2 to 1.9 in the oral route of LEV afteradministration for one month. However, the anthelmintic effects after two months of administration in the subcutaneousroute of IVM were lower than those of the one-month interval, in which the reduction of EPG wasfrom 120.5 to 41.1, indicating no significance. Moreover, despite the significantly higher anthelmintic effectsat first administration of both IVM and LEV for each year, the EPGs were gradually decreased after the secondadministration. This may indicate the occurrence of drug-resistant worms.
