Towards the eradication of Haemonchus contortus from sheep flocks in Sweden.

Previous studies have shown that between-year transmission of Haemonchus contortus in Swedish sheep flocks is almost entirely as over-wintered populations within housed animals, and not on pasture. This suggests that eradication of this parasite is a realistic possibility. Thus, two sheep farms with a history of H. contortus infection on the Swedish island of Oland were selected for study. During the winter housing period of 2003/2004 all ruminants (sheep and cattle) on both farms were treated with ivermectin. Monitoring by faecal egg counts and infective larval differentials of ewes and lambs for the subsequent two grazing seasons, together with total abomasal worm counts of 10 lambs from each farm at the end of the first grazing year, showed that this objective was achieved.