Worm egg counts in lambs decreased after administration of long acting anthelmintics to ewes

Abstract

Background: One strategy for providing good worm control and to reduce pasture larval contamination is to administer long-acting anthelmintics to lactating ewes. We have previously observed a decrease in the period of protection against 'Haemonchus contortus' in lactating ewes for long-acting anthelmintics on farms with known ML and BZ resistance. Excretion of long-acting anthelmintics in milk has been reported, which may account for our observations of a reduced period of protection in lactating ewes. Hypothesis - The elimination of a proportion of the active constituents of anthelmintics in milk will cause a reduction in worm egg counts (WEC) for untreated lambs, suckling ewes treated with anthelmintics.