THE PREVALENCE OF ANTHELMINTIC RESISTANCE IN NEMATODE PARASITES OF SHEEP IN SOUTHERN LATIN-AMERICA - PARAGUAY

This survey to detect anthelmintic resistance in nematode parasites of sheep was conducted on 11 farms in the Occidental and 26 farms in the Oriental Regions of Paraguay using the faecal egg count reduction tes t (FECRT). The anthelmintic groups tested were the benzimidazoles, lev amisole and avermectins (both oral and injectable), Overall the levels of resistance were 73%, 68%, 73% and 47%, respectively. Levels of res istance were similar for all three important nematode genera, viz, Hae monchus contortus, Ostertagia and Trichostrongylus. This survey clearl y indicates that a large, and ever increasing, proportion of sheep far mers are rapidly approaching the time when they will have exhausted al l chemotherapeutic options to control parasites. Unless they face havi ng to abandon their sheep farming operations, radical changes will nee d to be implemented with urgency.