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

This survey was conducted on 252 farms randomly distributed over all t he sheep raising areas in Uruguay. The study involved farms with more than 500 sheep, which represented 80% of the total sheep population of the country. Three anthelmintic groups were assessed, namely, benzimi dazoles, levamisole and avermectins, Overall, the results showed 80% o f sheep flocks had benzimidazole resistance, 71% had resistance to lev amisole, and 1.2% of flocks showed resistance to avermectins, Approxim ately 28% of farms had resistance to one anthelmintic group, 64% to tw o anthelmintic groups, and 1% resistance to all three groups, Only 7.5 % of farms had no detectable levels of anthelmintic resistance, More t han 80% of farms had Trichostrongylus populations resistant to both be nzimidazoles and levamisole, Resistance was recorded in all three anth elmintic groups for Haemonchus and resistance also occurred to benzimi dazoles and levamisole in Osteragia.