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

This survey was conducted in the southern Brazilian state of Rio Grand e do Sul and involved 182 farms located in 26 counties. In addition to the three major broad-spectrum anthelmintic groups (viz. benzimidazol e, levamisole and ivermectin) the combination benzimidazole and levami sole and the H. contortus specific anthelmintic, closantel, were teste d by the faecal egg count reduction method for the prevalence of anthe lmintic resistance, Resistance was found to be 90%, 84%, 13%, 73% and 20%, respectively. This is a crisis situation. Immediate, drastic acti on needs to be implemented, otherwise the sheep industry in this regio n (approx, 10 million head) will soon face a lack of any effective ant helmintics with the inevitable consequences of major restructuring or abandonment.