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

South America has a large population of small ruminants. Current estim ates are approximately 100 million sheep and 23 million goats. A large percentage of these flocks are raised in the humid tropics/sub-tropic s Nematode parasitism is singly the most important disease of these an imals acid typically farmers resort to frequent anthelmintic treatment in attempts to control this problem. Because of this reliance on drug s, price consideration is an important determinant in a farmer's choic e of anthelmintic, In some circumstances, this has led to unethical pr actices of drug adulteration and substitution, or the offering to farm ers of cheap, sub-standard generic products. The prevalence of anthelm intic resistance has not been investigated in any widespread sense in South America, although some of the first reports of resistance were m ade in southern Brazil almost 30 years ago, The following series of pa pers outline surveys conducted in the humid tropics/sub-tropics of sou thern Latin America to assess the significance of resistance to the br oad-spectrum anthelmintic groups in nematode parasites of sheep flocks .