A unique resource for all those interested in the impact of worms on livestock, the anthelmintics used to get rid of them and the emerging problem of anthelmintic resistance. This book provides an over-arching view of past, present and suggested future strategies for control of gastrointestinal nematode parasites in sheep and cattle. The book begins with descriptions of the biology of gastrointestinal nematodes, the harm they cause to the host and their economic impact. The main body of the book deals with the control of worms, focusing on the use of anthelmintic drenches. The relationship between drenching practices and the development of drug resistance is discussed, as well as resistance management. The authors also break new ground by discussing alternative options for worm control, including: nutritional interventions, biological control, breeding for desirable genetics and artificially improving immunity to infection. They also offer useful recommendations for program development.