Animal breeders and veterinarians have become increasingly interested in breeding strategies aimed at improving disease resistance in farm animals, as this lessens farmers' dependence on the use of drugs at a time when there is concern about their high usage in animals to be used for food products. There has also been concern at the level of drug resistance now shown by many disease organisms, and the cost of veterinary drugs in developing countries. This book consists of 27 chapters by leading international research workers from the UK, USA, Canada, Europe, Africa and Australasia reviewing our current knowledge in this area, and should interest workers in animal breeding and genetics, parasitology, animal production and veterinary medicine.