The science underpinning avian immunology is crucial to understanding basic immunological principles and the exceptional features of the avian immune system, as different strategies birds have adopted can provide important evolutionary insights. This book provides the most complete picture of the avian immune system so far. The world-wide importance of poultry protein for the human diet, the threat of an avian influenza pandemic and heavy reliance on vaccination to protect commercial flocks world-wide demonstrates the need to review the important practical lessons in disease control presented here.