Welfare implications of bacterial and viral infectious diseases for laying hens

摘要

Bacterial and viral infectious diseases are significant welfare concerns as they cause a range of clinical signs and mortality depending on the body system(s) affected and severity of the disease. Basic skills in the detection of the clinical signs in poultry and provisional diagnosis of the infectious disease is important for the immediate course of action that needs to be taken to eliminate or reduce the impact of the disease on bird's welfare. Therefore, in this chapter, bacterial and viral diseases of laying hens (chickens) have been described on the basis of their clinical signs and lesions, as opposed to the classes of infecting bacterial or viral agents. Diseases causing sudden death, respiratory illness, ill thrift, diarrhoea, lameness or recumbency, and reduced egg production and quality are discussed.