Preventative biosecurity is now a prerequisite to poultry production; poultry producers worldwide are taking the necessary steps to establish strict biosecurity programmes to eliminate pathogenic organisms from the farm environment. Routine farm practices such as terminal disinfection of empty sheds, equipment, disinfection of incoming vehicles, control of aerial respiratory transmission, sanitation of hatchery equipment and preparing footbath prevent the horizontal transmission of disease which can spread rapidly through the flock under intensive poultry production conditions.