Pullorum disease of chickens is a bacterial infection caused by Salmonella enterica subspecies enterica serovar Gallinarum biovar Pullorum (Salmonella pullorum). In its acute form, Pullorum disease is almost exclusively a septicaemic disease of young chickens. However, the organism may also be associated with disease in turkey poults and may be carried subclinically or lead to reduced egg production and hatchability, plus a range of atypical signs in older birds.