Pullorum disease of chickens is a bacterial infection caused by Salmonella enterica subspecies
enterica serovar Gallinarum biovar Pullorum (Salmonella Pullorum)
1
. At this time the serovar is
referred to as Gallinarum in some parts of the world and Pullorum in others; in this chapter the
serovar will be referred to as Gallinarum or Pullorum according to the biovar under discussion as
this is more meaningful from a clinical and epidemiological perspective.
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. Ovarian transmission is a major route by which the organism can spread. Game birds
and ‘backyard’ poultry flocks may act as reservoirs of infection, and wild birds may act as vectors
for the organism and as such are important in the epidemiology of the disease.
Fowl typhoid in chickens and turkeys is caused by S. Gallinarum biovar Gallinarum and is more
often observed in the later growing period and in mature stock. Disease is often characterised by
rapid spread with high morbidity and acute or subacute mortality. Red mites may be involved in the
transmission of disease and persistence in poultry houses
Clinical signs in chicks and poults include anorexia, diarrhoea, dehydration, weakness and death. In
mature birds Pullorum disease is less severe but decreased egg production, poor hatchability and
some increased mortality may occur. Fowl typhoid is a more acute septicaemic condition which
mainly affects mature birds and may be particularly severe in commercial laying flocks.