The causal agent of fowl typhoid is Salmonella enterica Gallinarum. The incidence of fowl typhoid is low in the USA, Canada, and some European countries but is much higher in other countries. Although S enterica Gallinarum is egg-transmitted and produces lesions in chicks and poults similar to those produced by S enterica Pullorum, there is a much greater tendency to spread among growing or mature flocks. Mortality in young birds is similar to that seen in S enterica Pullorum infection but may be higher in older birds.
Fowl typhoid may be acute or chronic. Clinical signs and lesions in young birds are similar to those seen with S enterica Pullorum infection. Older birds may be pale, dehydrated, and have diarrhea.
Lesions in older birds may include:
Diagnosis should be confirmed by isolation, identification, and serotyping of S enterica Gallinarum (National Poultry Improvement Plan testing procedure).
Treatment and control are as for Pullorum disease. There are no federally licensed vaccines in the USA. In other countries, vaccines (killed or modified live) made from a rough strain of S enterica Gallinarum (9R) had variable results in controlling mortality. More recently, vaccines derived from outer membrane proteins, mutant strains, and a virulence-plasmid-cured derivative of S enterica Gallinarum have shown promise in protecting birds against challenge. The standard serologic tests for Pullorum disease also detect fowl typhoid.
Clinical signs and lesions of S enterica Gallinarum in young chickens and turkeys are similar to those caused by S enterica Pullorum. including cecal cores and nodular lesions in the liver, spleen, lungs, heart, gizzard, and intestines.
Lesions in older birds include swollen, friable, bile-stained and necrotic lesions in the liver, in addition to enteritis and enlargement of the spleen and kidneys.
Confirmation of S enterica Pullorum is through isolation and identification. The National Poultry Improvement Plan outlines measures for elimination of the disease.