Fowl typhoid is caused by Salmonella enterica serotype Gallinarum biovar Gallinarum and is characterized by mortality rates in young birds similar to those of Salmonella enterica serotype Gallinarum biovar Pullorum, although mortality rates of S Gallinarum are possibly higher in older birds. Younger birds are anorectic, weak, and depressed, and they have white fecal material pasted to the vent area. Affected birds may also have respiratory disease, blindness, or swollen joints. Older birds may be pale and dehydrated and have diarrhea. Lesions in older birds may include a swollen, friable, and often bile-stained liver, with or without necrotic foci; enlarged spleen and kidneys; anemia; and enteritis. Diagnosis is based on isolation and identification of the organism. The goal for control of fowl typhoid is elimination of the pathogen; therefore, treatment is not recommended.
Among salmonelloses of poultry, fowl typhoid is among those of greatest economic importance to the poultry industry worldwide. The National Poultry Improvement Plan (NPIP) has been responsible for eradication of fowl typhoid from domestic poultry of the United States.
Etiology of Fowl Typhoid
The causative agent of fowl typhoid is Salmonella enterica enterica serovar Gallinarum biovar Gallinarum (S Gallinarum). S Gallinarum is a gram-negative, nonmotile, host-adapted avian pathogen belonging to Salmonella serogroup D.
Epidemiology of Fowl Typhoid
The incidence of fowl typhoid is low in the US, Canada, and some European countries but much higher in other countries.
Although S Gallinarum is egg-transmitted and produces lesions in chicks and poults similar to those produced by S enterica serotype Gallinarum biovar Pullorum, S Gallinarum has a much greater tendency to spread among growing or mature flocks. The mortality rate in young birds is similar to that in S Pullorum infection but may be higher in older birds.
Clinical Findings and Lesions of Fowl Typhoid
Fowl typhoid may be acute or chronic. Clinical signs and lesions in young birds are similar to those observed with S Pullorum infection (see the liver, ovary, and heart lesion photographs). Older birds may be pale and dehydrated and have diarrhea.
Lesions in older birds may include the following:
swollen, friable, and often bile-stained liver, with or without necrotic foci
enlarged spleen and kidneys
anemia
enteritis
Enlarged liver with multiple white, coalescing necrotic lesions throughout, in an adult chicken infected with Salmonellaenterica serotype Gallinarum biovar Gallinarum.
Courtesy of Dr. Guillermo Zavala.
Multiple flaccid or regressing ova with prominent thecal blood vessels in the ovary in an adult chicken infected with Salmonellaenterica serotype Gallinarum biovar Gallinarum.
Courtesy of Dr. Guillermo Zavala.
Multiple petechial hemorrhages in the myocardium and the epicardial fat in an adult chicken infected with Salmonellaenterica serotype Gallinarum biovar Gallinarum.
Courtesy of Dr. Guillermo Zavala.
Enlarged liver with multiple white, coalescing necrotic lesions throughout, in an adult chicken infected with Salmonellaenterica serotype Gallinarum biovar Gallinarum.
Courtesy of Dr. Guillermo Zavala.
Multiple flaccid or regressing ova with prominent thecal blood vessels in the ovary in an adult chicken infected with Salmonellaenterica serotype Gallinarum biovar Gallinarum.
Courtesy of Dr. Guillermo Zavala.
Multiple petechial hemorrhages in the myocardium and the epicardial fat in an adult chicken infected with Salmonellaenterica serotype Gallinarum biovar Gallinarum.
Courtesy of Dr. Guillermo Zavala.
Diagnosis of Fowl Typhoid
Isolation and identification of the causative agent
Clinical signs and lesions of fowl typhoid are similar to those of pullorum disease, which is caused by S Pullorum. Therefore, diagnosis should be confirmed by isolation, identification, and serotyping of S Gallinarum (National Poultry Improvement Plan testing procedure).
Treatment and Control of Fowl Typhoid
Treatment: not recommended
Control: eliminating the disease
Treatment and control of fowl typhoid are as for pullorum disease, as outlined in the National Poultry Improvement Plan.
There are no federally licensed vaccines in the US. In other countries, vaccines (killed or live attenuated) made from a rough strain of S Gallinarum (9R) have had variable results in controlling mortality rates. Vaccines derived from outer membrane proteins, mutant strains, and a virulence-plasmid-cured derivative of S Gallinarum have shown promise in protecting birds against challenge.
The standard serological tests for pullorum disease also detect fowl typhoid.
Key Points
Clinical signs and lesions of S Gallinarum in young chickens and turkeys are similar to those caused by S 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 Gallinarum is through isolation and identification. The National Poultry Improvement Plan outlines measures for elimination of the disease.
For More Information
Gast RK, Porter RE. Salmonella infections. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry, 14th ed. Wiley-Blackwell; 2020:719-753.
USDA Animal and Plant Health Inspection Service (APHIS). National Poultry Improvement Plan (NPIP).
Fulton RM. Bacterial diseases. In: Boulianne M, ed. Avian Disease Manual. 8th ed. American Association of Avian Pathologists; 2019:101-108.
