Pullorum disease is caused by vertically transmitted Salmonella enterica serotype Gallinarum biovar Pullorum and is characterized by very high mortality rates in young chickens and turkeys. Affected birds huddle near the heat source; are anorectic, weak, and lethargic; and have white fecal material pasted to the vent area. Affected birds may also have respiratory disease, blindness, or swollen joints. Serological testing is used as a surveillance tool; however, because of the potential for false-negative or false-positive results, definitive diagnosis is made by isolation and identification of the organism. The goal for control of pullorum disease is elimination of the pathogen, particularly from breeding flocks; therefore, treatment is not recommended.
Pullorum disease is responsible for considerable economic losses in the poultry industry worldwide. In the US, pullorum disease also has a program overseen by the National Poultry Improvement Plan (NPIP) through the USDA. Historically, pullorum disease was known as "bacillary white diarrhea."
Etiology of Pullorum Disease in Poultry
Pullorum disease is caused by infection with Salmonella enterica enterica serovar Gallinarum biovar Pullorum (S Pullorum). S Pullorum are gram-negative nonsporogenic rods measuring 1.0–2.5 mcm by 0.3–1.5 mcm. They are nonmotile under normal conditions and exhibit host specificity for poultry.
Epidemiology of Pullorum Disease in Poultry
Infections with S Pullorum are usually vertically transmitted and cause very high mortality rates (potentially approaching 100%) in young chickens and turkeys within the first 2–3 weeks after hatching. In adult chickens, mortality rates may be high; however, frequently there are no clinical signs.
Pullorum disease was once common but has been eradicated from commercial poultry stock in the US, although it may occur in other avian species (eg, guinea fowl, quail, pheasants, sparrows, parrots, canaries, and bullfinches) and in small backyard or hobby flocks. Infection in mammals is rare, although experimental and natural infections have been reported (chimpanzees, rabbits, guinea pigs, chinchillas, pigs, kittens, foxes, dogs, swine, mink, cows, and wild rats).
Transmission is usually vertical (transovarian) but also occurs via direct or indirect contact (respiratory or fecal) with infected birds or contaminated feed, water, or litter. Infection transmitted via egg or hatchery contamination usually results in death during the first few days of life up to 2–3 weeks. Transmission between farms is due to poor biosecurity.
Clinical Findings and Lesions of Pullorum Disease in Poultry
Pullorum disease may occur in all age groups; however, birds < 4 weeks old or younger are most commonly affected. Birds may die in the hatchery shortly after hatching.
Affected birds exhibit the following clinical signs:
huddling near a heat source
anorexia
weakness
whitish fecal pasting around the vent (diarrhea)
Survivors are small in size and frequently become subclinically affected carriers with localized infection of the ovary. Some of the eggs laid by such hens hatch and produce infected progeny.
Multifocal granulomatous splenitis (evident as raised, 1- to 5-mm white nodules) in an adult chicken, due to infection by Salmonella enterica serotype Gallinarum biovar Pullorum.
Courtesy of Dr. David E. Swayne.
Severe, diffuse granulomatous pericarditis in an adult chicken, due to infection by Salmonella enterica serotype Gallinarum biovar Pullorum.
Courtesy of Dr. David E. Swayne.
Gross pathology photograph of the ovary, oviduct, and adnexa of a chicken with oophoritis caused by infection by Salmonella enterica serotype Gallinarum biovar Pullorum. Note the pedunculated involuting ovarian follicles of abnormal shape containing white granuloma (arrows) interspersed with small, grossly normal ovarian follicles. These findings are nonspecific and may be similar to other ovarian infections.
Courtesy of Dr. David E. Swayne.
Multifocal granulomatous hepatitis (evident as raised, 1- to 5-mm white nodules) in a chicken liver, in addition to nodular myocarditis due to infection by Salmonella enterica serotype Gallinarum biovar Pullorum.
Courtesy of Dr. David E. Swayne.
Multifocal granulomatous splenitis (evident as raised, 1- to 5-mm white nodules) in an adult chicken, due to infection by Salmonella enterica serotype Gallinarum biovar Pullorum.
Courtesy of Dr. David E. Swayne.
Severe, diffuse granulomatous pericarditis in an adult chicken, due to infection by Salmonella enterica serotype Gallinarum biovar Pullorum.
Courtesy of Dr. David E. Swayne.
Gross pathology photograph of the ovary, oviduct, and adnexa of a chicken with oophoritis caused by infection by Salmonella enterica serotype Gallinarum biovar Pullorum. Note the pedunculated involuting ovarian follicles of abnormal shape containing white granuloma (arrows) interspersed with small, grossly normal ovarian follicles. These findings are nonspecific and may be similar to other ovarian infections.
Courtesy of Dr. David E. Swayne.
Multifocal granulomatous hepatitis (evident as raised, 1- to 5-mm white nodules) in a chicken liver, in addition to nodular myocarditis due to infection by Salmonella enterica serotype Gallinarum biovar Pullorum.
Courtesy of Dr. David E. Swayne.
There may be no lesions due to an acute septicemia and death. Lesions in young birds usually include unabsorbed yolk sacs and classic gray nodules in the liver, spleen, lungs, heart, gizzard, and intestine. Firm, cheesy material in the ceca (cecal cores) and raised plaques in the mucosa of the lower intestine are sometimes present. Occasionally, synovitis is prominent.
Adult carriers usually have no gross lesions but may have nodular pericarditis, fibrinous peritonitis, or hemorrhagic, atrophic, regressing ovarian follicles with caseous contents. In mature chickens, chronic infections produce lesions indistinguishable from those of fowl typhoid (see granulomatous splenitis, pericarditis, oophoritis, and hepatitis images).
Diagnosis of Pullorum Disease in Poultry
Serological testing to detect potentially positive birds
Isolation, identification, and serotyping to confirm infection
Lesions may be highly suggestive; however, diagnosis should be confirmed by isolation, identification, and serotyping of S Pullorum. Infections in mature birds can be identified by serological tests, followed by necropsy evaluation complemented by microbiological culture and typing for confirmation.
Official testing recommendations for flocks in the US are outlined in the National Poultry Improvement Plan (NPIP). The NPIP lists approved rapid assays for Salmonella. These include, for example, PCR assay and lateral flow immunoassays. Some assays are for the general detection of all Salmonella spp. Further typing is required after these general detection assays. Other NPIP-approved rapid assays are specific for Salmonella enterica serotype Enteritidis.
Treatment and Control of Pullorum Disease in Poultry
Treatment: not recommended
Control: preventing infection and eliminating positive birds and flocks
Pearls & Pitfalls
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Treatment of flocks with pullorum disease will not alleviate the perpetuation of the carrier state and is not recommended.
Control is based on routine serological testing of breeding stock to assure freedom from infection. Pullorum is a host-adapted Salmonella, and the usual source is other poultry by vertical or horizontal transmission. In addition, management and biosecurity measures should be taken to decrease the introduction of SPullorum from feed, water, wild birds, rodents, insects, or humans. Birds should be purchased from sources free of S Pullorum.
The NPIP outlines the essential components for eradication of S Pullorum.
Key Points
S Pullorum causes high mortality rates in young chickens and turkeys and is transmitted from infected hens (vertical) or horizontally from infected birds or contaminated feed, water, or litter.
Classic lesions include white nodules in the liver, spleen, lungs, heart, gizzard, and intestine and cecal cores.
Confirmation of S Pullorum is through isolation and identification of the organism. Control measures focus on testing and eradication of the disease.
The goal for control of pullorum disease is elimination of the pathogen, particularly from breeding flocks; therefore, treatment is not recommended.
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.
