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By Dr. Ibne Ali, IMN PyrophosUpdated October 20269 min read
Pullorum Disease (Hindi)

A complete explanation of Pullorum Disease along with its treatment

Pullorum Disease (PD) and Fowl Typhoid (FT) are septicemic bacterial diseases of chickens and turkeys. However, other birds such as quails, pheasants, ducks, peacocks and guinea fowls can also be susceptible to it. Pullorum disease has been recognised since 1899. It is a common disease in many parts of the world, where it causes heavy economic losses. However, the disease has been eliminated from commercial poultry in the United States, Canada, Australia and Western Europe.

Cause of the Disease and Epidemiology (Etiology & Epidemiology)

Pullorum disease is caused by the bacterium Salmonella Pullorum. These are placed in a single species called Salmonella enterica serovar Gallinarum-pullorum, which is highly adapted to poultry. These bacteria are Gram-negative, non-motile, slender rods and facultative anaerobic. A specific biochemical difference between S. Pullorum and S. Gallinarum is that S. Pullorum rapidly decarboxylates ornithine while S. Gallinarum does not.

Chickens are the natural host for S. Pullorum. However, outbreaks of PD have also been described in turkeys, guinea fowl, quails, pheasants, sparrows, parrots and other birds.

PD can spread in many ways, such as horizontal transmission through contaminated feed, water, droppings and other things. But egg transmission, through contamination of the ovum after ovulation, is the most important route of spread. Infected adult hens become carriers and can pass the infection to their embryos through the egg (vertically).

The disease is widely distributed around the world, but it has been eradicated from commercial poultry in many developed countries such as Western Europe, the United States, Canada, Australia and Japan. In developing countries, such as Latin America, the Middle East, the Indian subcontinent, Africa and perhaps other parts of the world, S. pullorum infections are common and pullorum disease remains one of the major threats to poultry producers.

The severity of the disease varies depending on factors such as age, stress on the bird, management, nutritional status, the route and dose of exposure, and the stress of other diseases in the flock.

Pathogenesis

The pathogenicity of Salmonella pullorum depends on its invasive ability to survive and multiply inside cells, especially inside macrophages. The bacteria are usually taken in through the mouth and first pass through the acidic environment of the proventriculus so that they can reach the small intestine. After invading through the intestinal mucosa, cecum, tonsils and the bursa of Fabricius, the organisms are taken up by macrophages and finally enter the blood, which is called bacteremia. From the blood, the bacteria spread to various organs such as the liver, lung, spleen, kidney, various parts of the hen’s reproductive tract, the testes of the male and other tissues, causing pathological lesions. It has also been confirmed that the bacteria invade the ovary and egg follicles, and this infection persists in the ovary and egg follicles and is passed into the eggs laid and then into the chicks hatched from those eggs.

Clinical Signs

Pullorum disease usually affects chicks before 2 to 3 weeks of age. Clinical signs in chicks and poults include:

  • Anorexia (loss of appetite)
  • Huddling together
  • Droopy wings
  • Dehydration
  • Diarrhea
  • Ruffled feathers
  • Weakness
  • White material caked around the vent (white-caked vents / pasting of the vent feathers)
  • Difficulty in breathing (dyspnea)
  • Blindness
  • Swelling of the hock joints
  • Excessive numbers of dead-in-shell chicks and the highest mortality after hatching

The highest mortality is usually seen in birds of 2 to 3 weeks of age, and it can reach up to 100%.

In growing and mature birds, clinical signs may not be clear in some cases. Signs that may be seen include reduced feed intake, a drooping appearance, ruffled feathers, and pale, shrunken combs. A drop in egg production, fertility and hatchability may also be seen.

Lesions

In acute cases, gross lesions may be few. In acute cases, the liver, spleen and kidneys may be seen enlarged and congested.

  • The liver may have white foci of necrosis.
  • The spleen may be enlarged and mottled white.
  • The contents of the yolk sac may be coagulated, with fibrinous exudate on the pericardium, the capsule of the liver and the peritoneum.
  • White or light yellow nodules may be present in the epicardium and myocardium. Large sterile necrotic lesions in the myocardium may be seen in chronic cases.
  • Similar small nodules may also be present in the gizzard, pancreas, lung, muscle and sometimes in the wall of the cecum.
  • There may be caseous cores in the lumen of the cecum.

Other lesions may include swelling of the joints with thick fluid in the synovium, and exudate in the anterior chamber of the eye.

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In adult hens, lesions may be minimal, such as small nodular regressing ovarian follicles. But the most prominent lesions are a few to many misshapen and discoloured nodular ovarian follicles, which may be attached to the ovary by a long stalk. The oviduct often has caseous exudate in the lumen. Fibrinous exudate may also be seen on the peritoneum and the capsule of the liver. In males, the testes may have white foci or nodules.

Histologically, in acute cases in young chicks and poults, there is coagulative necrosis of hepatocytes with infiltration of heterophils, mixed with fibrin, fibrinosuppurative inflammation of the yolk sac, pericardium, peritoneum and lungs, and caseous cores in the ceca. Nodules in the ovaries of adults are usually made up of pyogranulomatous inflammation associated with many bacteria.

Diagnosis

A preliminary diagnosis of PD can be made on the basis of flock history, clinical signs, mortality and lesions.

For a confirmed diagnosis, isolation and identification of S. Pullorum is necessary. Organs such as the liver, spleen, yolk sac and ceca are the preferred organs for culture. In mature birds, lesions are present in the reproductive organs and in the oviduct, ovarian follicles and testes, and these can be cultured. These organs and other organs of chicks can be cultured directly on veal infusion and brilliant green agar plates and incubated at 37°C for 48 hours.

Various serological tests can be done, such as the microscopic tube agglutination test, the rapid serum test, the stained antigen whole blood test, and the microagglutination test using tetrazolium-stained antigen. ELISA is also available and can be used to screen large numbers of blood samples. However, the antigens used in these tests will cross-react with serum from birds infected with other Salmonella, especially Salmonella Enteritidis. Serological tests are satisfactory for establishing the presence of infection in a flock and estimating it.

Biochemical tests are used to differentiate S. Pullorum from S. Gallinarum and from other common pathogens. Salmonella Pullorum ferments glucose and mannitol with gas, while S. Gallinarum does so without gas.

Differential Diagnosis

The signs and lesions of the disease produced by Salmonella pullorum (pullorum disease) and Salmonella gallinarum (fowl typhoid) are clearly indistinguishable. These bacteria are also very similar in their antigenic and biochemical properties.

Public Health Importance

Although Salmonella typhimurium and Salmonella enteritidis are the most common agents of foodborne illness in humans, PD also has public health importance. The disease can spread through meat and eggs. Salmonella pullorum sometimes causes acute, self-limiting enteritis in people who eat heavily contaminated food.

Economic Importance

Salmonella infection is one of the most important global poultry diseases in avian species because of its heavy economic impact, worldwide distribution and the difficulty of controlling the disease. S. pullorum is a main cause of considerable economic importance in the poultry industry, especially in developing countries. The disease can not only cause high mortality rates in young chicks, which can reach 100%, but it also persists for a long time in the spleen and reproductive tract, leading to infection of the eggs or offspring. Economic losses include reduced production (eggs and chicks), condemnation of affected carcasses and the cost of medicines. Elimination of carrier parent flocks and growing birds, and their replacement with new birds, also causes significant economic loss. Exportable eggs and poultry meat must be free from Salmonella, which has a big impact on the country’s currency earnings.

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Treatment & Control

Every possible effort should be made to eliminate PD and FT, and treatment should be the last option. Various sulfonamides, followed by nitrofurans and other antibiotics, have been found effective in reducing mortality from PD and FT. Various other antibiotics such as furaltodone, furazolidone, chloramphenicol, biomycin, apramycin, gentamicin and chlorotetracycline have been used to control and treat PD and FT. However, the use of chloramphenicol for treating poultry is illegal in many countries. Resistance to some antibiotics has also been reported.

Although antibiotic treatment helps reduce mortality, treated chickens remain carriers. Therefore, treatment of Salmonella pullorum is neither possible nor desirable. Prevention is a better approach than treatment, because recovered birds tend to become carriers.

Successful control programmes can be achieved by developing routine serological tests and a slaughter policy, along with good hygiene and management.

The basic requirements for prevention are:

  • Establishing breeding flocks free from PD and FT.
  • Hatching and rearing the offspring in conditions that prevent direct or indirect contact with infected chickens or turkeys.
  • Bringing in eggs only from flocks that are free from PD and FT.
  • Routine serological testing and elimination of carriers.
  • Keeping chicks and poults in an environment that can be cleaned and sanitised.
  • Salmonella-free feed ingredients and a sound biosecurity program.

In countries where there are no eradication programmes, various vaccines have been used to protect birds against fowl typhoid, such as the 9R strain, outer membrane proteins, mutant strains of S. Gallinarum, and virulence plasmid cured derivatives of S. Gallinarum. Live, attenuated vaccines are more effective than inactivated vaccines because they stimulate both cellular and humoral immunity. The S. Gallinarum 9R vaccine gives good protection against fowl typhoid. It is also protective against the closely related S. Enteritidis.

Competitive exclusion is also a control measure. Since adult birds are much more resistant to colonization as a result of their complex, mature intestinal flora, giving newly hatched chicks commercially available cultures of adult intestinal flora within 24 hours of hatching provides a high level of protection against Salmonella colonization.

Some chicken breeds are more resistant to systemic salmonellosis. Several loci/genes contribute to genetic resistance.

Problem in your flock? Send photos of the birds and droppings on WhatsApp for a first opinion from Dr. Ibne Ali.

WhatsApp: 98715 84101

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