Chicken typhus, Pullorum disease
Salmonella gallinarum, Salmonella pullorum
Chicken typhus and pullorum disease, respectively, are poultry diseases caused by bacteria of the species Salmonella(Salmonella gallinarum causes chicken typhus, Salmonella pull orum causes pullorum disease). These Salmonella show high specificity for poultry and waterfowl and usually do not cause symptoms in mammals. Infection with S. gallinarum or S. pullorum can cause high losses in chickens, turkeys, and other avian species.
The pathogens are introduced into flocks by infected animals and animate and inanimate vectors (feed, water, objects such as transport crates, etc.). The transmission of the pathogens from infected parents via the hatching egg is of great importance for the spread of the infection and leads to white chick dysentery in chicks (pullorum disease).
Decreased hatching rates, hatching of weak chicks, chalky white diarrhea with a mortality of more than 50% and movement disorders, joint inflammations, lameness, cramps, weeping, poor plumage in surviving chicks. Older birds, which may be latently infected, show nonspecific symptomatology such as laying performance decline.
Situation in Austria
Consistent control has reduced the incidence of chicken typhus and pullorum in Austria, and only isolated cases have occurred in recent years. The occurrence of Salmonella gallinarum and/or Salmonella pullorum in poultry is notifiable in Austria according to the Poultry Hygiene Ordinance 2007.
Chicken typhus and pullorum disease are caused by Salmonella, Gram-negative, as opposed to zoonotic Salmonella non-motile rod bacteria. Susceptible birds are mainly poultry, but infections with high losses have been described in many different bird species (turkey, guinea fowl, quail, pheasant, sparrow, and parrots). In pullorum disease, caused by Salmonella gallinarum biovar pullorum, vertical transmission from infected parents to hatching eggs results in reduced hatching rates and hatching of weakly alive chicks. Yolk sac regression is delayed, and acute septicemic infections occur in chicks up to 3 to 6 weeks of age. Increased urate excretion led to the disease name "white chick dysentery" with high mortality of >50%. Chicken typhus(Salmonella gallinarum biovar gallinarum) causes nonspecific symptoms in older chickens, such as decreased laying performance, decreased feed intake, and pale combs. Pathology shows enlarged liver and spleen with pale necrotic foci, possibly with fibrinous deposits on the seroses. The infection may be peracute in laying hens.
Serological tests are suitable for herd testing, but they may cross-react with other salmonellae. Bacteriological isolation and identification of S. Gallinarum and S. Pullorum from organ samples (liver, spleen, yolk sac, caecum) are necessary for definitive clarification. Bacteriological examination is performed by enrichment or organ direct smears and incubation of the culture media at 37 °C or 42 °C for 24-48 hours. Differentiation between the two Salmonella biovars is done by testing for fermentation of ornithine(S. Gallinarum negative, S. Pullorum positive).
Last updated: 10.10.2023