The disease was recognized in the early 1900's as causing severe losses in hatchery infected chicks, restricting the growth of the poultry industry. Diagnostic tests were developed by the 1930's that lead to development of national eradication programs in a number of countries. The disease is almost non-existent in commercial poultry flocks in Canada and the U.S.A., but may persist in backyard flocks. It remains an important disease in developing countries. The organism can persist outside the body for many months.
Infected hens pass the bacteria through their ovaries to the eggs.
Surviving chicks may appear weak and drowsy at 4-5 days of age, with white pasty diarrhea around the vent. Respiratory signs may occur, and losses peak at 2-3 weeks of age. Surviving birds may show no signs, but may be carriers. Reacting birds are culled, and bacterial cultures used to confirm the diagnosis. Thorough cleaning and fumigation of incubators between hatches will eliminate carryover of S. pullorum or other pathogenic bacteria, and fluff sampling can be used to monitor of bacterial presence.