Pullorum-Typhoid disease historically caused approximately what mortality rate in poultry?

• A. 80%
• B. 50%
• C. 20%
• D. 5%

Answer: (B)

Pullorum-Typhoid disease causes septicemia in very young poultry, so mortality in newborn chicks is extremely high. The infection is often transmitted from infected breeder hens to their eggs, so chicks hatch already infected and succumb quickly. In historical outbreaks where no eradication or vaccination measures were in place, about half of the affected chicks would die, making around fifty percent the typical mortality level cited. This high loss reflects the severe impact of the disease on the youngest birds, before they can mount an effective immune response. Control programs that tested breeders, culled positive birds, and improved hatchery sanitation dramatically reduced losses, but the historical figure commonly cited is roughly fifty percent.