Infection and immune responses in chickens exposed to Salmonella typhimurium

The transmission of Salmonella typhimurium among adult chickens maintained in wire-floored cages was examined. Within 6 days, organisms had spread from infected seed chickens to the majority of uninoculated chickens. Initially, organisms were found in the intestinal tract alone, but by day 20, all chickens were infected, and most of these had organisms in the liver, spleen, and intestinal tract. Antibodies to whole bacterial cells and lipopolysaccharide were detected in the serum and bile of all chickens from day 24. Clearance of organisms from the tissues was not apparent until after day 33. Cell-mediated immunity to salmonella antigens was also induced in chickens that naturally acquired the infection. The role of these parameters of immunity in the clearance of organisms is discussed.