Body temperature responses of Pekin ducks (Anas platyrhynchos domesticus) exposed to different pathogens.

Poultry, like mammals and other birds, develop fever when exposed to compounds from gram-negative bacteria. Mammals also develop fever when exposed to the constituents of viruses or gram-positive bacteria, and the fevers stimulated by these different pathogenic classes have discrete characteristics. It is not known whether birds develop fever when infected by viruses or gram-positive bacteria. Therefore, we injected Pekin ducks with muramyl dipeptide, the cell walls of heat-killed Staphylococcus aureus, or the viral mimic polyinosinic:polycytidylic acid and monitored their body temperature (T(b)). For comparative purposes we also injected a group of ducks with lipopolysaccharide, the only known pyrogen in birds. We then compared the T(b) invoked by each injection with the T(b) after an injection of saline. Muramyl dipeptide did not affect T(b). The cell walls of heat-killed S. aureus invoked long-lasting, dose-dependent fevers with relatively low magnitudes. Polyinosinic:polycytidylic acid invoked dose-dependent fevers with high febrile peaks. Fever is a well-known clinical sign of infection in mammals, and the results of this study indicate that the pattern of increase in T(b) could serve as an indicator for diverse pathogenic diseases in birds.