A previous investigation demonstrated that infusion of an
antipyretic drug into the preoptic anterior hypothalamus (PO/AH) of rabbits reduced the
fever usually seen during the initial stages of
infection. This was followed by an increased
fever and an increased mortality rate [32]. The work reported here investigated the hypothesis that the increased mortality was the result of decreased killing and/or increased multiplication of bacteria during the initial, attenuated phase of the febrile course in the
antipyretic-treated rabbits. Rabbits were injected intravenously with Pasteurella multocida and either
sodium salicylate or a control
solution was infused directly into the PO/AH. Infusion of
sodium salicylate reduced the mean
fever 4 hours after injection of bacteria from 2.07 +/- 0.28 degrees C (S.E.M.) to 0.62 +/- 0.43 degrees C. Rabbits with reduced
fevers had decreased blood leucocyte counts and greater numbers of bacteria in lung and liver samples. No differences were seen in reticuloendothelial clearance of
carbon, hematocrit, or intracellular viability of bacteria when
antipyretics were administered. This increase in bacterial numbers corresponds well to the increased mortality found in previous studies in animals with reduced
fevers.