Blood gas stability and hematological changes in experimentally-induced acute porcine pleuropneumonia

Blood gas and hematological responses to acute, mild Actinobacillus pleuropneumoniae infection of growing pigs was studied. Six pigs (average weight 10.1 kg) were experimentally infected intranasally with A. pleuropneumoniae serotype 5. Four pigs served as controls. Rectal temperatures and arterial blood for gas analysis and hematology were taken at 0, 8, 16, 24, 48 and 72 h postinfection. All infected pigs became febrile showing clinical signs typical of mild to moderate porcine pleuropneumonia; controls remained asymptomatic. Neutrophilia with bands and lymphopenia were observed only in infected pigs. Arterial partial pressures of O2 and CO2, and pH did not change in infected pigs. All pigs were killed after 72 h, and lungs were examined and cultured. Gross and microscopic lesions consistent with porcine pleuropneumonia were seen in 3/6 and 5/6 infected lungs, respectively. Control lungs were grossly normal with no histological evidence of pleuropneumonia. We conclude that in mild, acute porcine pleuropneumonia as established experimentally, a leukogram typical of acute inflammation and stress is seen; however, hypoxemia and alveolar hypoventilation are not features of this form of the disease.