Observation of Apoptosis in Calves Experimentally Infected With Pasteurella multocida Serotype B:2

Abstract

Calves infected intranasally with 3.0 x 10 10 Pasteurella multocida serotype B:2 following dexamethasone treatment died acutely between 24 to 48 hours. All infected calves showed severe swelling of epithelial cells of the nasal mucosa, trachea and lung. Some endothelial cells of the capillary of nasal mucosa, trachea and lung showed condensation of the cytoplasm, chromatin margination, and vesicular surface. Bacteria were found in close contact with endothelial cell membrane. Some of the neutrophils were undergoing apoptosis with perinuclear chromatin aggregation and cytoplasmic vacuolization. Detached apoptotic endothelial cells were also seen in the lumen of the blood vessels. These findings suggest that apoptosis in infected neutrophils and endothelial cells may contribute to the pathogenesis of haemorrhagic septicaemia.