Experimental induction of pneumonia in mice with Bordetella parapertussis isolated from sheep.

The intranasal inoculation of mice with a suspension of ovine isolates of Bordetella parapertussis killed about 11 per cent of animals (four out of 34) between 2 to 3 days post-inoculation and produced a subacute bronchopneumonia morphologically similar to early lesions of naturally occurring ovine chronic non-progressive pneumonia. Pulmonary lesions characterized by alveolar septal congestion and oedema, focal alveolar haemorrhage and intraalveolar and septal infiltration by neutrophils and macrophages were seen in the early stages. Bronchioles often contained an exudate of macrophages, neutrophils and fibrin and later hyperplasia of perivascular and peribronchiolar lymphoid tissue and fibrosis of the interalveolar septa were evident. Electron microscopy revealed extensive degenerative changes in the alveolar epithelium and alveolar macrophages. Pure cultures of B. parapertussis were consistently recovered from infected lungs from 12 h after inoculation to pid 6. Intact organisms and organisms showing varying degrees of degeneration were found free in alveolar spaces or phagocytosed by alveolar macrophages.