The Pathology of Pneumonia in Young Lambs Inoculated with Bedsonia

Abstract

Neonatal lambs were inoculated intratracheally with a strain of Bedsonia (Chlamydia) isolated from a case of ovine atypical pneumonia and were examined 3, 5, 9 and 12 days after inoculation. Clinical signs included a marked rise in temperature, dyspnoea and anorexia. One lamb died 5 days after inoculation. Macroscopic lesions of pneumonia were present in each of the Bedsonia-inoculated lambs. In lambs killed 3 and 5 days after inoculation the histological lung lesions were characterized by foci of necrosis and a sero-cellular exudate in alveoli and bronchioles. The principal lesions in lambs killed 9 and 12 days after inoculation were hyperplasia of the bronchiolar epithelium, pseudo-epithelialization and epithelialization of alveoli and infiltration of the interalveolar septa by macrophages and lymphocytes. Elementary bodies were demonstrated in cryostat sections of lung from each of the infected lambs and Bedsonia organisms were recovered from their lungs. Two control lambs inoculated with Bedsonia-free yolk sac suspension and killed 4 and 9 days later remained healthy. No macroscopic or histological lesions of pneumonia were observed, nor were elementary bodies demonstrated or Bedsonia recovered from their lungs.