An investigation of ovine pneumonia in four herds from Central Norway. II. Relation between pathomorphology and presence of micro-organisms.

Sheep lungs obtained at slaughter from 4 herds from Central Norway were subjected to a macroscopical examination. Gross pulmonary findings included normal lungs, fibrous pleurisy, verminous nodules, atelectasis and consolidations of lobular and lobar extensions. A selection of lungs representing the various gross findings was subjected to microbiological and histological examinations. Pleurisy was associated wtih pneumonic consolidations and extension of lesions. Verminous nodules indicative of Muellerius spp. migrations occurred irrespective of gross pulmonary lesions or microbiological findings. A subacute or chronic pneumonia of a mixed proliferative exudative type was demonstrated in consolidated tissue. An association was found between the isolation of Mycoplasma ovipneumoniae and the presence of pneumonic lesions and between the number of organisms and extension of lesions. Histological findings highly indicative of this organism were proliferative changes in the bronchiolar and bronchial epithelium and intrapulmonary lymphoid tissue. The intensity of these changes was correlated to the number of mycoplasma organisms present. Mycoplasma ovipneumoniae is suggested to be of primary etiological significance regarding subacute or chronic pneumonia in lambs at slaughter.