Morphological investigations on the pathology of Dictyocaulus viviparus infections in cattle.

Morphological investigations of lungs obtained from cattle that had been experimentally infected with Dictyocaulus viviparus were carried out using a new fixation technique that excludes post-mortem changes in the samples. Light and electron microscopical investigation showed a substantial loss of ciliated epithelial cells in the bronchi, severely affecting the mucociliary clearance. Bronchiolitis, peribronchiolitis and cell-rich mucus caused bronchial atelectasis and consolidation of the related alveoli. Interlobular septa completely separated diseased from normal tissue. Clara cells contained abundant intraplasmatic glycogen. Alveolary walls were thickened and showed cellular infiltration, loss of functional epithelial cells and hyperplasia of alveolar type II cells. Increased connective tissue indicated an irreversible chronic decline in lung performance. Lung eosinophilia and the cytotoxic abilities of eosinophils are discussed as a cause of the changes in lung tissue after infection with D. viviparus.