Abstract
The lungs in zwoegerziekte, a chronic pulmonary disease, are greatly increased in weight, do not collapse, and are either pale and dry or mottled with grey consolidation. The initial stage is characterized by peribronchial, perivascular, and solitary lymphoid hyperplasia and cellular infiltration of alveolar septa with consequent thickening. Fibrosis or myofibrosis, thickening of arterial walls, epithelial proliferation of air passages, and alveolar fetalization characterized the end stage.
Pathologically zwoegerziekte, maedi, and progressive pneumonia have predominantly a mesenchymal reaction and belong to a single entity, chronic interstitial pneumonia of sheep. Zwoegerziekte bears close pathologic similarity to ‘la bouhite’ and ‘Graaff-Reinet disease’ but differs from pulmonary adenomatosis. Whether atypical pneumonia, also a type of interstitial pneumonia but different from maedi, occur in The Netherlands and may complicate some cases of zwoegerziekte is not known.