A sequential light microscopic study of the pulmonary lesions in porcine dermatosis vegetans

The sequential pulmonary changes in dermatosis vegetans were studied in pigs aged one, seven, 14, 17, 21 and 28 days, and two and a half, four and 12 months. At one day old the lung tissues appeared normal. At seven days old there was a moderate infiltration of mononuclear inflammatory cells in the alveolar structures, and proliferation of type II pneumocytes was also observed. At 14 and 17 days old the alveolar structures were intensely infiltrated with mononuclear inflammatory cells. At 21 days old, loosely arranged epithelioid and multinucleate giant cell granulomas appeared, and there was a proliferation of alveolar epithelial cells. By four and 12 months old the inflammatory changes diminished, and small granulomas and moderate alveolar fibrosis were present. The initial lesions were characterised by an alveolitis, developing into loosely arranged granulomas by four months old, and persisting to the age of 12 months. These observations suggest that the interpretation of the lung changes and the disease in general should be revised.