As long as the exact etiology of jagziekte and of progressive pneumonia remains unknown, it cannot be said that they are identical, although on the basis of the observations detailed above, they certainly appear to be. It is extremely doubtful whether it is possible to distinguish between them. In the localities in which they occur, each is recognized as an infection quite distinct and apart from other better known pneumonias. Predisposing factors which lead to bacterial invasion are presumably of great importance in both. We have no precise information regarding the organisms concerned, but in both diseases, the initial changes are alike and occur in the interalveolar tissue and the subsequent proliferations of epithelium and the pneumonia are of the same character and apparently follow in exactly the same sequence. Finally, in both diseases, there is much fibrosis and the animals inevitably die through depletion of respiratory area and pneumonia.
The view hitherto held, that jagziekte is a disease definitely restricted to the Union of South Africa, is thus rendered improbable. Nor does it appear likely that jagziekte is due to a single specific virus acting primarily upon the epithelial cells of the lungs, which is is likewise a conception widely accepted in South Africa.