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Histological examinations were carried out on the lungs of calves in two groups in order to detect pathomorphological changes. The calves from the 1st group had parainfluenza and the 2nd group included the animals with an acute course of catarrhal purulent bronchopneumonia showing clinical signs of chronic and acute pulmonary pathology. Histological methods were used in the work. The established pathomorphological changes in the lungs of calves of the 1st group in the form of chronic interstitial bronchopneumonia, accompanied by compensatory chronic alveolar emphysema, the formation of multinucleated symplata and multicellular syncytiae from alveolar epithelium, and also mixed cytopathic forms of respiratory epithelium - symplasts-syncytium are characteristic cytological signs of chronic parainfluenza infection. Local thickening of the bronchial walls due to proliferation of multilobular epithelium and infiltration of the submucosa by lymphoid cells with narrowing of the lumen profiles also confirms the parainfluenza etiology of the changes in the lungs. The observed manifestations of bronchopneumonia were most pronounced in the most ventilated cardiac and diaphragmatic lobes of the lungs of sick calves. The chronic inflammatory process in the lungs in parainfluenza was complicated by fibrinous pleurisy as well as peri- and endocarditis, myocardiodystrophy with the abnormal structure of cardiomyocytes, and atypical heart cells. In the pulmonary lymph nodes of parainfluenza calves, moderately marked hyperplasia of lymphoid tissue cells with the presence of secondary lymph nodes, some of which had a pronounced structure of dark cell periphery and a wide cell-saturated germinative zone was observed. In the 2nd group of calves with acute catarrhal purulent bronchopneumonia, the above cytopathic changes in the airways and respiratory region of the lungs could not be detected. Pathological changes in the lungs were predominantly exudative in nature and were represented by serous alveolitis, catarrhal purulent bronchopneumonia with the involvement of the anterior and cardiac lobes of the organ. The short course of the disease was accompanied by weak lymphoid cell proliferation in the pulmonary lymph nodes.