Atypical bovine interstitial pneumonia in a semi-intensive beef cattle system

The aim of the present study was to describe an outbreak of atypical interstitial pneumonia affecting 15 Angus cattle aged 7-30 months in the south of Rio Grande do Sul. The clinical course of the disease was approximately 1-3 days. The cattle were kept in the native field and had received feed containing the remains of wafers from a food factory before the outbreak. Clinical signs included dyspnea and abdominal breathing, with a clinical evolution period of up to 3 days. Nine animals presented apathy and respiratory difficulty and died within 24h, while three animals exhibited a clinical evolution period of 36-48h. Three other animals died without any clinical signs. The main macroscopic lesions were observed in the lungs, which did not collapse at the opening of the thoracic cavity and showed a rubbery consistency. On the cut surface, the organs were firm and dark red, with marked distension of the interlobular septa due to edema. Histopathological analysis revealed thickening of the interlobular pulmonary septa; interstitial edema and emphysema; mild mononuclear cell, eosinophil, and neutrophil infiltration; areas of type II pneumocyte proliferation, and thickening of the alveolar walls. Fibrin was observed in the alveolar lumen with the formation of hyaline membranes. On the basis of macroscopic and histological examinations and epidemiological data, a final diagnosis of atypical interstitial pneumonia was made. Although, the cause of the disease has not been identified, it is believed that the bran wafer meal contained ingredients that were not suitable for animals, consequently triggering the disease. RESUMO: Descreve-se um surto de pneumonia intersticial atípica diagnosticado no Sul do Rio Grande do Sul, afetando 15 bovinos da raça Angus, entre 7 e 30 meses de idade, de um total de 400 animais. Os bovinos estavam em campo nativo e recebiam farelo de bolacha proveniente de uma fábrica de produtos alimentícios. Os sinais clínicos caracterizaram-se por dispneia e respiração abdominal. Nove animais apresentaram apatia e dificuldade respiratória morrendo em 24 horas, em três bovinos a evolução clínica foi de 36 a 48 horas e outros três morreram sem observação de qualquer sinal clínico. As principais lesões macroscópicas foram observadas nos pulmões, que não colapsavam na abertura da cavidade torácica e apresentavam consistência elástica. Na superfície de corte o órgão era firme e vermelho escuro com acentuada distensão dos septos interlobares e interlobu