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

portuguesDescreve-se um surto de pneumonia intersticial atipica diagnosticado no Sul do Rio Grande do Sul, afetando 15 bovinos da raca 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 fabrica de produtos alimenticios. Os sinais clinicos caracterizaram-se por dispneia e respiracao abdominal. Nove animais apresentaram apatia e dificuldade respiratoria morrendo em 24 horas, em tres bovinos a evolucao clinica foi de 36 a 48 horas e outros tres morreram sem observacao de qualquer sinal clinico. As principais lesoes macroscopicas foram observadas nos pulmoes, que nao colapsavam na abertura da cavidade toracica e apresentavam consistencia elastica. Na superficie de corte o orgao era firme e vermelho escuro com acentuada distensao dos septos interlobares e interlobulares por edema. Histologicamente, havia espessamento dos septos interlobulares pulmonares, edema e enfisema intersticial, infiltrado inflamatorio discreto de celulas mononucleares, eosinofilos e neutrofilos, areas de proliferacao de pneumocitos tipo II e espessamento das paredes alveolares. Havia fibrina na luz alveolar e formacao de membranas hialinas. As lesoes macroscopicas e histologicas, associadas aos dados epidemiologicos, permitiram o diagnostico de pneumonia intersticial atipica. Apesar de nao ter sido identificada a causa da enfermidade acredita-se que o farelo de bolacha, com ingredientes nao adequados a alimentacao animal e em forma de farelo, possa ter desencadeado a doenca. Palavra-chave: edema e enfisema pulmonar; disturbio respiratorio; bovinos; hipersensibilidade; pneumonia intersticial EnglishThe 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. Key words: pulmonary edema; emphysema; respiratory disorder; cattle; hypersensitivity; interstitial pneumonia