Ocorrência de pneumonia associada à infecção por Mannheimia haemolytica em ovinos de Minas Gerais

Abstract

This paper describes an outbreak of pneumonia in a sheep herd in the central region of Minas Gerais, Brazil. Clinically, the animals presented apathy, exhibited respiratory difficulty during 2 to 3 days or sudden death. The animals were not medicated and found dead. Grossly, the pulmonary findings were similar in all sheep. The pulmonary cranial lobes and the ventral portion of caudal lobes were consolidated and purulent exsudate streamed out of the airways. In the parenchyma of the cranial lobes there were white slightly prominent multifocal to coalescent areas with 0.2 to 0.5cm in diameter intercalated with dark red areas. Consolidated lesions occupied 70 to 80% of the lungs. Fibrinous pleuritis was observed in sheep 1, 2 and 3. Microscopically, the findings were fibrinopurulent bronchopneumonia with intense hyperemia, areas with intra-alveolar hemorrhage and thickening of interlobular septa with numerous neutrophils, cellular rests and scattering fibrin. Multifocal areas with liquefaction necrosis containing numerous bacterial colonies were observed in sheep 1, 2 and 3. In the cranial lobes of these sheep, there were areas with degenerated neutrophils forming clusters of basophilic cells with alongated nuclei ("oat cells") associated with bacterial colonies. The histological findings were characteristic of pneumonia caused by Mannheimia (M.) haemolytica. Samples of the cranial lobes were sent for bacterial culture, and M. haemolytica was isolated and identified in all animals. This is the first report correlating pathological findings and the isolation of M. haemolytica as cause of bronchopneumonia in sheep in the country.