September 2017



Signalment (JPC #1947581):  2‑year‑old mixed breed steer

HISTORY:  This steer was persistently infected with bovine viral diarrhea virus (BVDV). It subsequently became dyspneic and developed diarrhea, dehydration, and anorexia.

HISTOPATHOLOGIC DESCRIPTION:  Lung:  Multifocally, affecting approximately 70% of the lung, alveolar spaces are variably filled with numerous viable and degenerate neutrophils that occasionally have streaming hyperchromatic to smudgy nuclei (oat cells), fewer macrophages, abundant eosinophilic cellular and karyorrhectic debris (necrosis), hemorrhage, fibrin, and edema.  Multifocally bronchiolar lumina are variably filled with an exudate composed of numerous viable and degenerate neutrophils, sloughed/necrotic epithelial cells, foamy macrophages with phagocytized debris, fibrin and hemorrhage. Bronchiolar epithelium is occasionally hypertrophic and hyperplastic, piling up to 3 layers thick. Alveolar septa are thickened up to 5 times normal by similar infiltrate with occasional type II pneumocyte hyperplasia.  In severely affected areas, alveolar septa are fragmented and discontinuous (necrotic).  Diffusely, interlobular septa and the pleura are expanded five to ten times normal by dilated lymphatics (edema), polymerized fibrin, hemorrhage,  and scattered macrophages, lymphocytes, plasma cell and neutrophils.  Multifocally vessels are lined by hypertrophied (reactive) endothelium, with marked perivascular edema.

MORPHOLOGIC DIAGNOSIS:  Lung:  Bronchopneumonia, fibrinosuppurative and necrotizing, multifocal, marked, with oat cell formation, mixed breed, bovine.

ETIOLOGIC DIAGNOSIS:  Pneumonic mannheimiosis

CAUSE:  Mannheimia haemolytica

CONDITION:  Shipping fever; bovine respiratory disease complex (BRDC)











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