December 2007

Case A

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Cow with a history of weight loss, lethargy and inappetence.

Example histopathological description

This is a pyramidal section of kidney from capsule to pelvis with a large focus of coagulative necrosis in the medulla, extending to the pelvis. This is delineated by a cell infiltrate. The remainder of the kidney, particularly the cortex, has a moderate, diffuse cell infiltrate of the interstitium and tubules are dilated, with many containing proteinaceous fluid or cell debris. The necrotic focus is surrounded by an inner layer of neutrophils and eosinophils, followed by an outer layer of lymphocytes, plasma cells, some multinucleated giant cells and fibrosis. At the edge of the large necrotic foci there are multifocal small eosinophilic granulomas. In both these and the large necrotic foci there are scattered fungal hyphae. The hyphae are hyaline, 2-10 µm in diameter, irregularly septate, thin walled, often folded and irregularly branching, suggesting they are a Zygomycete. The remainder of the kidney has a moderate interstitial cell infiltrate of lymphocytes and plasma cells with fibrosis.

Morphological diagnosis

1. Pyelonephritis, eosinophilic, granulomatous and necrotising, chronic, multifocal, severe, with intralesional fungal hyphae.

2. Nephritis, interstitial and lymphoplasmacytic, chronic, diffuse, moderate.

Aetiological diagnosis

Mycotic pyelonephritis, probably caused by a Zygomycete

Case B

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Broiler chickens with a history of respiratory signs.

Example histopathological description

This slide contains a longitudinal section of larynx and a transverse section of trachea. Both have mucosal thickening due to epithelial hyperplasia, vascular congestion and cell infiltration of the submucosa. The cell infiltrate is predominantly lymphocytic and plasmacytic, with granulocyte exocytosis across the epithelium and a mild exudate of granulocytes and mucus on the mucosal surface. The epithelial cells have loss and clumping of cilia and numerous small protozoa (3-7µm diameter) are on or within the epithelial surface. There are foci of mild squamous metaplasia in the mucosal epithelium.

Morphological Diagnosis

Laryngotracheitis, lymphoplasmacytic and hyperplastic, subacute, diffuse, moderate, with intralesionalCryptosporidia sp.

Aetiological Diagnosis

Respiratory cryptosporidiosis