SIGNALMENT (AFIP #2741081):  5 year old, female Angus-cross cow

HISTORY:  This cow had chronic weight loss and diarrhea for 2 months.  Four herdmates died with similar clinical signs.  At necropsy, the small intestinal mucosa was markedly thickened with prominent corrugated mucosal folds, and the mesenteric lymph nodes were markedly enlarged and firm.

HISTOPATHOLOGIC DESCRIPTION:  Small intestine:  Diffusely and markedly expanding the lamina propria and submucosa up to 5 mm, and replacing and widely separating crypts, are numerous epithelioid macrophages arranged in dense sheets. Macrophages have abundant, finely-granular pale eosinophilic cytoplasm and an eccentric round to oval nucleus with finely-stippled chromatin.  Villi are blunted and fused, and form prominent mucosal rugose folds.  Multifocally, moderate numbers of lymphocytes, plasma cells, eosinophils and rare multinucleated giant cells are admixed with macrophages.  Multifocally, crypt epithelial cells have increased cytoplasmic basophilia, vesicular nuclei, and mildly increased numbers of mitotic figures, and pile up to 5 cell layers deep (regeneration).  Low numbers of lymphocytes are present within the muscular layers and subserosal adventitia.  Diffusely, within the submucosa, tunica muscularis, and serosa, there is increased clear space and mildly ectatic lymphatics (edema).  Diffusely, there is marked fat atrophy within the serosa, which is often lined by hypertrophied (reactive) mesothelium.

Slide B (acid fast): Small intestine:  Diffusely, macrophages contain large numbers of 1 x 2 um acid-fast bacilli.

MORPHOLOGIC DIAGNOSIS:  Small intestine: Enteritis, granulomatous, diffuse, marked, with villus atrophy, edema, and numerous intrahistiocytic acid-fast bacilli, Angus-cross, bovine.

ETIOLOGY: Mycobacterium avium subspecies paratuberculosis (MAP)

ETIOLOGIC DIAGNOSIS: Mycobacterial enteritis

CONDITION: Johne"s disease, paratuberculosis










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