JPC SYSTEMIC PATHOLOGY
SIGNALMENT (JPC #1803541): Seven-year-old Angus cow
HISTORY: Three of four ill animals in a herd of forty died after an illness of about two weeks. Clinical signs in this cow included bloody diarrhea. Other ill animals were constipated and several had a papular or scaly dermatitis.
HISTOPATHOLOGIC DESCRIPTION: Kidney: Multifocally scattered throughout the cortex and extending into the medulla, are multifocal-coalescing aggregates of macrophages, eosinophils, multinucleated giant cell macrophages (foreign body and Langhans type), lymphocytes and plasma cells admixed with multifocal minimal hemorrhage, fibrin and edema, which expand the interstitium and separate, surround, and replace medullary and cortical tubules and glomeruli. Tubules are mildly to moderately ectatic, contain sloughed tubular epithelium, variable amounts of proteinaceous fluid or necrotic celluar debris. Multifocally, tubular epithelium is either swollen with vacuolated cytoplasm (degeneration), shrunken with pyknosis and hypereosinophilic cytoplasm (necrosis) or with basophilic cytoplasm and crowded and vesiculate nuclei (regeneration). Multifocally, there is mild parietal epithelial hypertrophy that is occasionally attached to the glomerular tuft (synechia) with occasional ectatic uriniferous spaces containing protein.
MORPHOLOGIC DIAGNOSIS: Kidney: Nephritis, interstitial, granulomatous and eosinophilic, multifocal to coalescing, moderate, with tubular degeneration, necrosis, and regeneration, Angus, bovine.
ETIOLOGIC DIAGNOSIS: Hairy vetch (toxic) nephritis
CAUSE: Hairy Vetch (Vicia villosa Roth) toxicity
- Hairy vetch is a legume related genetically to the lupines
- Low morbidity and high mortality; death is usually 10-20 days after the onset of illness
- Causes a multisystemic syndrome in cattle and horses
- Granulomatous and eosinophilic inflammation in cattle
- Predominantly granulomatous and infrequent eosinophilic inflammation in horses
- Three syndromes in cattle:
- Dermatitis, conjunctivitis, diarrhea and granulomatous inflammation of many organs (most common form; immunotoxic syndrome)
- Acute neurological disease/seizures and hemolysis after consuming seeds (unrelated to immunotoxic syndrome)
- Swelling of upper body with herpetiform eruptions of oral mucous membranes, respiratory distress and death
- Toxicity of vetch seeds due to prussic acid (hydrogen cyanide); binds metallic cofactor in metalloenzymes; also can cause inhibition of oxidative phosphorylation in acute intoxication (cytochrome C inhibition, ruminants most susceptible, bright red mucous membranes, sorghum and sudangrass); chronic toxicity leads to white matter demyelination
- The pathogenesis of granulomatous inflammation is unclear; suspect immunotoxin (lectin); prior exposure may be required
- Ingestion of vetch > antigen formation in form of hapten or complete antigen that sensitizes lymphocytes > evokes cell-mediated immune response upon repeat exposure
TYPICAL CLINICAL FINDINGS:
- Pruritic dermatitis, wasting, diarrhea (possibly bloody)
- Papules and crusts initially on udder, teats, escutcheon and neck; progresses to trunk, face and limbs
- Lymphocytosis and hyperproteinemia
TYPICAL GROSS FINDINGS:
- Yellow nodular infiltrates disrupt architecture of wide range of organs – most severe in myocardium, kidney, lymph nodes, thyroid and adrenal glands
- Kidney may have radially oriented cortical infiltrates that follow the vasculature
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Granulomatous and eosinophilic inflammation in multiple organs is unique and often diagnostic when coupled with history of exposure to hairy vetch
- Infiltration by macrophages, lymphocytes, plasma cells, multinucleated giant cell macrophages, and eosinophils (in cow) in all affected organs
- Skin: In addition to inflammation, there is marked hyperkeratosis and dermal and epidermal edema
- Histologic lesions are similar to those seen with citrus pulp toxicity, citrinin (a mycotoxin in feed) and 1,1-diureidoisobutane (DUIB) (a protein feed substitute)
- Sarcocystis: Granulomatous and eosinophilic myocarditis with cyst rupture
- Horse: Similar to cattle with lymphadenomegaly and dependent edema; infrequent eosinophils and lack of cardiac involvement
- Horses develop a similar condition with no history of vetch exposure: “vetch-like disease”
- Referred to as: “idiopathic granulomatous disease involving the skin”; “systemic granulomatous disease”; “generalized granulomatous disease”; or equine sarcoidosis”
- Variable organ involvement
- Skin lesions: scaling, crusting, facial and limb alopecia, progression to generalized exfoliative dermatitis
- Deep perifollicular nodules of granulomatous inflammation
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