Case report: Systemic granulomatous disease with vasculitis in a bull due to hairy vetch (Vicia villosa) toxicosis

Abstract

A 5-year-old Angus bull presented for generalized alopecia, thickened pleated skin and profuse malodorous watery diarrhea. This bull, along with 6 other beef bulls, had been grazing in a pasture containing hairy vetch (Vicia villosa) for 5-6 months. Diagnostic samples included blood for CBC and chemistry, skin biopsy and scrapings, fecal sample and liver biopsy. Biopsy of skin revealed a chronic, moderate, perivascular and perifollicular, eosinophilic to histiocytic-lymphocytic dermatitis with moderate acanthosis and hyperkeratosis indicative of an ongoing hypersensitivity reaction. The bull did not respond to treatment and was euthanized due to poor prognosis. At necropsy, disseminated systemic granulomatous disease with variable numbers of multinucleated giant cells and eosinophils was observed in multiple organs indicative of systemic granulomatous disease, along with vasculitis in the kidney, liver, and adrenal gland, indicative that vasculitis is involved in the pathogenesis of the lesions. Viral diseases were ruled out by immunohistochemistry of sections of kidney and by in situ hybridization on kidney sections. CD3, CD20, and CD79a lymphocyte markers immunostaining of sections of kidney revealed predominance of CD3 positive lymphocytes, indicative of predominance of T-cell lymphocytes supporting a type-IV hypersensitivity. The vasculitis observed prompted formulating a list of differential diagnoses for infectious diseases that have evidence of vasculitis, including bovine virus diarrhea virus and malignant catarrhal fever. Vasculitis, although previously described in cases of hairy vetch poisoning, is not observed in every single case of the disease. The remaining bulls were not removed from the pasture and none developed clinical signs.