Systemic granulomatous disease in cattle in Rio Grande do Sul, Brazil, associated with grazing vetch (Vicia spp)
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Two outbreaks of a disease associated with grazing vetch species (predominantly Vicia villosa and to a lesser extent V. sativa) were observed during August-September 2001, in adult Holstein cows from two farms in southern Brazil. In one of the farms four out of 42 cows (9.5%) and in the other one out of eight cows (12.5%) were affected. Clinical signs included, although not consistently, fever, pruritus, thickening and wrinkling of the skin with multifocal plaques of alopecia, conjunctivitis, nasal serous discharge, loss of weight, dramatic drop in milk yield, and diarrhea. The duration of the clinical disease was approximately two weeks. All clinically affected cows died, one was euthanatized; three were necropsied. In each of these animals there was a pattern of systemic lesions consisting of multifocal to coalescing grey-white soft to moderately firm nodules which infiltrated several organs but were particularly prominent in the myocardium, lymph nodes, spleen, adrenal gland and renal cortex. These lesions resulted in enlargement and disruption of the architecture of the invaded organ. Microscopically the lesions consisted of extensive cellular infiltration composed of variabe proportions of epithelioid macrophages, lymphocytes, plasma cells, multinucleated giant cells and eosinophils. Eosinophils numbers were usually large. This granulomatous infiltration caused degeneration and loss of parenchymal cells of affected organs. Intensity of lesions varied among the three cows and among individual organs. This is the first documented report on a systemic granulomatous disease in cattle associated with grazing vetch in Brazil.
