Systemic Granulomatous Disease in Cattle in California Associated with Grazing Hairy Vetch (Vicia Villosa)

in the state of California, and only 2 cases have been reported, possibly because of lack of recognition of the disease. Vetch is not a major component of range and pasture land in the state of California but is abundant on disturbed soil from coastal areas to the Sierra foothills. It has been grown as a seed crop in northwestern California, and in other parts of California it has been used as a green-manure crop and for hay. In the 1950s and 1960s vetch was planted in the Sierra foothills of California by the Soil Conservation Service for soil erosion control. Vetch has become well established, and with increased awareness and recognition of the disease, reports may increase. Systemic granulomatous disease in horses is most likely multifactorial. There may be multiple etiologies with a common pathogenesis. Consumption of vetch may be 1 etiology associated with SGD in horses, as it is in cattle. The organ distribution, the perivascular nature of the inflammatory infiltrate, and the components of the inflammatory infiltrate of both diseases are similar, except for the lack of a prominent eosinophilic component of the granulomatous inflammation seen in the horse in the present case. Eosinophils have been seen in some horses with SGD (L. W. Woods, personal observation). Many cases of SGD occur without known exposure to vetch pasture. Disease in cattle induced by vetch may be the result of a hypersensitivity to 1 or more plant constituents that are absorbed and combine with host constituents to stimulate the inflammatory response. These plant constituents or immunogens in vetch that induce disease may also be present in other forage or organisms.