Outbreaks of poisoning by Vernonia rubricaulis in cattle were observed on nine farms, in the state of Mato Grosso do Sul, between September 1999 and May 2001. At least 954 cattle died. Several conditions seemed to be important for the occurrence of the outbreaks: the use of practices that induced sprouting of the plant, including the control of weeds with a crushing device, made with three pieces of rail, or burning or jungle clearing of the paddocks; transportation of cattle from other farms or their change from one paddock to another on the same farm, and high stocking rate. The clinical course varied from 12 to 48 hours. Clinical signs were agressivity or dullness, salivation, blindness, groaning, incoordination, abdominal retraction, dry feces with mucus and blood, dry nose, and recumbency. Lethality was 100%. Main gross lesions were found in the liver. They varied from animal to animal and within the same liver. In some cases, a variable number of focal hemorrhages 1mm up to 25cm in diameter were observed within the yellow liver tissue. Nutmeg appearance was frequently seen. A diffuse yellow liver, occasionally with petechial hemorrhages, was also observed. Hemorrhages were seen also in other tissues. Main histologic lesions were liver necrosis, mainly centrilobular, with severe vacuolation of midzonal and periportal hepatocytes. The gross red areas corresponded to diffuse necrosis, and the yellow areas to diffuse vacuolation of hepatocytes. The poisoning was produced experimentally in three cattle, causing death with 3g of the green sprouting plant per kilogram body weight. Gross and histologic lesions were similar to those observed in spontaneous cases.
Toxic plants; Vernonia rubricaulis; liver necrosis; cattle
