Two outbreaks of Xanthium cavanillesii poisoning in feedlot cattle in the counties of Casca and Cachoeira do Sul, Rio Grande do Sul, southern Brazil, are described. The disease occurred on two farms in late April and mid August 1996. On one farm, 17 heifers out of 310 cattle died. On the other, 11 out of 83 yearling calves died. Clinical signs included depression, anorexia, progressive dehydration, sunken eyes, tenesmus and slight rectal prolapse, muscle tremors, incoordination of gait, blindness, aggressivity and recumbency. Blindness was present in the terminal stages prior to death that occurred within 3 to 24 hours after the onset of the clinical signs. Necropsy findings included accentuation of the lobular pattern of the liver with pinpoint hemorrhages on capsular and cut surfaces; perirenal edema, hydropericardium, and translucent and gelatinous edema of the gall bladder wall, mesentery, abomasal ligaments and folds. The feces were scant, dry and formed balls coated by mucus and streaks of clotted blood. There were widespread petechiae, ecchymoses and suffusions. Burs of X. cavanillesii were found mixed with the solid and dried contents of the rumen and reticulum. The main histopathological findings were marked centrilobular coagulative hepatocellular necrosis associated with congestion and hemorrhages, surrounded or not by a narrow rim of markedly swollen and vesicular hepatocytes. The animals were being fed with whole or milled leftovers from soybean crops contaminated with large amounts of burs of X. cavanillesii. Deaths stopped after the feeding with the soybean leftovers was discountinued. The diagnosis was based on epidemiological data, clinical signs, necropsy findings, histological lesions and experimental reproduction of the toxicosis in cattle and sheep. The morphology and pathogenesis of the hepatic lesion and the clinical and pathological aspects of the toxicosis are discussed and compared with other reports of Xanthium spp poisoning and other acute hepatotoxicoses in cattle.
Poisonous plants; plant poisoning; hepatotoxicosis; Xanthium cavanillesii; Asteraceae; diseases of cattle; pathology
