Pyrrolizidine alkaloidosis in Argentinian cattle caused by Senecio selloi.

A herd of 135 Aberdeen Angus cows were grazing on pastures containing abundant Senecio selloi in the eastern region of Buenos Aires Province, Argentina. Some undiagnosed deaths were observed during 1989. In 1990 the death count raised to 38 animals, all of them showing the same clinical signs and gross and histopathological lesions. The time from the start of signs to death varied from 2 to 6 d. The most conspicuous signs were distention of the abdominal cavity and moderate icterus of mucous membranes. At necropsy, large amounts of fluid were in the abdominal cavity, there were lesions in the digestive tract, kidneys and mesenteric lymph nodes, and the liver was enlarged and fibrous. Histopathology showed the hepatic parenchyma replaced by fibrous tissue with marked megalocytosis. The signs and lesions were consistent with those produced by pyrrolizidine alkaloids. An abundance of Senecio selloi resulted in a diagnosis of poisoning from this plant. This is the first report of toxicity due to this plant species in Argentina.