Hepatotoxicity associated with pyrrolizidine alkaloid (Crotalaria spp) ingestion in a horse on Easter Island

Abstract

Since 1984, a significant number of privately owned and feral horses on Easter Island have died of a syndrome consisting of progressive anorexia, weight loss, obtundation, and other central nervous system abnormalities. A single horse experiencing clinical signs of the reported syndrome was identified, examined and necropsied. Clinical signs included inappetence, emaciation, ataxia and icterus. Gross necropsy findings included hepatic enlargement and mottling, ascites and gastric impaction. Histopathological lesions included hepatic hemorrhage and necrosis, periportal megalocytosis, portal fibrosis, bile duct hyperplasia and multinucleate hepatocytes. Crotalaria grahamiana and C pallida, were identified in the pasture of the presenting horse, and found to be widespread on the island. Alkaloid fingerprinting identified grahamine, monocrotalin, and a grahamine analog in C grahamiana. A retrorsine analog and a senecionine analog were identified in C pallida. The highly characteristic lesions and the identification of pyrrolizidine alkaloids in the 2 plants strongly suggest that ingestion of 1 or both of the Crotalaria species led to chronic liver damage and hepatic encephalopathy in the presenting horse. Widespread distribution of C grahamiana on the island and reported temporal and seasonal trends in incidence among horses and cattle suggest that C grahamiana may be responsible for extensive morbidity and mortality among horses and cattle on Easter Island.