Crotalaria spectabilis poisoning in horses fed contaminating oats.

The present report describes the clinical and pathological changes induced by the consumption of oats contaminated with Crotalaria spectabilis seeds by horses. Eighty horses were exposed to oats containing 10 g/kg of C. spectabilis seeds with 0.46% pyrrolizidine alkaloids, and 21 horses died within a 6-month period. Clinical signs included jaundice, apathy, a hypotonic tongue, ataxia, hyporexia, weight loss, aimless wandering, violent behavior, and proprioceptive deficits. Pathological findings were predominant in the liver and included periportal bridging fibrosis, megalocytosis, centrilobular necrosis, and bile stasis. Other findings were Alzheimer's type II astrocytes in the cortex, midbrain, basal nuclei, brainstem and pons; multifocal edema and hemorrhage in the lungs; and degeneration and necrosis of the tubular epithelium of kidneys. Horses are highly sensitive to pyrrolizidine alkaloid-containing plants, and the observed clinical and pathological findings are typical of this poisoning. The seeds were planted, and botanical identification of the adult plants confirmed the diagnosis of C. spectabilis poisoning.