Toxic peripheral neuropathy of chicks fed Senna occidentalis seeds

Plants of the genus Senna (formerly Cassia) are poisonous to livestock and other laboratory animals, leading to a syndrome of a widespread muscle degeneration, incoordination, recumbence, and death. The main histologic lesion is necrosis of skeletal muscle fibers. Recently, a mitochondrial myopathy with ragged-red and cytochrome oxidase (COX)-negative muscle fibers was recognized in hens chronically intoxicated with parts of seeds of S. occidentalis. The purpose of the present work was to investigate if there was peripheral nerve involvement in the acute intoxication of chicks with S. occidentalis seeds. Teasing of individual fibers revealed signs of extensive axonal damage with myelin ovoids. Ultrathin sections confirmed the axonal damage. Axons were filled with membranes, some residual disorganized filaments, and enlarged mitochondria. In some instances the axon disappeared and there was secondary degeneration of the myelin sheath. The present work is the first description of the neurotoxic effect of S. occidentalis intoxication. Future work should attempt to determine the mechanisms involved in this neuropathy.