Ragwart (Senecio jacobea) is notorious as a poisonous plant that affects horses. The toxic chemicals are pyrrolizidine alkaloids. Among common plants containing pyrrolizidine alkaloids are comfrey (Symphytum officinale) and hound's tongue (Cynoglossum officinale). Pyrrolizidine alkaloid metabolites, reactive pyrroles, bind to DNA and affect
cell division, resulting in abnormal enlargement of cells (megalocytosis, and cell necrosis, abnormalities in the bile duct and liver. Signs reported include colic, jaundice, constipation or diarrhea, wasting, and deranged behavior resulting from degenerative disease of the liver (hepatic encephalopathy). The common terms "hepatic cripples," "sleepy staggers," and
"walkabout disease" summarize the conditions most frequently seen. Owing to the lag time to onset of clinical signs, the disease is often in its advanced stage by the time the animal is examined by a veterinarian.