Pyrrolizidine alkaloidosis is a disease caused by chronic poisoning from ingesting plants that contain pyrrolizidine alkaloids (PAs), a group of more than 30 phytotoxins produced by various plants as a natural
defense mechanism.
These toxins are metabolized in the liver into highly reactive pyrroles, which cause cytotoxic effects by cross-linking DNA and other cellular macromolecules, leading to irreversible damage in target tissues, primarily the liver.
The condition typically results in hepatic failure and is characterized by a delayed onset of clinical signs, often appearing weeks or months after exposure, even after
consumption of the toxic plants has ceased.
Pyrrolizidine alkaloidosis is most commonly
associated with plants from the genera Senecio, Crotalaria, Heliotropium, Amsinckia, Echium, Cynoglossum, and Trichodesma, which grow in temperate, tropical, or subtropical climates.
Animals such as cattle, horses, pigs, and farmed deer are
particularly susceptible, with young, growing animals being most vulnerable.
The disease can occur through ingestion of fresh plants, hay, silage, or contaminated grain, as some toxic compounds survive drying processes.
Clinically, the disease manifests as
progressive liver damage, with signs including loss of condition, anorexia, dullness, diarrhea, ascites, jaundice, and hepatic encephalopathy such as head-pressing, aimless wandering, or aggressive behavior.