Senecio poisoning in horses primarily affects which organ system?

• A. Liver
• B. Kidneys
• C. Heart
• D. Lungs

Answer: (A)

Senecio plants contain pyrrolizidine alkaloids that are bioactivated in the liver, causing hepatocellular and biliary injury. In horses, this hepatic damage is the primary effect, leading to chronic liver disease, impaired liver function, and secondary photosensitization from accumulated phylloerythrin. Because the liver is the main organ affected by these toxins, the organ system involved is the hepatic system. The kidneys, heart, and lungs are not the primary targets of Senecio pyrrolizidine alkaloids.