Ragwort Toxicity

Hepatotoxicity

• plant toxin ingested over a long period of time
• livestock
  • cattle and horses are more susceptible than sheep
  • livestock will not normally eat the fresh plant
  • most cases arise in horses and cattle consuming ragwort in hay or silage
• pyrrolizidine alkaloids
  • toxic principle converted in the body to the toxic intermediate pyrroles and their esters
  • cause intitial and continued damage to hepatocytes
  • have an anti-mitotic effect whilst allowing continued synthesis within the cell and its nucleus
    • causes a marked increase in the size of parenchymal cells, a phenomenon termed 'megalocytosis'
    • these very enlarged hepatocytes can be up to 20 times bigger
    • the enlarged cells are closely apposed so that the sinusoids may not be evident
• it is likely that the vascular component of the attempted repair of the chronic damage by fibrosis (really a type of granulation tissue) aids the shunting from the portal triads to the central vein and thereby bypassing the hepatocytes
• other plant and fungal toxins perform in the same way

Gross

• slightly enlarged liver
• pale in colour
• very firm to section

Microscopically

• necrosis
• haemorrhage
• diffuse fibrosis

Also known as:

Senecio jacobea