Hepatoencephalopathy syndrome due to Cassia occidentalis (Leguminosae, Caesalpinioideae) seed ingestion in horses.

This research describes an outbreak of Cassia occidentalis poisoning in horses resulting from ingestion of contaminated feed. This toxic plant causes hepatoencephalopathy syndrome, associated with liver damage and neurological symptoms, often leading to sudden deaths in affected horses.

Introduction of Cassia occidentalis and its Effects

• Cassia occidentalis is a bush from the Leguminosae family, subfamily Caesalpinioideae, recognized as a toxic plant of veterinary interest due to its occasional contamination of animal rations.
• This plant’s poisoning triggers hepatoencephalopathy syndrome, a condition linked to liver damage and updates in the nervous system, frequently leading to sudden equine fatalities.

Case Description from the Study

• In this study, twenty mares ingested ground corn contaminated with 8% of C. occidentalis seeds, leading to the poisoning.
• Among these, 12 died: eight were found dead, two died 6 hours after showing signs of hepatoencephalopathy, and the remaining two were euthanized after showing severe clinical signs.
• The surviving eight mares showed mild depression and decreased appetite but improved with treatment and did not present any lasting clinical effects.

Postmortem Findings and Histopathological Observations

• Six horses that underwent a necropsy indicated an enhanced hepatic lobular pattern and consistently observed a large number of seeds within the large intestine.
• The main histological findings included hepatocellular pericentrolobular necrosis, responsible for liver damage, and cerebral oedema that affects the brain.
• In a mare, mild multifocal semimembranosus rhabdomyocytic necrosis and haemorrhage were observed, indicative of muscle damage and internal bleeding.

Seed Examination and Resultant Plants

• Seeds collected from the intestinal contents and sifted from the contaminated feed were planted to confirm the toxic plant’s identity.
• The observation of the resultant plants’ leaves, flowers, fruits and seeds confirmed that they were indeed Cassia occidentalis.

Conclusion and Recommendations

• Horses poisoned by C. occidentalis shows signs associated with hepatoencephalopathy and usually die suddenly, with primary lesions involving the liver and secondary involvement of the central nervous system.
• Thus, when dealing with horses that show such symptoms, C. occidentalis poisoning should be considered a differential diagnosis.
• Sufficient caution should be employed when preparing horse feed to ensure its contamination with this toxic plant’s seeds is avoided.