Pyrrole detection and the pathologic progression of Cynoglossum officinale (houndstongue) poisoning in horses.

The research in this article investigates the effects of the houndstongue plant, specifically its pyrrolizidine alkaloids (PAs), on horses and develops methods for diagnosing PA poisoning. The results show that ingestion of this plant, common in western America and Europe, can cause severe liver disease in horses and that identifying pyrrole metabolites can be a useful tool for diagnosing PA poisoning.

Objective and Methodology

• The main goal of this study was to develop diagnostic techniques for PA poisoning in horses and to explore the pathologic progression of the condition induced by houndstongue intoxication.
• In the experiment, six horses were administered a houndstongue suspension containing either 5 or 15 mg/kg total PA, daily for two weeks. Two horses were given ground alfalfa for the same duration as a control group.
• Throughout the study, liver biopsy samples were taken and serum biochemical and hematologic values were evaluated biweekly.

Results and Findings

• Within a week of dosing, the horses administered with the higher concentration of PA (15 mg/kg) developed severe liver disease with symptoms including altered bile acid metabolism, elevated serum enzymes, and widespread hepatocellular necrosis. The animals’ health worsened and they had to be euthanized.
• The horses exposed to a lower concentration of PA (5 mg/kg) showed symptoms of depression, temporary spike in serum enzymes and bile acids, and minor hepatocellular necrosis with fibrosis. The biochemical changes ceased by the sixth and eighth weeks, however, the histologic changes persisted with significantly enlarged cells by the fourteenth week.
• Throughout the experiment, the rate of liver cell proliferation remained consistent. Meanwhile, the mitotic rate or cell division in biliary cells had a noticeable increase pleasingly fitting with the histologic changes.
• Post-mortem examination of the horses revealed the presence of hepatic tissue-bound pyrroles (PA metabolites) in their samples. These pyrroles were detected and assessed using gas chromatography/mass spectrometry and a photometric procedure with Ehrlich’s reagent.

Conclusions

• This research concludes that pyrrole extraction and identification is useful in documenting PA exposure in cases of houndstongue intoxication.
• The study also illuminates the severe toxic effects of houndstongue on horses, particularly the damage it can cause to the liver.