Further investigation of equine fescue oedema induced by Mediterranean tall fescue (Lolium arundinaceum) infected with selected fungal endophytes (Epichloë coenophiala).

This research article investigates equine fescue oedema, a disease in horses caused by ingestion of certain fungal-infected grasses, and whether treatment with a corticosteroid and anti-histamine medication could prevent the disease. However, despite treatment, horses still developed the disease indicating that the certain compounds in the grass, namely lolines or N-acetyl norloline, may not be the cause.

Research Aim and Methodology

• The main goal of the study was to establish if equine fescue oedema (EFO) in horses, triggered by grazing Mediterranean-type tall fescue infected with specific endophytes, could be prevented by treatment with the corticosteroid methylprednisolone and anti-histamine cetirizine.
• The researchers also set out to determine the concentrations of lolines, specifically N-acetyl norloline (NANL), in grasses grazed by horses that did and did not develop EFO.
• The study was conducted using four horses that were grazed on AR542-infected Mediterranean tall fescue pasture. Half of these horses were treated with a mix of methylprednisolone and cetirizine hydrochloride.
• Two more horses grazed on meadow fescue infected with a naturally-occurring endophyte for comparison. All horses were observed for EFO symptoms and blood samples were collected for total protein (TP) analysis.
• Pasture samples were also analyzed for concentrations of lolines using gas chromatography.

Findings of the Study

• The results showed that both treated and untreated horses which grazed on the infected Mediterranean tall fescue developed signs of EFO, whereas horses feeding on meadow fescue did not show any symptoms.
• Furthermore, the serum TP in all horses that fed on Mediterranean tall fescue were detected to be less than 45 g/L. In contrast, horses that fed on meadow fescue maintained higher TP levels, above 60 g/L.
• All horses that consumed Mediterranean tall fescue showed marked oedema and eosinophilic inflammation in the intestines. However, concentrations of total lolines and N-acetyl norloline (NANL) in the Mediterranean tall fescue associated with EFO appeared to be lower than in meadow fescue.

Conclusions and Clinical Relevance

• The findings suggest that treatment with methylprednisolone and cetirizine did not prevent EFO in horses grazing Mediterranean tall fescue infected with the AR542 endophyte.
• From the pasture analysis, it’s also suggested that lolines or NANL are unlikely to be the causative agent of this disease, hence the mechanisms of EFO remain unclear.