Megaesophagus in Friesian horses associated with muscular hypertrophy of the caudal esophagus.

The research study explores the prevalence of esophageal disease, specifically megaesophagus beyond normal size associated with muscular thickening, in Friesian horses. The key finding identifies a higher prevalence of this severe condition in Friesian breed compared to others.

Research Overview

• This study is a retrospective one, meaning that it analyzes past data, specifically regarding the prevalence and pathological traits of esophageal disease in 852 horses, which included 17 Friesians. This was done over a span of six years at the Diagnostic Center for Population and Animal Health.
• The horses that underwent this necropsy procedure had exhibited a range of esophageal anomalies, including muscular hypertrophy (enlargement), hemorrhage, megaesophagus, erosion or ulceration of the esophagus, obstruction, tears, secondary neoplasms, lymphoid patches, thinned walls and esophagitis (inflammation in lining of esophagus).
• It is notable that some of these conditions coincided in a single horse.

Findings on Severe Esophageal Disease

• Among these horses, 10 were reported to have died or were euthanized due to severe esophageal illness. The causes included megaesophagus leading to tears, esophageal obstruction due to a food bolus, and esophagitis.
• Significantly, all six horses diagnosed with megaesophagus were of the Friesian breed, and there was no explicit cause stated for the disease in the corresponding autopsy reports.
• However, it was found that 5 of these Friesian horses showed considerable hypertrophy in the muscular section of the caudal esophagus, with a wall thickness above the normal range.
• Upon microscopic examination of these Friesians’ esophagi, the researchers discovered smooth muscle hypertrophy, but there was no discernible fibrosis, degenerative losses, or loss of myenteric plexi (networks of neurons in the gastrointestinal tract).
• In comparison, the severe esophageal disease in the four non-Friesian horses was found to be due to obstruction by a food bolus in the esophagus or severe esophagitis, but none exhibited muscular hypertrophy.

Conclusions

• The research concluded that Friesian horses have a significantly higher risk of severe esophageal disease compared to horses of other breeds.
• Specifically, megaesophagus combined with noteworthy muscular hypertrophy in the caudal esophagus is more common among Friesians.

These findings can assist in better understanding, diagnosing, and treating such esophageal conditions in Friesian horses.