While megaesophagus is rare in horses, it appears to be more common in Friesian horses compared to other breeds. Utrecht University Equine Hospital reported that Friesians present with megaesophagus at a rate of 2.2% in contrast to 0.5% in other breeds.
Megaesophagus typically occurs from a chronic dilation of the esophagus, esophageal strictures (narrowing) and/or a decrease in peristalsis. Peristalsis is the involuntary constriction and relaxation of the esophageal muscles, which create wave-like movements that push food in the esophagus toward the stomach. Many reported cases of megaesophagus in Friesian horses involve mature or senior horses that present with “choke” induced by an esophageal obstruction related to forage or feed. However, megaesophagus can be congenital (present at birth) and does occur in foals and young horses.
Nursing foals may show early signs of megaesophagus in the form of esophageal dysphagia (difficulty swallowing), with milk draining from one or both nostrils after nursing. Difficulty swallowing is sometimes observed in neonatal foals (less than one-month-old) but often resolves spontaneously as the foal’s swallowing reflexes improve. Difficulty swallowing may also be related to other conditions, such as a cleft palate or neurological issues. If you suspect your foal may be having difficulty swallowing milk after nursing, especially if they are older than one month, consult with your Veterinarian to rule out megaesophagus.
Young horses affected with megaesophagus often present with symptoms of choke after they are weaned and begin ingesting solid food or after they begin creep feeding. These horses will usually present with classic choke symptoms including but not limited to discharge of saliva and feed material from the nostrils and/or mouth, depression, and apparent difficulty in swallowing. Signs of choke can be very subtle and unique to the individual horse with megaesophagus. Owners and caregivers should keep a close watch on their horses to determine behaviors or patterns that may signal the onset of a choke episode.
Aspiration pneumonia is a very serious and common complication that can occur in any horse with megaesophagus, but foals and young horses are especially at risk for pneumonia due to their immature immune systems. When choke occurs, foreign objects, such as bacteria and food particles, may be inhaled into the lungs. While the lungs are not sterile or free from bacteria, they do have their own distinct microbiome, which is unique to the individual horse and can be very sensitive. When aspiration occurs, the sheer number of bacteria in the lungs may overwhelm the natural defense mechanisms of the lungs, and in short order, the horse has pneumonia.
Horses may show no obvious signs during the early stages of pneumonia but may rapidly develop more advanced symptoms such as an increased respiratory rate, difficulty breathing, lethargy, or lack of interest in nursing/eating. Advanced cases of pneumonia typically present with a fever, labored breathing, and nasal discharge.
Aspiration pneumonia requires treatment with antibiotics, and advanced cases may require hospitalization and intensive, round-the-clock care to resolve. Breeders and owners should be aware megaesophagus can occur in foals and young horses. It is important to closely observe any foal which appears to have difficulty swallowing and consult with your veterinarian to rule out any other issues which may cause dysphagia. Chronic choke in young horses may be a key indicator of megaesophagus and require further examination. Additionally, if your foal or young horse is diagnosed with pneumonia related to aspiration, further investigation may be prudent to rule out megaesophagus.
If you have a Friesian that has been diagnosed with megaesophagus, please contact the Fenway Foundation for Friesian Horses to learn how your horse can participate in our current megaesophagus genetic research project. Additionally, please visit our Facebook support group, Equine Megaesophagus, for more information about megaesophagus and tips for how to manage this disease.
Ploeg M, Gröne A, Saey V, de Bruijn CM, Back W, van Weeren PR, et al. Esophageal dysfunction in Friesian horses: morphological features. Vet Pathol. 2014.
Holcombe S.J., Hurcombe, B.S., Barr, H.C., Schott II. 2012. Dysphagia associated with presumed pharyngeal dysfunction in 16 neonatal foals. Equine Veterinary Journal
Foal Pneumonia, Christina S. Cable, DVM, Dipl. ACVS. 1998. The Horse.