Vet’s View: Equine Gastric Ulcer Syndrome

Vet’s View: Equine Gastric Ulcer Syndrome
Vet’s View: Equine Gastric Ulcer Syndrome

Equine Gastric Ulcer Syndrome

In the past few years equine gastric ulcer syndrome has gained greater recognition as an important condition affecting both our performance and recreational equine partners. In this condition, the mucosa of the lower esophagus, stomach and upper duodenum (small intestine) become eroded or ulcerated. There are two types of mucosa in the stomach, a squamous portion and a glandular portion. These regions of the stomach are divided by a junction called the margo plicatus. The most common area for gastric ulcers to develop is on the squamous portion of the stomach, near the margo plicatus. In the affected horse, the acidity of the stomach overrides the protective mechanisms of the mucosa and the epithelium becomes eroded and eventually ulcerated.

The risk factors for development of equine gastric ulcer syndrome continues to be investigated by researchers. One of the largest risk factors for our horses is athletic performance and even recreational use. One study revealed that up to 90% of racehorses were affected by gastric ulcers. Another study found that up to 60% of horses used for sport or pleasure use were affected. Other identified risk factors include high concentrate and low forage diets, and interrupted feeding schedules leading to periods of fasting. In a nutshell, these risk factors increase the exposure of the mucosa to gastric acids and/or reduce the protective mechanisms, such as the acid buffering capacity, of the stomach.

A common misconception is that overzealous administration of non-steroidal anti-inflammatories (NSAIDs, ex. phenylbutazone) is the most common cause of gastric ulcers.  Although NSAIDs can contribute to the development of gastric ulcers, the first and most common adverse effect from NSAID use is actually right dorsal colitis, an inflammatory condition affecting the colon. These adverse effects are because NSAIDs inhibit the endogenous secretion of prostaglandins. Prostaglandins play an important role in protecting the mucosa from gastric acids by promoting mucus and bicarbonate secretions and altering mucosal blood flow. Prostaglandin secretion can also be inhibited by stress, and this is a key contributor to the development of gastric ulcers in performance horses. Stressful events for your horse such as showing, travelling or illness will increase your horse’s susceptibility to develop ulcers and is why we often target treatment at those times.

So how would you know if your horse is affected by equine gastric ulcer syndrome? The clinical signs of this syndrome are notoriously vague and often this condition is diagnosed when other diagnostics yielded no results. Even low grade ulcers can cause your horse pain and discomfort. How this discomfort manifests in horses varies greatly depending on the severity of the lesions and the individual character of the horse. Changes in behaviour or a history of misbehaviour are commonly cited. Sensitivity to palpation of the girth area or “girthiness”, irritability under saddle, and resistance to perform can also be observed. A reduced appetite, teeth grinding, and poor body condition are also common clinical signs. Gastric ulcers can also be a cause of intermittent, low grade colic. Affected horses often present with a history of frequent bouts of colic that respond to medical management on the farm or in the hospital.

Equine gastric ulcer syndrome can be definitively diagnosed through gastroscopy, or endoscopic examination of the stomach. In this procedure, the horse undergoes standing sedation, and an endoscopic camera is passed down the horse’s esophagus into the stomach. The horse is held off of feed and water to ensure that the stomach is as empty as possible. The camera can then be maneuvered around the stomach and esophagus to examine the mucosa and identify any erosions or ulcerations. The severity of the lesions can be graded and their chronicity can be determined. In severe cases, a follow-up gastroscopy may be warranted to evaluate the effectiveness of treatment before it is discontinued.

Ulcer grade 1    Gastric ulcers are most commonly found on the squamous portion of the stomach near the margo plicatus, the junction between the squamous and glandular portions of the stomach. A horse with grade 1 ulcers may have areas of reddening and inflammation, and several areas of eroded or mildly ulcerated mucosa. This image was collected during a gastroscopy.

Ulcer 3   A horse with grade 3 gastric ulcers has extensive areas of deeply ulcerated mucosa. This image shows deep ulcers in the squamous portion of the stomach visualized via gastroscopy.

The mainstay of treatment for equine gastric ulcer syndrome is an oral medication omeprazole, which is only available in Canada as the labelled product “Gastrogard”. This medication is a proton pump inhibitor, which in effect reduces the production of acid by the stomach, thereby making it less acidic. This reduces the incidence of new ulcers developing and promotes healing of those already present. The typical recommendation is a 28 day course of treatment with daily administration of Gastrogard. Ideally the horse is re-evaluated near the end of this period to assess their response to treatment. Once the ulcers have resolved, some horses may be managed well with husbandry changes alone. Other horses, especially those with rigorous training or showing schedules, may require targeted treatment during stressful events to prevent the recurrence of gastric ulcers. Other medications, such as sucralfate, may also be employed in the treatment of gastric ulcers. Sucralfate is an oral medication that is designed to coat damaged mucosa in the esophagus and stomach, and may help speed the healing of ulcers that are present.

By understanding the risk factors for developing gastric ulcers, we can alter the management of our horses in an effort to reduce their incidence. Feeding diets that are primarily forage based with as few concentrates as possible is optimal. In addition, mimicking the horse’s grazing feeding pattern by either offering grass turn out, slow feeder hay nets, or more frequent feedings, can all help reduce your horse’s risk for developing ulcers.  If you feel your horse may be affected by equine gastric ulcer syndrome contact your veterinarian for more information about diagnostic and treatment options.

 

Author: Maia Aspe is originally from Langley, BC and works at Paton & Martin Veterinary Services in Aldergrove, BC. She graduated from the Western College of Veterinary Medicine and prior to that, she majored in Applied Animal
Biology at the University of British Columbia. Maia discovered her passion for equine medicine while competing on the hunter jumper circuit. She appreciates all aspects of the equine veterinary field, but is particularly interested in sports medicine. In her free time, she enjoys riding her horse and spending time in the great outdoors.