Equine Gastric Ulcer Syndrome (EGUS)

Normal stomach

EGUS is a term used to describe erosive and ulcerative diseases of the stomach of the horse. It is more specifically divided into 2 terms that describe the region of the stomach that is affected. Equine Squamous Gastric Disease (ESGD) and Equine Glandular Gastric Disease (EGGD).

In performance horses there is an 11-93% prevalence of ESGD which is dependent upon risk factors such as the intensity of training, the number of days per week in training, home environment, diet and feeding management, presence or absence of direct contact with other horses, the type of music in the barn, and access to water. The prevalence and risk factors for EGGD is less well understood.

Clinical signs may include poor appetite or “picky eating”, poor body condition or weight loss, chronic diarrhea, poor/dull hair coat, teeth grinding, behavioral changes including aggressiveness or nervousness, acute or recurrent colic, pain or discomfort while eating, poor performance, and decreased ability to improve with training.

EGGD in the pylorus – hemorrhagic ulcer

The only way to definitively diagnose gastric ulcers in the horse is to perform a gastroscopy. It is important that this procedure is performed after adequate fasting to empty the stomach and to allow visualization of the entire stomach. There is no known relationship between squamous ulcers and glandular ulcers so both areas of the stomach need to be evaluated. It is also important to note that if a trial treatment is performed in a horse that is suspected of having gastric ulcers, gastroscopy is recommended if the horse fails to respond to treatment because some horses do not resolve clinical signs until complete healing of the ulcers has occurred.

A grading system exists to describe the severity of ESGD. It ranges from a score of 0 (Normal squamous mucosa) to 4 (Extensive lesions with areas of deep ulceration). This system was developed to allow for a consistent understanding of the severity of disease between veterinarians evaluating horses. No such organized system exists for EGGD so glandular ulcers are described as present or absent and based on their anatomic location, distribution, and the appearance of the lesions.

Squamous ulcers – Grade 2

How do horses develop EGUS? Horses get squamous ulcers (ESGD) due to increased exposure of the squamous mucosa to acid. Diet and exercise play a direct role in this increased exposure. It occurs during exercise when acidic stomach contents are pushed up into the squamous area of the stomach by increased pressure in the abdomen when horses are exercising at any gait faster than a walk. There is increased risk of developing ulcers with an increase in the intensity and duration of training due to the increased amount of time that the squamous mucosa is exposed to high levels of acid. In addition, horses on high concentrate diets have an increased amount of acid in the stomach due to the breakdown of sugars in those feeds into additional acids by bacterial fermentation.

The development of glandular ulcers (EGGD) is poorly understood since this area of the stomach is normally exposed to highly acidic gastric contents but it is thought to be due to the breakdown of the normal defense mechanisms that protect it from those acidic gastric contents. In the horse the factors that cause the loss of the protective mechanisms have not been determined. Experimental studies have not proven a causative relationship between NSAID use and gastric ulcers.

Treatment and Prevention The suppression of gastric acid secretion is indicated in the management of both ESGD and EGGD. Omeprazole is a proton-pump inhibitor that irreversibly impairs the pump that secretes acid forcing new pumps to be created before acid production can be resumed. GastroGard is an omeprazole product that is specifically formulated to be protected from breakdown by stomach acid. It is proven to be effective at healing squamous ulcers (ESGD) at a dose of 4 mg/kg given orally daily for 28 days with 70-77% healing rates reported. Re-evaluation with gastroscopy is recommended before treatment is discontinued to be sure that the ulcers are completed healed.

Squamous ulcers – Grade 3

Glandular ulcers (EGGD) can be more difficult to heal with reports of only 25% of glandular ulcers healed in 28-35 days of omeprazole therapy. Possible explanations include the necessity for longer duration of therapy, inadequate acid suppression, possible secondary bacterial infection or that acid suppression treatment alone may be inadequate. Therefore, the use of mucosal protectants such as sucralfate and misoprostol are often included in the treatment of EGGD. A minimum of 8 weeks of combination therapy is recommended. Healing rates of 67.5% were reported with the combined use of omeprazole and sucralfate. Repeat gastroscopy should be performed before discontinuation of therapy in the treatment of EGGD as well. If lesions fail to heal, mucosal biopsy is recommended.

Preventative therapy can include medications, diet and feeding recommendations, and training and environmental management suggestions. It is best approached on an individual case basis.

If you think your horse may have gastric ulcers, please contact the veterinarians at Atlantic Equine Services to schedule a gastroscopy. We will formulate a specific treatment plan for your horse based on the results of evaluation and work with you to develop a management program for prevention once the ulcers are healed. Please contact us if you have questions or would like more information about EGUS.

Anatomy of the horse’s stomach

Gastroscopy being performed on a sedated horse.

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