Dr. Tania Sundra

26 January 2021

Equine Gastric Disease

The umbrella term Equine Gastric Ulcer Syndrome (EGUS) has previously been used to describe both Equine Squamous Gastric Disease (ESGD) & Equine Glandular Gastric Disease (EGGD). However, we now know that they are distinct diseases and are completely unrelated in terms of their appearance, risk factors, treatment and management. They both just happen to occur in the horse’s stomach!

The only way to tell IF your horse has gastric disease and what TYPE of disease it has, is to gastroscope your horse.

It is important for owners to understand that there is no ‘standard protocol’ for the treatment of either ESGD or EGGD. Every lesion is different. Every horse is different. As with anything regarding with your horse’s health, be wary of those offering a one-size-fits-all approach. The information below represents a summary of recent published research as well as our clinical experience.


PART 1 : SQUAMOUS DISEASE

The top (proximal) half of the stomach is covered by what’s called ‘squamous mucosa’. It’s similar to the lining of your mouth. If we add acid to this squamous lining, ulcers develop. Squamous disease is essentially is acid getting onto to a tissue that’s not designed to be covered by acid, has limited defence mechanisms against acid and where the acid has a corrosive and burning effect.

RISK FACTORS FOR THE DEVELOPMENT OF SQUAMOUS DISEASE

Squamous disease is what we call a multifactorial problem. It is largely due to diet and exercise. What we feed, when we feed it, and how we exercise our horses plays a large role in the development of this disease.

  • Duration of exercise – Horses involved in strenuous exercise such as thoroughbreds, standardbreds and endurance horses are more likely to develop squamous ulcers. The pH of the proximal stomach reduces to less than 4 when horses begin trotting. However, the level of acid exposure does not differ between trot and faster gaits.  It is really the duration of exercise and not the intensity that increases the risk of a horse developing squamous ulcers.
  • Soluble carbohydrates – if you feed more than one gram of soluble carbohydrates per kilogram of body weight per meal, it doubles the likelihood causing squamous ulcers in your horse.
  • Water deprivation leads to a 3x increased risk of a horse developing squamous disease.
  • Timing of feeding – recent behavioural studies have shown that horses reduce their feed intake overnight (ie. when they are sleeping). During this time, the pH of the stomach drops to below 4 which means that the risk for developing squamous disease in horses who are exercised first thing in the morning on an empty stomach are high.

TREATMENT OF SQUAMOUS DISEASE

As we know that squamous disease is a result of acid injury to the squamous mucosa, treatment involves suppressing that acid to allow the ulcers to heal.

To do this we use a drug called omeprazole which works by turning off the acid pumps in the stomach. Studies have shown up to 70-80 % healing rate of squamous ulcers using oral omeprazole. With good management and appropriate dosing, treatment duration typically ranges from 14-28 days depending on the grade of ESGD present.

It is important to note that the absorption of omeprazole is reduced by the presence of food. Owners may think that omeprazole just needs to get into the stomach to neutralise the acid. This isn’t the case! Omeprazole needs to leave the stomach, enter the small intestine, get absorbed into the bloodstream and then return to the stomach to ‘switch off’  the acid pumps. The presence of food in the stomach has been shown to dramatically reduce the bioavailability of oral omeprazole. We therefore recommend that owners administer omeprazole first thing in the morning, approximately 30-60mins prior to giving your horse their breakfast. If oral omeprazole is administered appropriately, and management factors are addressed, most lesions should heal within 2-4 weeks. If they fail to heal, then other treatment and management options should be considered rather than continuing to treat for longer.

MANAGEMENT OF SQUAMOUS DISEASE

Management changes are important to ensure treatment success and to reduce the risk of the recurrence of squamous disease. We recommend the following :

  • DIET : feed a low carbohydrate feed such as Hygain Zero/Balanced or Prydes Easisport. If extra calories are required consider adding ‘fats’ in the form of oils (eg. rice bran oil, canola oil). Ensure you feed a good quality, palatable source of roughage such as lucerne hay.
  • PRE-EXERCISE FEEDING : feeding 1-2 biscuits of lucerne hay or 3-5L of lucerne chaff prior to exercise will help prevent “splashing” of acid onto the squamous mucosa when the horse is exercised.
  • TIMING OF EXERCISE : As mentioned above, the pH of the horse’s stomach is lowest first thing in the morning and highest in the late afternoon. We therefore recommend exercising horses who are prone to developing squamous disease in the afternoon/evening when the risk is lowest.
  • DURATION OF EXERCISE : It has been shown that the longer you exercise your horse, the higher the risk of developing squamous disease. We therefore recommend high intensity, short duration exercise with minimal warm-up and cool down periods for horses prone to squamous disease. However, each horse is different and underlying and/or previous lameness issues should be taken into consideration when developing an exercise program for your horse.
  • WATER : This should go without saying but horses must have free-access to clean, fresh drinking water at all times.

PART 2 : GLANDULAR DISEASE (EGGD)

Equine gastric glandular disease (EGGD) is a less well-understood condition. It relates to disease that occurs in the lower half of the stomach which is lined by what’s called, glandular mucosa. The glandular mucosa, unlike the squamous mucosa is used to living in an acid environment (this is the part of the stomach where the acid is produced) and usually has good defence mechanisms against it. However, for reasons we don’t fully understand, these defence mechanisms breakdown leading to disease in this part of the stomach. What we know about squamous disease cannot be extrapolated to glandular disease –  they’re entirely different diseases, and we need to treat them as such.

RISK FACTORS FOR THE DEVELOPMENT OF GLANDULAR DISEASE

Risk factors relating to EGGD are not yet fully understood.

  • BREED : Warmblood horse breeds have shown a higher prevalence of this disease
  • TRAINERS : In Thoroughbred horses the trainer has been identified as a potential risk factor.
  • FREQUENCY OF EXERCISE : One study showed that showjumpers exercised 6-7 times per week were 3.5x more likely to develop glandular disease compared with horses exercised less 5 days per week.
  • STRESS : There is an increasing body of evidence to suggest that behavioural stress plays a large role in the development of glandular disease and more work is needed in this area.

TREATMENT OF GLANDULAR DISEASE

Unlike squamous disease, oral omeprazole is not effective in treating glandular disease. This is not just our opinion, many experts around the world DO NOT recommend oral omeprazole in the treatment of this disease. There is currently no medication registered for the treatment of glandular disease in horses. Some drug companies advocate the use of omeprazole + sucralfate but published evidence shows the rate of healing with this combination to only be approximately 20% after 4 weeks. Ideally both drugs would be administered on an empty stomach, would not be administered within an hour of each other and omeprazole would be administered around one hour prior to feeding and in advance of exercise. This will obviously be impractical for many owners.

Even though acid may not be the reason disease develops in the glandular mucosa, it likely plays a role in preventing these lesions from healing. In our experience, and based on recent scientific evidence we will recommend one of the following treatment options for glandular disease.

  •  Long-acting Injectable Omeprazole. This medication is administered to horses via intramuscular injection every 5-7 days. 75% healing rates and 100% improvement rates have been reported in 1 study. This is a compounded medication that is not currently registered for use in horses. Reported side effects include a transient, non-painful swelling that develops at the injection site. To minimise this risk we recommend injection into the gluteals (rump) and to ensure the injection is not given immediately before or after exercise. Splitting the dose into smaller volumes and injecting it into multiple sites is also not recommended as this will likely reduce the efficacy of the medication.
  • Esomeprazole. A more ‘potent’ version of omeprazole, esomeprazole is used extensively in humans with peptic ulcer disease. One study demonstrated that esomeprazole was associated with the healing of both squamous and glandular lesions in 4/5 horses which failed to respond to oral omeprazole monotherapy.
  • Misoprostol. Misoprostol is a registered human medication, which is not currently licensed for use in horses. The drug is in tablet form and administered orally, twice a day for the treatment of glandular disease. One study has shown a 98% improvement and 72% healing of glandular lesions in horses using misoprostol. Owners should be made aware of human health concerns whilst handling this medication.

In cases that do not respond to any of the options above, we will sometimes recommend combination therapies or use corticosteroids if we suspect an underlying inflammatory component. Some lesions may also warrant biopsy or removal via electrocautery, but we will discuss these options with you on a case-by-case basis. There is little to no evidence for the use of antibiotics in the treatment of glandular disease. In the interest of good antimicrobial stewardship, it should only be considered in cases that fail to respond to treatment and where histopathological findings support their use.

MANAGEMENT OF GLANDULAR DISEASE

Glandular disease is NOT believed to be a disease of diet and recommendations for managing squamous disease will have no effect on the prevention of glandular lesions. However, as previously stated, behavioural stress as well as frequency of exercise plays a large role in the development of this condition. Our recommendations for managing glandular disease include:

  • FREQUENCY OF EXERCISE : Provide a minimum of 2-3 complete rest days per week.
  • REDUCING STRESS :
    • Turnout should be provided where possible provided the horse does not become stressed by this management. Some horses may be less stressed in a stable environment
    • Minimise environmental changes wherever possible. Develop a routine and stick to it.
    • Provide a companion and minimise changes to equine companions where possible.
    • Minimise the number of riders

The only way to tell IF your horse has gastric disease and what TYPE of disease it has, is to gastroscope your horse. We offer a mobile gastroscopy service, allowing us to scope your horse on your property.
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