Confusion often surrounds the cause, diagnosis and treatment of gastric ulcers. Richard Hepburn MRCVS draws on the latest veterinary thinking to answer horse owners' most frequent questions
Q What’s the difference between squamous and glandular ulcers?
Squamous gastric ulcers affect the top, white-coloured third of the stomach, and reflect increased acid exposure of the tissue.
These ulcers form quickly and are consistently associated with changes in appetite, slowed eating and poor performance. Inconsistent changes in behaviour and/or attitude can also occur.
Squamous ulcers can occur with daytime forage deprivation, lack of access to water, high-starch diets, pelleted feeds, straw feeding, intense exercise, travel, a change in housing and lack of daily horse-to-horse contact.
Treatment with an equine formulation of the acid suppressant drug omeprazole is consistently very effective, with most lesions healing within 14-28 days.
Glandular ulcers affect the pink, bottom two-thirds of the stomach, in particular the final part.
Ulcers here form slowly and reflect failure of the mucus coat that protects glandular tissue from acid. It is likely that several different causes — physical, toxic, bacterial or physiological — contribute to this failure. The clinical signs are more variable, and may or may not include appetite change and/or weight loss. Some horses may start to resent the girth being tightened, but this is not specific.
Treatment with omeprazole alone is much less effective than in cases of squamous disease (25% healed after 28-35 days). Instead, a combination of omeprazole and the mucosal protectant sucralfate is used, leading to a 68% healing rate.
Q Why do so many more horses now seem to suffer from ulcers?
The prevalence of squamous gastric ulceration in racehorses in full training is unchanged from 30 years ago, at more than 80%. Interestingly though there are some yards where ulcers are much less frequent, most likely due to protective feeding and management strategies. In sport and leisure horses the prevalence is lower, at 17-60%.
The occurrence of glandular ulceration in racehorses and sport and leisure horses is 30-60%.
Any apparent increase is more likely to be due to increased awareness of the condition, and hence increased willingness to have gastroscopy performed. For example, in 2005 I gastroscoped 150 horses — this year I have looked at more than 400.
Q A horse at my yard has hindgut ulcers — is this something different?
There is much debate as to what “hindgut ulcers” actually are. The study originally performed to identify hindgut ulcers used horses from abattoirs without any clinical history, and so the relevance of the lesions detected is unclear.
A hindgut disease we have more understanding of is inflammatory bowel disease (IBD). In this condition large portions of the hindgut become inflamed and thickened, even shedding part of their surface layers. This causes weight loss, intermittent diarrhoea and/or recurrent colic, but rarely affects behaviour or performance.
Diagnosis of IBD is made by a combination of abdominal ultrasound, blood tests to identify low protein levels, absorption studies and intestinal biopsy. Treatment involves three months of the anti-inflammatory corticosteroid prednisolone, and is successful in 70% of cases.
Further study into whether hindgut ulcers are able to cause behavioural change and poor performance is required, as these signs are rarely seen in IBD, which is a more severe hindgut disease.
Q Are any of the new screening methods effective?
Bleeding from gastric ulcers is not a common or consistent finding, so faecal blood/albumin testing is not recommended. The test is also unable to distinguish between squamous and glandular disease, and so targeted treatment is not possible.
A better screening approach is to look for significant clinical signs developing in your horse: appetite change, slowed eating, below-par performance and potentially development of behavioural change or resentment of girthing.
The Succeed test is a combined faecal occult blood and albumin test that detects blood (originating from anywhere within the gastrointestinal tract) and albumin (lost when the large intestine is inflamed).
It is marketed as a screening test for gastric ulcers (described as “foregut” bleeding), yet a recent Australian study of 44 horses with squamous and glandular ulceration showed no association between the test result and gastroscopy findings.
The test is also marketed as identifying infectious, inflammatory, traumatic, neoplastic and parasitic causes of large intestinal protein leakage, broadly classified as hindgut ulcers. False positive results can occur, however, in horses that have recently had endoscopy or dentistry, during ovulation in mares, in horses with exercise-induced lung bleeding, for five days after deworming, 24 hours after a rectal examination and in horses that have eaten hard or rough particles of feed.
Q Could my horse’s recent spookiness be due to ulcers?
In racehorses, squamous ulceration can reduce stride length, limit training progression and reduce the time to fatigue — potentially as a result of low-grade pain affecting abdominal strength and mechanics of breathing. Similarly, treatment studies have shown improved performance measures in racehorses after ulcer resolution.
The evidence for more specific signs such as spooking or refusing, or for behavioural change, is anecdotal. If ulcers in an individual horse are suspected to be causing these then clinical improvement should occur as the ulcers heal, and so a critical appraisal of the value of treatment at repeat gastroscopy is essential.
Q My horse is a healthy-looking good-doer. Could he still have ulcers?
Yes, there is a population of horses that appear normal, but who benefit from diagnosis and treatment of ulceration. At the same time there are horses that have the same ulcers yet show no clinical signs and no benefit from treatment.
Unfortunately it is not possible to distinguish these cases by endoscopy alone, and so a period of test treatment with omeprazole is used to assess their ulcer relevance.
Q Are ulcers more likely in any particular breed?
Thoroughbreds appear to have a breed predisposition to squamous ulcers, whereas warmbloods are more frequently found to have glandular lesions.
Most horses will be average acid secretors — while a few will produce either more or less. It is reasonable to expect high acid secretors to be more likely to have gastric ulcers.
Q My vet has prescribed a form of omeprazole. Is it safe to use?
Gastrogard is the original equine-specific form of omeprazole.
Safety studies performed on Gastrogard (overdose and prolonged duration studies) did not show any evidence of significant side effects. Hundreds of thousands of doses have been given worldwide over the last 20 years, with minimal adverse events reported (far fewer than for common drugs such as bute or antibiotics).
In the UK there are now two generic forms available: UlcerGold and Peptizole. Studies and clinical experience suggest there is little difference between the available formulations in most horses.
• NEXT WEEK: part II — how to manage ulcers, plus a new melanoma vaccine
Ref: Horse & Hound; 17 December 2015