Could salivary biomarkers help detect Equine Gastric Ulcer Syndrome (EGUS)

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 Equine Gastric Ulcer Syndrome (EGUS) is a common problem in horses, affecting many disciplines and management systems. Currently, the only reliable way to diagnose EGUS is by gastroscopy – passing a flexible camera into the stomach to look for ulcers.

EGUS is divided into:

• Equine Squamous Gastric Disease (ESGD): ulcers in the upper, squamous portion of the stomach.
• Equine Glandular Gastric Disease (EGGD): ulcers in the lower, glandular portion.

The two forms have different likely causes and may require different management approaches.

While gastroscopy is the gold standard, it has some downsides: it requires specialist equipment, sedation, and a 12–16 hour fast. This can be costly and stressful for both horse and owner.

 

Dr. Marta Matas-Quintanilla and her team investigated whether five biomarkers in saliva could help identify EGUS:

• IL1-F5 - an immune-related protein.
• PIP (prolactin-inducible protein) - linked to immune and inflammatory processes.
• CA VI (carbonic anhydrase VI) - involved in saliva pH regulation.
• Serotransferrin - a protein that transports iron in the blood.
• Albumin - a major blood protein that can appear in saliva during inflammation or injury. 

Saliva is easy to collect, requires no needles, causes minimal stress, and can be taken by someone with basic handling skills; all big advantages for screening horses in the field.

 

The researchers measured these markers in three groups of adult horses, using validated sandwich ELISA tests (high precision and accuracy):

• No EGUS:  22 horses (3 - 20 years old) with no signs of EGUS and a clean gastroscopy.
• EGUS Non-Clinical: 28 horses (3 -14 years old) with no obvious signs, but ulcers seen on gastroscopy. Of these, 6 had ESGD, 11 had EGGD, and 11 had both types.
• EGUS Clinical: 37 horses (3 -18 years old) with obvious EGUS signs (e.g., poor performance, girthiness, changes in appetite or behaviour) and ulcers confirmed by gastroscopy. Of these, 9 had ESGD, 8 had EGGD, and 11 had both. Nine suspected horses with no ulcers on gastroscopy were excluded. 

The research team found that:

• IL1-F5, CA VI, serotransferrin, and albumin were significantly higher in EGUS clinical horses compared to No EGUS horses.
• PIP levels didn’t differ much between No EGUS and EGUS clinical horses.
• EGUS non-clinical horses showed differences in PIP and albumin compared to No EGUS horses.

They report that these markers could moderately distinguish between healthy and ulcer-affected horses, with sensitivity >77% and specificity >65%. The results suggest that measuring certain biomarkers in saliva could one day become a practical screening tool for EGUS. This would be especially useful for:

• Selecting which horses to send for gastroscopy.
• Monitoring horses at risk over time.
• Reducing unnecessary invasive procedures.

 

While gastroscopy will remain the definitive diagnostic method for now, salivary biomarkers offer a promising step toward faster, cheaper, and non-invasive detection of this common condition.

 

For more details, see: 

 

Matas-Quintanilla, Marta, Lynsey Whitacre, Ignacio R. Ipharraguerre, Cándido Gutiérrez-Panizo, and Ana M. Gutiérrez. 2025.

Assessment of Salivary Biomarkers of Gastric Ulcer in Horses from a Clinical Perspective

Animals 15, no. 15: 2251. 

https://doi.org/10.3390/ani15152251

Investigating changes in salivary oxytocin in horse with EGUS

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 Gastric ulcers are common in horses, with studies indicating their presence in approximately 60% of sport horses and up to 90% of Thoroughbred racehorses in training.

Gastric ulcers have been associated with various non-specific clinical signs, including weight loss, reduced appetite, poor physical condition, dullness, colic, diarrhea, poor performance, and behavioural changes. However, many adult horses with gastric ulcers exhibit no obvious signs.

Equine gastric ulcer syndrome (EGUS) is categorised into two types: equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD). A definitive diagnosis requires gastroscopy, a relatively straightforward yet costly procedure.

There is growing interest in identifying biomarkers to assess gastric health non-invasively. One such biomarker is oxytocin, a peptide hormone that plays a role in stress regulation and gastric protection. Salivary oxytocin has been explored as a potential welfare indicator due to its antiulcer and gastric antisecretory properties. It helps reduce acid production and promotes mucosal protection by enhancing blood flow to the stomach lining. Additionally, as oxytocin is involved in social bonding and stress regulation, it may help prevent stress-induced ulcers.

Researchers aimed to investigate differences in salivary oxytocin levels in horses with and without gastric ulcers while also validating an AlphaLISA-based immunoassay for measuring oxytocin in horse saliva. A report of the work is published by BMC Veterinary Research. 

The study involved 102 horses, which were divided into five groups:

·       25 horses with both ESGD and EGGD

·       23 horses with only EGGD

·       21 horses with only ESGD

·       19 horses with other diseases

·       14 healthy horses

Diseased horses were admitted to the Large Animal Teaching Hospital at the University of Copenhagen, Denmark, while healthy horses were sampled at the Veterinary Teaching Hospital of the University of Extremadura, Spain. All examinations took place between February 2022 and March 2023.

The research team found that the assay demonstrated high precision and accuracy for measuring oxytocin in equine saliva. They highlighted the advantages of the AlphaLISA method over conventional ELISA kits, including the elimination of washing steps and the need for a lower sample volume (10 µL vs. 100 µL for ELISA). They point out that this is makes it a more practical option in clinical settings.

Their results showed that healthy horses had higher salivary oxytocin levels compared to those with EGGD or both EGUS types. Horses with only ESGD also had higher oxytocin levels than those with EGGD or both forms of EGUS. Additionally, horses with other diseases had higher oxytocin levels than those with EGGD or mixed EGUS cases.

The findings suggest a potential link between lower oxytocin levels and EGGD or mixed EGUS cases. However, further research is necessary to fully understand oxytocin's role in EGUS development and progression.

For more details, see: 

 

Botía, M., Muñoz-Prieto, A., Martínez-Subiela, S., Martín-Cuervo,^, M.,  Hansen, S. ,  Manteca, X. , Joaquín Cerón, J.,  López-Arjona, M.

Oxytocin in horse saliva: validation of a highly sensitive assay and a pilot report about changes in equine gastric ulcer syndrome. 

BMC Vet Res (2025) 21, 90 

https://doi.org/10.1186/s12917-025-04569-3

Behavioural signs of gastric pain

(c) Abby Thoriaty Dreamstime

 Researchers have identified distinctive behavioural signs that may indicate equine gastric discomfort.

Gastric ulcers are often believed to be the cause of a wide range of behavioural and performance issues in horses. Studies suggest that between 60% and 80% of horses across various disciplines experience gastric ulceration. However, a definitive diagnosis requires gastroscopy.

Are there specific behavioural indicators that reliably suggest gastric ulceration? Researchers at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center believe so.

In research published in Animals, Catherine Torcivia and Sue M. McDonnell explored this question. As part of their clinical assessments, they regularly analyse 24-hour video recordings of hospitalised horses to detect subtle signs of discomfort, or intermittent signs caused by heart or neurological problems, which might otherwise go unnoticed. Over the years, they suspected that certain behaviours were associated with gastric disease.

Their findings suggest that specific discomfort behaviours are strongly linked to gastric disease. These behaviours include frequent attention to the cranial abdomen—such as nuzzling, swatting, nipping, and/or a focused gaze on the abdomen caudal to the elbow—as well as deep abdominal stretching. These signs were often observed while horses were eating, drinking, or anticipating feeding.

To investigate this further, they conducted a study to evaluate how reliably these behaviours correlated with gastric disease. They reviewed clinical records of 30 cases where 24-hour video behaviour evaluations had been conducted alongside gastroscopic examinations.

Of the 30 horses studied, 26 were diagnosed with gastric disease—either gastric ulcers or gastric impaction. Gastric discomfort behaviours were observed in 24 of these 26 horses but were absent in all four horses without gastric disease. Among the six horses that did not display these behaviours, four had no abnormalities on gastroscopy, while two exhibited only mild lesions.

The researchers conclude that, although a larger study is needed to accurately estimate the sensitivity and specificity of these behavioural associations with gastric disease, the findings support their long-held clinical impression that gastric discomfort in horses has a recognisable behavioural signature.

For more details, see:

 

Torcivia, Catherine, and Sue M. McDonnell. 2025. 

Behavioral Signature of Equine Gastric Discomfort? Preliminary Retrospective Clinical Observations

Animals (2025) 15, no. 1: 88. 

https://doi.org/10.3390/ani15010088

Investigating injectable omeprazole for gastric ulcers

(c) Abby Koriaty Dreamstime.com

Gastric ulcers pose a significant concern in horses, particularly those engaged in high-
performance activities or those under stress. 

The horse’s stomach is divided into two distinct regions, the squamous and glandular mucosa. The upper (dorsal) portion of the stomach is covered by squamous epithelium. The glandular mucosa that lines the lower (ventral) portion of the stomach contains gastric glands that secrete hydrochloric acid, pepsinogen, histamine, mucous, and sodium bicarbonate. 

 

Omeprazole is commonly used, in conjunction with management changes, for treating gastric ulcers in horses. Classified as a 'proton pump inhibitor,' omeprazole functions by inhibiting the hydrogen-potassium adenosine triphosphatase enzyme system, usually known as the 'proton pump.' This enzyme system is found in the cells of the glandular mucosa that produce stomach acid. Omeprazole disrupts the normal operation of proton pumps, resulting in a reduction in stomach acid production.

 

Omeprazole is typically administered orally, using daily paste formulations or enteric-coated granules. An increasingly popular treatment for equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD) involves the weekly administration of an extended-release injectable omeprazole formulation (ERIO*) which is available in some countries.

 

Tania Sundra and her colleagues conducted a study to assess the impact of ERIO formulation treatment administered at 5- or 7-day intervals on ESGD and EGGD. They reviewed clinical records from Avon Ridge Equine Practice, Western Australia, covering gastroscopic examinations conducted from July 2020 to November 2021, identifying horses that had been treated with ERIO.

 

Gastroscopic images, anonymized and graded by a researcher unaware of the treatment group, were used for comparison. Univariable ordered logistic regression was employed to analyze responses to the two treatment schedules. 

 

The findings, indicating a higher proportion of EGGD healing with ERIO administered at 5-day intervals compared to 7-day intervals, were reported without an apparent rise in complications. However, no significant difference was observed in the proportions of ESGD healing between the two treatment regimens.

 

A detailed report of this study can be found in the Equine Veterinary Journal. The authors suggest that the use of ERIO at 5-day intervals might be more appropriate than the 7-day interval that is used currently.

 

 

For more details, see:

 

Five- versus seven-day dosing intervals of extended-release injectable omeprazole in the treatment of equine squamous and glandular gastric disease

Tania Sundra, Erin Kelty, David Rendle 

Equine Vet J (2024) Vol 56(1):51-58.

https://doi.org/10.1111/evj.13938

*Extended-release injectable omeprazole . BOVA Australia