No Link Between Glandular Gastric Ulcers and Equine Herpesviruses

In humans, herpesviruses are associated with gastric ulcers, and stress plays a critical role in their development. In contrast to humans, researchers investigating herpesviruses in horses found no association between the presence of the equine herpesviruses-2 and -5 and equine glandular gastric disease (EGGD).^*

Lesions in the glandular or lower region of the stomach occur commonly, with affected horses presenting with behavior changes, poor performance, and variable other clinical signs. The underlying cause of EGGD remains unknown but could result from the failure of natural gastric defenses. Like humans with stress-induced peptic ulcers, stress may be a contributing factor for EGGD. Further, the equine herpesviruses-2 and -5 may also be linked to glandular ulcers.

To determine if a link between those herpesviruses and EGGD exists, horses with and without EGGD were identified via gastroscopy, and samples of gastric tissue were collected. Researchers retrieved healthy and diseased tissue in the pyloric region of the stomach lining during gastroscopy.

In total, 29 horses were included in the study. Eleven horses were considered normal, having no evidence of EGGD or equine squamous gastric disease (ESGD), 12 horses were diagnosed with only EGGD, and six horses had both EGGD and ESGD.

All biopsies were analyzed for viral genetic material (both DNA and RNA). Equine herpesviruses -2 and -5 were frequently identified in the studied horses. Specifically, all samples were positive for equine herpesvirus-2, and all but two horses were positive for equine herpesvirus-5.

Importantly, normal horses had higher viral loads of both equine herpesvirus-2 and -5 than horses with EGGD.

“This finding is in direct contrast to the researchers’ hypothesis and what is reported in humans, where a link between herpesvirus and peptic ulcers exists,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research nutrition advisor.

Additional studies are needed to determine the underlying cause of EGGD, a prevalent condition in horses.

“Unlike squamous disease, treating horses with antacids such as the proton pump inhibitor omeprazole, is not always effective. Once a better understanding of the pathophysiology of EGGD is attained, improved targeted therapies can be developed and initiated,” explained Whitehouse.

Currently, treatment options for glandular disease include omeprazole, sucralfate, misoprostol, and nutritional management. In Australasia, look for Sucralox.

“Further, reducing stress is a key part of managing horses with EGGD, requiring each situation to be assessed individually. Several practices are known to support horses with glandular disease, including providing at least two days of rest days after exercise, reducing the number of handlers, and maximizing time with herdmates in environments that allow interaction, such as mutual grooming,” shared Whitehouse.

Nutritionally, it may be beneficial to supplement the diets of horses with EGUS with long-chain omega-3 fatty acids to help support a healthy immune system and address potential sources of chronic inflammation.

“Fish oils, such as EO-3, are rich sources of both long-chain omega-3 fatty acids, EPA and DHA,” Whitehouse said.

For more information on EGGD, read “Squamous and Glandular Gastric Ulcers: New Treatment Options,” in the proceedings of the 2024 Equine Health and Nutrition Conference.

^*Thompson, R.N., E. Pearson, S.P. McDonough, H. Iannitti, G.R. Van de Walle, H. Banse, G.A. Perkins, and J.E. Tomlinson. 2024. Equine gamma herpesvirus presence and viral load are not associated with equine glandular gastric disease. American Journal of Veterinary Research:0282.