Special section on diseases of the equine gastrointestinal tract

Although there has been substantial progress in the diagnosis of gastrointestinal (GI) diseases of horses over the past few decades, diseases of the GI tract remain the most important cause of morbidity and mortality in horses. The hallmark clinical sign of GI disease is colic (abdominal pain), which can be classified as anatomical and/or functional. ⁹ Inflammatory conditions, which are among the most common diseases of the GI tract in horses, generally result in diarrhea. Other diseases of the GI tract include gastric ruptures and/or intestinal displacements, and the less frequently diagnosed dysautonomias. All diseases of the GI tract usually demand intensive diagnostic screening and treatment.^4,8 We prepared this special JVDI section in an attempt to compile some of the most significant and recent advances in the understanding of equine GI disease, which we hope will be helpful to diagnosticians.

Several infectious and noninfectious causes of diseases of the GI tract in horses are well characterized.^6,10 However, an etiologic agent remains undetermined in a large proportion of cases (~60%).^1,3,6 Extensive investigative efforts have aimed to better understand the intricate nature and pathogenesis of GI tract diseases in horses. This is particularly important in the development of new and better diagnostic methods and techniques. Given that many gross and microscopic lesions of the GI tract of horses can be very similar regardless of etiology, ⁷ current diagnostic approaches commonly require the use of ancillary tests. ¹⁰ Improving the sensitivity and specificity of current diagnostic tools and discovery of novel biomarkers may be key areas for future research.

Special attention has been directed to the study of the normal intestinal microbiota of horses, particularly in the context of microbial diversity. Disturbances of the intestinal microbiota have been well-documented in conditions such as Crohn disease, inflammatory bowel disease and colitis in humans, and in cases of undifferentiated colitis in horses.^2,5 In some circumstances, microorganisms that are usually considered part of the microbiota of normal horses can proliferate and cause disease. Determining the role of this otherwise normal flora in GI diseases poses a challenge that has not been completely resolved. We look forward to the continued unravelling of the complexities of the pathogenesis and diagnosis of GI disease in horses.