Changes in Calprotectin (S100A8-A9) and Aldolase in the Saliva of Horses with Equine Gastric Ulcer Syndrome

SIMPLE SUMMARY: Equine gastric ulcer syndrome (EGUS) is a frequent disease that considerably reduces the quality of life of horses, while also affecting their physical performance, even when the disease is subclinical. In this study, we hypothesized that two analytes, calprotectin (CALP) and aldolase, could be measured in saliva with commercially available assays and be potential biomarkers of EGUS in horses. We investigated the changes in the salivary CALP and aldolase in 131 horses divided into 5 different groups: controls (healthy horses), with equine squamous gastric disease (ESGD), with equine glandular gastric disease (EGGD), with combined ESGD and EGGD, and horses with other intestinal pathologies but clinical signs similar to EGUS. The two assays were precise and accurate, and, in both cases, they showed differences between horses with EGUS and healthy horses, but they did not show significant differences between horses with EGUS and horses with other diseases. Our data showed that CALP has a high ability to differentiate between healthy horses and horses with EGUS. Therefore, it could have potential use as a biomarker since a value of CALP in the range of healthy individuals could indicate that the animal is not likely to have EGUS at gastroscopy. ABSTRACT: Equine gastric ulcer syndrome (EGUS) is a highly prevalent disease that affects horses worldwide. Within EGUS, two different forms have been described: equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD). The associated clinical signs cause detrimental activity performance, reducing the quality of life of animals. Saliva can contain biomarkers for EGUS that could be potentially used as a complementary tool for diagnosis. The objective of this work was to evaluate the measurements of calprotectin (CALP) and aldolase in the saliva of horses as potential biomarkers of EGUS. For this purpose, automated assays for the quantification of these two proteins were analytically validated and applied for detecting EGUS in a total of 131 horses divided into 5 groups: healthy horses, ESGD, EGGD, combined ESGD and EGGD, and horses with other intestinal pathologies. The assays showed good precision and accuracy in analytical validation, and they were able to discriminate between horses with EGUS and healthy horses, especially in the case of CALP, although they did not show significant differences between horses with EGUS and horses with other diseases. In conclusion, salivary CALP and aldolase can be determined in the saliva of horses and further studies are warranted to elucidate the potential of these analytes as biomarkers in EGUS.