Evaluation of Eosinopenia as a SIRS Biomarker in Critically Ill Horses

Simple Summary Eosinopenia has been used as a biomarker of systemic inflammatory response syndrome in critically ill humans. Horses are extremely prone to developing systemic inflammation in different conditions such as endotoxemia. It is for that reason that new biomarkers are needed in horses to rapidly identify the patients that require hospitalization in the intensive care units to minimize unnecessary expenses. The aim of this study was to evaluate eosinopenia as a potential marker of systemic inflammation and prognosis in horses. The results showed lower eosinophil counts in horses affected with systemic inflammation compared to the control group (p < 0.05). Horses with eosinopenia were less likely to survive, and hence, eosinophil count could be used as a marker of prognosis and disease. Systemic inflammatory response syndrome (SIRS) is a very common finding in critically ill patients. To accurately identify patients with SIRS and those who need intensive care, several markers have been evaluated, including cortisol, WBC or lactate. It is widely known that a stress leukogram includes eosinopenia as one of its main markers (neutrophilia, eosinopenia, lymphopenia and mild monocytes). It is known that cortisol concentration in plasma is the main stress biomarker and is strongly correlated with the severity of disease in horses. However, it is not possible to measure this parameter routinely in clinical conditions. Hence, in this study it was hypothesized that the eosinophil count could be a reliable parameter to identify critically ill horses. Horses included in this study were divided into three groups: Group A (sick horses received at the Emergency Unit which did not fulfil the criteria for SIRS), Group B (horses that meet two or more criteria for inclusion in the definition of SIRS) and a control group of healthy horses. In this study, horses with SIRS showed lower eosinophil counts than healthy horses. Moreover, non-surviving horses exhibited lower eosinophil counts than survivors. Eosinopenia could be used to identify horses with SIRS and can be useful as a prognostic marker.