Evaluation of Blood Biochemical Parameters and Ratios in Piroplasmosis-Infected Horses in an Endemic Region

Simple summary: Equine piroplasmosis (EP) is a tick-borne disease affecting equids (horses, donkeys, and mules) worldwide. This parasitic disorder has important health and economic impacts on the equid industry. Diagnosis is reached either by direct detection of the parasites (Babesia caballi, Theileria equi, or Theileria haneyi) in the bloodstream (PCR or blood smear) or by indirect methods (serology). However, it is unknown if other simpler and faster techniques, such as a biochemical profile, could help clinicians to identify this disease. In this study we describe biochemical differences between non-infected and EP-infected horses and evaluate the ability of these biochemical parameters and ratios to predict EP status.

Abstract: Equine piroplasmosis (EP), caused by Theileria equi and Babesia caballi, is a worldwide tick-borne disease with severe economic, commercial, and sanitary implications for equids. Although diagnosis is based on direct (blood smear or PCR) or indirect (serology) methods, these techniques are expensive, laborious, and false-negative and false-positive results can be yielded. Biochemistry blood profiles are routinely performed in horses. Biochemical parameters and ratios could be a reliable complementary diagnostic tool to assist clinicians in EP diagnosis, mainly in endemic areas, or for discarding similar disorders (piro-like diseases) and prioritizing specific diagnostic testing. This study describes the changes induced by EP infection in blood biochemical parameters and common and novel biochemical ratios in horses. EP-infected horses showed increased serum total and indirect bilirubin, triglycerides, and GLDH concentrations and decreased sodium concentrations compared to non-infected animals. These findings could be linked to hemolysis, diminution of athletic performance, and liver inflammation due to oxidative stress damage. While molecular methods remain the gold standard for EP diagnosis, a complete biochemical profile and ratios could provide valuable complementary information to enhance the diagnostic accuracy of piroplasmosis in horses.