PURPOSES: This study aimed to determine the prevalence of Theileria equi (T. equi) and Babesia caballi (B. caballi) in racing horses in Erbil Province, Iraq, and to assess the associated hemato-biochemical changes in infected animals. METHODS: A total of 196 horses, including 155 clinically healthy and 41 clinically suspected infected animals, were examined using Giemsa-stained blood films and PCR to determine the prevalence rates. Additionally, the hemato-biochemical parameters of infected horses were compared to a non-infected control group (n = 10). RESULTS: The prevalence of T. equi and B. caballi was determined using two diagnostic methods. Giemsa-stained blood smear analysis revealed prevalence rates of 15.8% (31/196) for T. equi and 5.1% (10/196) for B. caballi. In comparison, conventional PCR targeting the 18 S rRNA gene detected higher prevalence rates of 22.44% (44/196) for T. equi and 8.2% (16/196) for B. caballi. The prevalence of T. equi was significantly higher than that of B. caballi (P <
0.002). Infected horses exhibited significant hematological alterations, including microcytic anemia, with notable reductions in RBCs, Hb, and PCV, along with increased WBCs, lymphocytes and basophils compared to the healthy control group. Biochemical analysis revealed significant increases in AST, ALT, ALP, and total serum bilirubin, and decreases in total serum protein, albumin, calcium, and glucose in infected horses. CONCLUSION: These findings highlight the urgent need for heightened awareness, effective diagnostic methods, and targeted treatment strategies to combat equine piroplasmosis among racing horses in Erbil Province, Iraq.