Detection of Theileria equi‎ in Baghdad Racing Horses Using ‎Hematological and ‎Molecular Assay

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Ahmed N ALani
Afaf A Yousif


The aim of this study was to investigate the prevalence of Theileria equi infection in racing horses in ‎‎Baghdad governorate, utilizing clinical signs, microscopic examination, molecular assays, and hematological tests to identify significant differences between infected and non-infected horses. Between January and December 2021, a total of 160 racing horses from three locations in Baghdad governorate (Al-Amiriya Equestrian Club, Arabian horses in Alzwraa Zoo, and Iraqi Equestrian School) were randomly selected for examination. Microscopic examination of blood smears revealed 11 positive samples for Theileria equi ‎‎(6.875%), while the results of the polymerase chain reaction assay targeting the 18S ribosomal RNA gene ‎‎confirmed 26 positives (16.25%). Sequenced amplicons and phylogenetic tree analysis ‎‎revealed a genetic similarity of 93.03–100% and 94-100% site coverage compared to many global countries' isolates. Interestingly, only 16 (61.5%) of the 26 infected horses showed mild to subclinical symptoms or were carriers of the disease without tick infestation. Hematological blood parameters showed non-significant differences between infected and non-infected horses, except for a decrease in packed cell volume (PCV) and hemoglobin (Hb) concentration, which caused anemia in 12 horses among the 26 molecularly positive cases ‎‎(46.15%). Of these cases, 6 horses (23.08%) had normocytic normochromic anemia, while 3 ‎‎(11.54%) cases each had normocytic hypochromic and microcytic hypochromic anemia. Notably, young horses (two years old) were more susceptible to infection (odds ratio ‎‎15.4) than those over six years old. Additionally, sex and breed did not show any significant correlation with equine theileriosis. In conclusion, this study detected Theileria equi infection in young racing horses in Baghdad. Clinically, most infected cases showed mild to asymptomatic signs accompanied by anemia. Molecular investigation revealed high genetic ‎‎similarity to isolates reported globally. These findings highlight the importance of implementing measures to control and prevent the spread of Theileria equi in racing horses in Baghdad and other regions. Further studies are warranted to better understand the ‎‎epidemiology, pathogenesis, and risk factors associated with equine theileriosis‎.


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N ALani, A., & A Yousif, A. (2023). Detection of Theileria equi‎ in Baghdad Racing Horses Using ‎Hematological and ‎Molecular Assay. The Iraqi Journal of Veterinary Medicine, 47(1), 52–59.


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