Bovine theileriosis is a protozoan disease caused by the intracellular parasite (Theileria spp.) transmitted by ticks and it is considered one of the most significant parasitic diseases, potentially endangering Egyptian cattle herd industry. The present study was conducted for a molecular survey of bovine theileriosis and its associated risk factors (season variations, geographical locations, breeds, age, sex, tick infestation, and acaricide applications) in three Egyptian governorates, Beni-Suef, Al-Faiyum, and Al-Minya for a year extended from December 2021 to November 2022, in addition, genetic diversity of Theileria isolates. A total of 961 cattle were examined for Theileria infection clinically, microscopically, and by Polymerase Chain Reaction (PCR) using 18S rRNA gene for piroplasms DNA detection, Theileria genus-specific primers of the small subunit of rRNA gene, and Theileria annulata specific primers of the Tams-1 gene. The prevalence rate of bovine theileriosis was 9.26%, and 11.86% using Giemsa-stained blood smear and PCR, respectively. All positive samples screened by Theileria genus-specific primers were positive for T. annulata when screened by the specific primers. Based on molecular screening, season, cattle breeds and acaricide applications were considered risk factors for T. annulata infection, while locality, age, sex and tick infestation had insignificant effects with the occurrence of the disease. A potential novel T. annulata haplotype based on the Tam-1 gene was identified with accession numbers OR364144 and OR915851. Therefore, T. annulata was the only Theileria species found and played a significant problem in the cattle population. This study could be the basis for future studies on unexplored regions and different animal species for well-structured prevention and control measures.

Keywords: Haplotype; PCR; Prevalence; Risk factors; Tam-1; Theileria annulata.