Molecular Detection and Phylogenetic Analysis of

Indonesia routinely imports buffalo to meet domestic meat demand, however outbreaks of theileriosis caused by Theileria orientalis have been reported in Vietnam among imported buffalo. Early detection is crucial in Jambi Province, which receives large consignments of buffalo meat. Theileriosis is an intracellular protozoan infection caused by Theileria sp., significantly affects livestock health and productivity. Information on detection and genetic diversity of Theileria sp. in Indonesian buffalo remains scarce. This study aimed to identify Theileria sp. from imported buffalo arriving in Jambi and to analyze their phylogenetic relationship with isolates from other regions using microscopic examination, PCR, and 18S rRNA sequencing. A total of 38 blood samples were examined microscopically and tested by PCR targeting the 18S rRNA gene, followed by Sanger sequencing for phylogenetic analysis. Microscopic examination did not reveal intraerythrocytic piroplasms, whereas PCR confirmed infection in two samples, yielding an prevalence of 5.26%. Phylogenetic reconstruction using the maximum likelihood method demonstrated that Jambi isolates shared high nucleotide homology and clustered with T. orientalis from Thailand and T. buffeli from Myanmar, Vietnam, and India, supported by a bootstrap value of 85%. These findings suggest the possibility of transboundary dissemination of T. orientalis genotypes through livestock trade. This study contributes to understanding the distribution and genetic relationship of T. orientalis in buffalo imported into Indonesia and provides useful insights for epidemiological studies.