Molecular Detection of Bovine Theileria Parasites in Carrier Cattle

A total of 200 blood samples were collected from apparently healthy crossbred cattle of different age group (3-8 years) maintained in organized and unorganized farms in and around Patna including the Institutional Livestock Farm Complex, BASU, Patna. The study was conducted during January 2024–December 2025. The blood samples were subjected to laboratory screening for Theileria infection in apparently healthy cattle using blood smear examination and polymerase chain reaction (PCR). The diagnostic sensitivity of PCR was also compared to conventional detection in blood smears by light microscopy. Microscopic examination of blood smears and PCR analysis confirmed Theileria infection in 17 (8.5%) and 28 (14%) of the apparently healthy cattle. Among the PCR-positive cattle, 25 cattle (12.5%) were found positive for T. annulata, whereas 3 cattle (1.5%) were found positive for T. orientalis. Further, T. annulata is the predominant principal etiological agent of theileriosis in carrier cattle in the study region, whereas infections caused by T. orientalis also exist and seems to be comparatively uncommon. However, it is essential to understand the distribution pattern T. orientalis in different agro-climatic conditions that could help us to understand the severity associated with these species and design their control strategies. Considering blood smear as the reference test, PCR showed a sensitivity of 100% (95% CI: 80.5–100%) and specificity of 94% (95% CI: 89.5–96.9%). The high sensitivity indicates that PCR is highly effective in detecting theileria infection in carrier cattle, while the high specificity suggests that it accurately identifies non-infected animals. From this study, it can be concluded that the better sensitivity and specificity of PCR assay could be a better option than microscopic examination to precisely determine the carrier state of theileriosis in cattle.