Oriental theileriosis, a tick-borne entity caused by the haemoprotozoan parasite Theileria orientalis, presumably a benign Theileria species appears to be an important disease problem in cattle nowadays. The present communication reports a fatal case caused by T. orientalis in a pregnant heifer from Northeast India. The animal, with history of high fever, inappetance, nervine symptoms followed by recumbency and nonresponsive to subsequent symptomatic treatment was brought to the outpatient unit of the author’sinstitute’s Clinical Complex for blood examination and further treatment on 3rd day of illness.Microscopic examination of blood smear followed by Polymerase Chain reaction (PCR) analysisconfirmed the presence of Theileria orientalis infection and involvement of Ikeda variant. Administrationof anti theilerial compound Buparvaquone at the terminal stage of illness was however unsuccessful andthe animal succumbed to infection within 8 hours of parasite specific treatment. Ulcers in abomasalmucosa, distended gall bladder, lung oedema, tarry colored sticky intestinal contents indicatinghemorrhage from abomasal ulcers were the important pathological findings observed at necropsy. On the basis of clinical symptoms, microscopic and molecular study along with postmortem findings, the cause of death of the pregnant heifer was attributed to be due to Theileria orientalis infection.
