Epizootiology and pathophysiology of bovine oriental theileriosis in Mizoram, India.

Bovine oriental theileriosis is an important tick-borne haemoprotozoan disease caused by Theileria orientalis. The present study was carried out to investigate the prevalence, associated risk factors, and haemato-biochemical and pathological alterations associated with naturally occurring T. orientalis infection in cattle, an emerging disease in Mizoram, India. A polymerase chain reaction (PCR) detection based cross-sectional study on the prevalence of T. orientalis infection in cattle was undertaken from June 2019 to January 2022. Blood samples were collected from the clinically infected crossbred cattle (n = 12) to examine the haemogram, and serum samples were used for evaluating biochemical profile and oxidant-antioxidant status. The diagnosis of T. orientalis infection in cattle was carried by microscopic blood smear examination and further confirmed by PCR. Haemogram and serum biochemical profile were evaluated by automated blood cell counter and clinical chemistry analyzer, respectively. Oxidant and antioxidant parameters were estimated by using commercially available assay kits. In the present study, PCR was found to be more sensitive than microscopic blood smear examination, and an overall prevalence of 7.29 % was recorded for T. orientalis infection by PCR assay. Tick infestation, uncemented floor, and absence of acaricidal treatment were found be potential risk factors for T. orientalis infection. Haemogram and serum biochemical findings revealed anaemia, thrombocytopenia, hypoproteinemia, elevated aspartate aminotransferase (AST) and blirubin levels, and azotemia. The mean values of superoxide dismutase (SOD), glutathione (GSH) and total antioxidant capacity (TAC) were significantly (P < 0.05) lower, whereas the mean value lipid hydroperoxide (LPO) were significantly (P < 0.05) higher in cattle infected with T. orientalis, suggesting oxidative stress. When total erythrocyte count (TEC) was correlated with LPO (r = -0.781, P < 0.01), it revealed a negative correlation, while in case of GSH (r = 0.744, P < 0.01), SOD (r = 0.794, P < 0.01), and TAC (r = 0.796, P < 0.01), a positive correlation was noticed. The correlation of oxidative stress indices with TEC suggested that erythrocyte peroxidation could play an important role in the pathogenesis of anaemia induced by T. orientalis infection. There are very few studies on the pathological aspects of T. orientalis infection in cattle. Thus, the outcome of the present study could add valuable information to the current existing knowledge about the disease.