Evaluation of antioxidant status and oxidative stress in sheep experimentally infected with Anaplasma ovis

Anaplasma ovis infections can cause severe anemia in the acute phase of the disease. In order to investigate the alterations of erythrocyte protective antioxidant mechanisms associated with anemia in sheep experimentally infected with A. ovis, 100 ml heparinized blood was collected from splenectomised sheep that showed 6% A. ovis parasitemia. Inoculums of 20 ml blood were administered intravenously to five male sheep without any blood parasite. Parasitological and haematological changes and the activities of erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) were studied in experimentally infected animals on the 0-38 post infection days. Parasitemia increased significantly with the progress of infection and reached its maximum level on day 15 of the experiment. From this point to day 38, there was a gradual decline in parasitemia. A significant decrease in PCV, RBC and Hb concentration was evident coincidentally with peak parasitaemia in the infected sheep. On post infection day 15, the activities of all enzymes increased, the changes being significant for SOD activity. There was a significant positive correlation among parasitemia and the activities of erythrocyte SOD (r = 0.644, P<0.0005) and CAT (r = 0.424, P<0.05). Glutathione peroxidase activity declined significantly between post infection days 23-38. From the present study, it can be concluded that oxidative stress has an important role in anemia induced by anaplasmosis in sheep. It seems that SOD is a useful indicator of oxidative stress caused by A. ovis infection, due to its constant increasing means in the course of the disease.