Malignant ovine theileriosis in a sheep flock

A sick and 3 dead sheep belonging to 12–16 months age group from a sheep flock were presented for clinical and post-mortem examination. Sick sheep exhibited pyrexia, depression, pale mucous membrane, severe respiratory distress, enlarged lymphnodes and tick infestation. Haematology revealed decreased haemoglobin, RBC countand PCV. Blood smear exhibited numerous Theileria lestoquardi in erythrocytes. Fine needle aspiration biopsy of lymph nodes depicted Koch's blue bodies. On post-mortem examination of three carcasses, enlarged liver with rounded edges and yellowish discoloration having multifocal necrosis was observed. Gall bladder contained yellowish bile and their mucosa were severely icteric. Notably, abomasal mucosa exhibited presence of few ulcers, which is rare lesion in ovine theileriosis. Microscopically, liver showed vacuolar degeneration, necrosis and thrombi formation in the central vein and Koch's blue bodies in the lymphocytes. Kidneys revealed necrosis and desquamation of tubular epithelium. Based on characteristic features, the disease was diagnosed as theileriosis in sheep.