MYOCARDITIS ASSOCIATED WITH THEILERIA SPP. IN CALVES

Two 3-week-old Limousin x Retinta calves from extensive farms in the s outh of Spain died suddenly. Microscopic examination of the spleen and lymph nodes revealed an intense lymphoid proliferation; the germinal centres were prominent and were surrounded by areas of haemorrhage. Pa rasitic forms, similar to Koch's bodies, mere observed in only a small number of lymphoid cells and macrophages. In the myocardium a severe myocarditis mas found. Inflammatory cells were in close contact:with d amaged myocytes, sometimes surrounding fragments of cells. In some are as the vessels had intraluminal deposits of fibrin. The endothelial da mage and thrombosis may have contributed to the damage observed in the myocytes, together with the cytotoxic mechanism associated with the p resence of an intense inflammatory infiltrate. The active multiplicati on of parasites may be due to the age of the animals and their breed, since they are not an autochthonous breed and present low resistance t o infection.