Haematological and histological bone marrow findings in experimental classical swine fever

Aiming to shed more light on the pathogenesis of acute haemorrhagic diathesis in Classical Swine Fever (CSF), studies on hemostatic parameters were performed to evaluate blood coagulation pathways as well as determinations of blood cells counts with special emphasis on platelets in 16 pigs experimentally infected with the classical swine fever virus and in four control pigs. The aforementioned studies were complemented with histological evaluation of bone marrow of the same animals. In this study no significant changes were determined in the variables of intrinsic and extrinsic coagulation pathways, however, a significant reduction of platelet counts was detected starting at the third day post infection. The histological findings consisted in swelling and vacuolation of megakaryocytes observed in the bone marrow at the second day post infection, at four days post infection the megakaryocytes were necrotic. Other outstanding changes were detected in the vascular endothelium after the third day post infection, consisting in severe swelling and necrosis of endothelial cells. Thus, thrombocytopenia and endothelial damage are considered the basic causes of haemorrhagic diathesis. It is presumed that thrombocytopenia results from a direct viral damage to megakaryocytes. Coagulation disorders, at least in early stages of the disease, are not involved as causative factors of haemorrhagic diathesis.