Clinical and pathological features of viral haemorrhagic disease of rabbits and the European brown hare syndrome.

The authors review the clinical, macro- and microscopical features, and pathogenesis of viral haemorrhagic disease (VHD) of rabbits and the European brown hare syndrome (EBHS). The two diseases share similar clinical and pathological manifestations involving an acute syndrome, sometimes accompanied by nervous and respiratory symptoms and epistaxis, and in all cases by severe hepatic damage and multifocal haemorrhages leading to fatal shock. The hepatic lesions (necrosis and inflammation) result from direct cytolytic and indirect microthrombotic effects of the causal agent. Endothelial lesions and a primary or secondary defect of coagulation factors are possible causes of the haemorrhagic syndrome. Typical lesions consist of necrotic hepatitis and congestion, haemorrhaging and oedema of the lungs and trachea. The histological and ultrastructural alterations of the liver are similar to those found in certain cases of acute fatal hepatitis in man. The high correlation between histologically typical hepatic findings and immunohistochemistry and immunoelectron microscopy is of diagnostic value. Both microscopic lesions and pathogenesis favour the unifying definition of "infectious necrotic hepatitis of Leporids" for the two disease entities.