Pathological changes in the renal interstitial capillaries of pigs inoculated with two different strains of african swine fever virus

Summary African swine fever is a viral disease of pigs characterized predominantly by haemorrhagic lesions. This paper reports the lesions observed in the renal interstitial capillaries of pigs inoculated with African swine fever virus strains of differing virulence: the Malawi'83 strain (haemadsorbent and highly virulent) and the Dominican Republic'78 strain (haemadsorbent and moderately virulent). In pigs infected with the Malawi'83 strain, petechial haemorrhages and microhaemorrhages were observed 5 days after inoculation and lesions were evident in the renal capillaries. Signs of phagocyte activation were noticeable in endothelial cells, with enlarged fenestrations and even loss of endothelium, leaving the basement membrane of the vessels exposed. Platelet plugs and microthrombi were also observed in these vessels. At 7 days after inoculation these lesions had intensified, and were accompanied by virus replication in the endothelial cells. In pigs infected with the Dominican Republic'78 strain, haemorrhages were more abundant and more extensive, and although no endothelial cell lesions were observed, there was intense vasodilation with diapedesis of erythrocytes.