A pathological study of the perisinusoidal unit of the liver in acute African swine fever.

African swine fever is an acute haemorrhagic disease of pigs which may serve as a model for the study of the pathogenesis of other viral haemorrhagic fevers. This paper describes an ultrastructural study of the sequence of lesions produced in the perisinusoidal functional unit of the liver of pigs inoculated with the Malawi '83 strain of African swine fever virus, which is classified as haemadsorbing and highly virulent. Virus replication was observed in Kupffer cells and monocytes from three days after inoculation, in hepatocytes and fat-storing cells at five and seven days after inoculation, and in sinusoidal endothelial cells at seven days after inoculation. Further observations included intravascular coagulation, which peaked at five days after inoculation, and fibroblast and myofibroblast transformation of fat-storing cells at seven days after inoculation. These results suggest that activated cells of the mononuclear phagocyte system may play a major role in this sequence of lesions and the possible role of the cytokines that may be released by these cells is discussed.