SUBCELLULAR CHANGES IN THE TONSILS OF PIGS INFECTED WITH ACUTE AFRICAN SWINE FEVER VIRUS

A study of the pathogenesis of acute African swine fever (ASF) was car ried out in pigs inoculated with a highly virulent strain of ASF virus to determine the sequential development of the subcellular changes in a particular lymphoepithelial organ, the tonsil. The apoptosis of the lymphocytes and the inhibition of lymphocyte proliferation were the m ain changes that occurred in the tonsillar lymphoid structures, This m ay explain the early lymphopenia observed in acute ASF, Moreover, vasc ular changes, consisting of increased vascular permeability, activatio n of endothelial cells and loss of these cells, might have been the ca use of the characteristic haemorrhages found in the lymphoid organs du ring this disease, Virus replication has been observed in the epitheli al cells, fibroblasts and reticular cells beginning on day 5 post-infe ction, The activation of the endothelial cells, apoptosis of lymphocyt es, decreased lymphocyte mitosis and virus replication in non-mononucl ear phagocyte system (MPS) cells all occurred after an intense prolife ration and activation of the tonsillar macrophages and coincide with v irus replication, which occurs in the macrophages 5 days post infectio n.