Abstract
Twelve pigs were inoculated with a highly virulent strain of hog cholera virus (HCV) to study viral infection of megakaryocytes in the bone marrow and spleen. Immunohistochemical and ultrastructural examination revealed HCV infection in a small proportion (2.5-9.0%) of these cells from the 2nd to the 9th day after inoculation, at which time the experiment was terminated. Megakaryocyte infection accounts for the presence of viral antigens in platelets. The latter may represent a passive vehicle for spreading the virus in the animal.