The growth of virulent African swine fever virus in pig monocytes and macrophages.

The replication of virulent African swine fever virus (ASFV) in cultures of monocytes and macrophages derived from pig bone marrow (PBM) and pig leukocyte (PL) cells was investigated by light microscopy, immunofluorescence, haemadsorption and infective virus release. Monocytes showed a high rate of infection and complete destruction within 2 to 3 days, whereas macrophages had only a very low level of infection and survived to form persistently infected cultures. These observations may explain the decrease in sensitivity of PBM and PL cells for ASFV assay after extended periods of incubation and suggest that the macrophage may be one of the cell types concerned with virus persistence in the pig.