CELL-FREE AND CELL-ASSOCIATED VIREMIA IN PIGS AFTER ORONASAL INFECTION WITH AUJESZKYS-DISEASE VIRUS

Nine pigs were examined for the presence of viremia during the first w eek after oronasal inoculation of 10(8.0) TCID50 Aujeszky's disease vi rus (ADV). Blood was taken at 1, 2, 3, 5 and 7 days post inoculation ( PI) and the presence of cell-free ADV in plasma and of ADV-infected mo nonuclear cells was examined by titration and by cocultivation with pe rmissive cells, respectively. The mononuclear cells of 6 of the 9 pigs , collected at 3 and 5 days PI were further separated into subpopulati ons of enriched monocytes and enriched lymphocytes. Both subpopulation s were cocultivated. Nasal secretions were collected from 4 of the 9 p igs for the determination of virus titers and interferon concentration s. Both infected mononuclear cells and cell-free ADV were demonstrated in 5 pigs, infected mononuclear cells only were found in 2 pigs, and neither cell-associated or cell-free ADV were detected in 2 pigs. Two of the 7 viremic animals were positive on one single day, 3 on 2 days, 1 on 3 days and 1 on 4 days. The number of infected cells was approxi mately 5 times higher in monocytes than in lymphocytes. The highest vi rus titers were present in those nasal fluids with the lowest alpha-in terferon concentration. A correlation between the titer of locally pro duced ADV in the nose and the presence of a viremia was not found. In conclusion, we can state that a viremia regularly occurs under both ce ll-free and cell-associated form after an oronasal inoculation of ADV and that monocytes are the most susceptible mononuclear cells.