Commercial feed containing porcine plasma spiked with African swine fever virus is not infective in pigs when administered for 14 consecutive days

Abstract

The objective of this study was to determine if commercially collected liquid porcine plasma contaminated with African swine fever virus (ASFV) and fed for 14 consecutive days would infect pigs. Commercially collected liquid porcine plasma was mixed with the serum from an ASFV experimentally infected pig. To simulate the potential of pigs slaughtered being ASFV viremic but asymptomatic and passing antemortem inspection, the ratio of liquid plasma from healthy animals to serum from an ASFV infected pig used in this study represented 0.4% or 2.0% of the pigs slaughtered being viremic (Studies 1 or 2, respectively). The contaminated liquid plasma was mixed on commercial feed and pigs were fed for 14 consecutive days providing to each pig 104.3 or 105.0 TCID50 ASFV daily (Studies 1 or 2, respectively). Pigs were observed for an additional 5 or 9 days (Studies 1 or 2, respectively). In both experiments, the pigs did not become infected with ASFV during the 14d feeding period or during the subsequent observation period. In these experiments, unprocessed liquid plasma contaminated with ASFV mixed on commercial feed and fed for 14 consecutive days did not infect pigs. From our results we can conclude that the infectious dose of ASFV on feed is much higher than that previously reported, at least with ASFV-spiked raw plasma.