Transmission Dynamics of Gilts Persistently Infected with Atypical Porcine Pestivirus

Atypical porcine pestivirus (APPV) is a pestivirus that infects swine and has been associated with congenital tremor (CT) in piglets in the field, as well as those born to experimentally infected sows. However, APPV has also been detected in swine of various ages without clinical signs. Experimental and field studies have demonstrated prolonged detection of viral RNA in serum, secretions, and tissues. For this work, nine gilts from a longitudinal APPV field study were selected based on birth in CT-positive litters and evidence of prolonged detection of virus in the sera. These six-month old animals were transported to a research facility for further sampling, breeding, and necropsy. The gilts were placed in contact with naïve animals for approximately one month at two different timepoints, prior to and during gestation, to assess transmission. After farrowing, litters were monitored for CT and tested for APPV. Following arrival, serum samples were PCR-negative for APPV; however, the gilts consistently tested positive in oral fluids and had detectable APPV in the cerebellum months later at necropsy. The gilts had a delayed humoral immune response, with the majority not seroconverting until approximately ten months of age. There were PCR-positive tissues and evidence of seroconversion in animals from both contact groups; however, none of the litters tested PCR-positive for APPV. These findings improve our understanding of the temporal dynamics and transmission potential of APPV infection and can help guide control measures to reduce viral spread.