Use of a swine bioassay and a RT-PCR assay to assess the risk of transmission of swine hepatitis E virus in pigs.

The objective of this study was to assess the risk of transmission of swine hepatitis E virus (swine HEV) to naïve pigs by inoculation with tissues or feces collected from pigs infected experimentally with swine HEV. Seventy-five, 3-week-old pigs were assigned randomly to 24 groups of 3-4 pigs and inoculated with homogenates of tissues (liver, heart, pancreas, or skeletal muscle) or a suspension of feces from swine HEV-infected pigs collected at 3, 7, 14, 20, 27, or 55 days post inoculation (DPI). Each inoculum was prepared as a 10% suspension (w/v) in PBS buffer and tested by a semi-quantitative RT-PCR for swine HEV RNA and by the swine bioassay. The inoculation route was intravenous for liver, heart and pancreas, and via stomach tube for skeletal muscle and fecal suspension. The liver homogenate inocula and feces collected at 3-7 and 14-20 DPI were positive for swine HEV RNA by RT-PCR. The pigs inoculated with liver homogenates collected at 3-7 and 14-20 DPI developed anti-HEV antibodies and swine HEV RNA was detected in their sera. Pigs inoculated with heart, pancreas, skeletal muscle homogenates or fecal suspensions failed to develop anti-HEV antibodies. These findings suggest that there is a potential risk of transmission of swine HEV via liver tissue from infected pigs in the early stages (3-20 DPI) of infection and the in vitro RT-PCR assay correlates well with the swine bioassay.