Correlation between positivity for immunoglobulin A antibodies and viraemia of swine hepatitis E virus observed among farm pigs in japan

To evaluate the usefulness of detection of antibodies to hepatitis E virus (HEV) to screen for viraemic pigs, serum samples obtained from 1425 1–6-month-old pigs in Japan were tested for swine HEV RNA and IgG, IgM and IgA classes of anti-HEV antibody. Fifty-five (5 %) of the 1071 2–5-month-old pigs were positive for swine HEV RNA, but none of 218 1-month-old pigs or 136 6-month-old pigs had detectable HEV RNA. The prevalence of anti-HEV IgG among the viraemic pigs (67 %, 37/55) was similar to that among the non-viraemic pigs (55 %, 757/1370) and the prevalence of anti-HEV IgM among the viraemic pigs and non-viraemic pigs was 7 and 3 %, respectively. However, anti-HEV IgA was detected significantly more frequently among viraemic pigs than among non-viraemic pigs (55 vs 10 %, P<0·0001). These results suggest that anti-HEV IgA is more useful than anti-HEV IgM to screen for viraemic pigs.