Hepatitis E virus (HEV) infection among pigs in Poland: an assessment of the prevalence on commercial swine farms

Abstract

Hepatitis E is a zoonotic infection related to consumption of virus-containing food of pig origin. Pigs are a natural reservoir of hepatitis E virus (HEV), and infected animals can enter the food chain. The study evaluated the prevalence of HEV infections in pigs raised on 30 commercial pig farms in Poland. Six hundred pooled samples of pig faeces were collected from fatteners (440), gilts (69) and dry sows (91). For HEV detection a one-step real-time reverse-transcription PCR (real-time RT-PCR) method with an incorporated target-specific internal amplification control was used. Subtype identification of the detected HEV strains was based on amplification and phylogenetic analysis of the open reading frame (ORF) 2 region in the virus genome. Viral RNA was detected in 161 (26.8%; 95% confidence interval [CI]: 23.3–30.6) samples of pooled pig faeces. Fattener pigs were by far the most prevalently infected (35.9%; 95% CI: 31.4–40.6; odds ratio [OR] = 18.7, 95% CI: 4.9–159.6), and gilts were markedly less so (2.9%; 95% CI: 0.3–10.1; OR = 0.05, 95% CI: 0.006–0.20). HEV-positive pigs were raised on fattening units (OR = 1.6, 95% CI: 1.1–2.4) and farrow- to-finish farms (OR = 0.6, 95% CI: 0.4–0.9) without any differences in prevalence of infections associated with farm type (χ2 = 2.4, p<0:121). Phylogenetic analysis of the detected pig HEV strains affiliated them to the HEV-3c, 3i, 3e and 3f subtypes. Strains of the HEV-3i subtype dominated on farrow-to-finish farms (χ2 = 33.4, p<0:001), while 3f strains did so on fattening farms (χ2 = 19.1, p<0:001). The results evidence HEV mainly being prevalent in fattening pigs at the age of 5–6 months. Virus presence in these animals could pose a food-related risk of HEV infection when they reach slaughter age.