Co-Circulation of Different Hepatitis E Virus Genotype 3 Subtypes in Pigs and Wild Boar in North-East Germany, 2019

Abstract

Hepatitis E is a major cause of acute liver disease in humans worldwide. The infection is caused by hepatitis E virus (HEV) which is transmitted in Europe to humans primarily through zoonotic foodborne transmission from domestic pigs, wild boar, rabbits, and deer. HEV belongs to the family Hepeviridae, and possesses a positive-sense, single stranded RNA genome. This agent usually causes an acute self-limited infection in humans, but in people with low immunity, e.g., immunosuppressive therapy or underlying liver diseases, the infection can evolve to chronicity and is able to induce a variety of extrahepatic manifestations. Pig and wild boar have been identified as the primary animal reservoir in Europe, and consumption of raw and undercooked pork is known to pose a potential risk of foodborne HEV infection. In this study, we analysed pig and wild boar liver, faeces, and muscle samples collected in 2019 in Mecklenburg-Western Pomerania, north-east Germany. A total of 393 animals of both species were investigated using quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR), conventional nested RT-PCR and sequence analysis of amplification products. In 33 animals, HEV RNA was detected in liver and/or faeces. In one individual, viral RNA was detected in muscle tissue. Sequence analysis of a partial open reading frame 1 region demonstrated a broad variety of genotype 3 (HEV-3) subtypes. In conclusion, the study demonstrates a high, but varying prevalence of HEV RNA in swine populations in Mecklenburg-Western Pomerania. The associated risk of foodborne HEV infection needs the establishment of sustainable surveillance and treatment strategies at the interface between humans, animals, and the environment within a One Health framework.

Keywords: HEV-3; Hepeviridae; One Health; genotype; reservoir; subtype; transmission.

Figure 1

Number of pigs and wild boars collected per month (blue and green column, respectively) with the respective number of HEV RNA-positive liver (orange bar) and corresponding prevalence rates (red dots). Animals were sampled in 2019 in Mecklenburg-Western Pomerania, Germany.

Figure 2

Phylogenetic relationship of HEV sequences from domestic pig and wild boar livers or faeces (MWP2019-385). The phylogenetic tree is based on the 250 nucleotide ORF1 region of HEV (nucleotide positions 127–376 of reference sequence FJ705359). The tree is drawn to scale, as the evolutionary distances used to derive the phylogenetic tree. The sequences retrieved from the NCBI GenBank are given with accession numbers. The HEV sequences obtained in this study from pigs are in red, sequences obtained from wild boar are in orange. Reconstruction of phylogenetic tree using Maximum Likelihood method with 500 bootstrap iterations. Bootstrap values >70 are annotated.