Molecular characterization and prevalence of hepatitis E virus in Swedish wild animals

Abstract: Observation of chronic hepatitis E virus (HEV) in immunosuppressed patients, and unexplained high hepatitis E virus (HEV) prevalence in the human population raises public health concern. The aim of this thesis is to molecular characterize and investigate the prevalence of HEV in Swedish wild life and their association with HEV transmission to humans. A novel virus was detected in a sample from a Swedish moose (Alces alces). The genome was highly divergent with sequence identity of 30-60% to other HEVs. Genome sequence and phylogenetic analysis showed closest relationship with HEV genotypes1-7 (gt1-7). In addition, three open reading frames (ORFs) was also detected, and all these observed properties suggested the virus as a member of the Hepeviridae family. Markers for ongoing (HEV RNA) and/or past HEV infection (anti-HEV) was demonstrated in 67 (29%) of 231 Swedish moose samples collected from various Swedish provinces. Thus, moose are frequently infected with HEV. Its closest similarity with the HEV gt1-7 group, which includes strains that also infects humans, may indicate a potential for zoonotic transmission of this HEV. A survey detected HEV markers in the wild life, which included samples from wild boars (Sus scrofa) and different deer species, fallow deer (Darna darna), red deer (Cervus elaphus), roe deer (Capreolus capreolus) and moose (Alces alces). These markers were ongoing and/or past infections, and were found in 53 (22%) out of 245 animal samples. The viral nucleic acid sequences strains were sequenced and compared with autochthonous Swedish human HEV cases, of whom three were found infected with strains similar to wild boar strains. These results indicate that Swedish wild animals are often infected with HEV and may be an important source of HEV transmission to humans who come into contact with wild animals or eat game meat. The introduction of a single amplicon PCR of near complete HEV genomes enabled the identification of possible virulence marker, and the detection of possible recombination events between Swedish swine and wild boar, and that there may have been zoonotic transmission of HEV strains between Spain and France.