High HEV presence in four different wild boar populations in East and West Germany

Abstract

Swine Hepatitis E virus (HEV) can be transmitted from pigs to humans causing hepatitis. A high prevalence of HEV in wild boar populations is reported for several European countries, but actual data for Germany are missing. During the hunting season from October to December 2007 liver, bile and blood samples were collected from wild boars in four different German regions. The samples were tested for HEV RNA by quantitative PCR (qPCR) and anti-HEV IgG antibodies by two different ELISAs and a Line immunoassay. A seroprevalence of 29.9% using ELISA and 26.2% in the Line immunoassay was determined. The seroprevalence rate varied greatly within the analyzed regions. However, qPCR analysis revealed a higher prevalence of 68.2% positive animals with regional differences. Surprisingly, also adult wild sows and wild boars were highly HEV positive by qPCR. Compared to liver and serum samples, bile samples showed a higher rate of positive qPCR results. Sequencing and phylogenetic analysis of a 969 nt fragment within ORF 2 revealed that all isolates clustered within genotype 3 but differed in the subtype depending on the hunting spot. Isolates clustered within genotypes 3i, 3h, 3f and 3e. Within one population HEV isolates were closely related, but social groups of animals in close proximity might be infected with different subtypes. Two full-length genomes of subtypes 3i and 3e from two different geographic regions were generated. The wild boar is discussed as one of the main sources of human autochthonous infections in Germany.

Introduction

Four major genotypes can be differentiated in the genus Hepatitis E virus (HEV) within the family of Hepeviridae (Emerson and Purcell, 2007). Europe has long been considered to be non-endemic for HEV. However, in recent years an increasing number of autochthonous HEV cases were reported across Europe, and a close genetic relationship between these human-derived HEV sequences and porcine HEV isolates was demonstrated (Banks et al., 2004, van der Poel et al., 2001). Genotypes 3 and 4 are mainly found in industrialized countries. HEV isolates from sporadic acute human cases in these countries show a high genetic similarity to isolates from animals, especially from pigs (Goens and Perdue, 2004, Meng et al., 1997). For the years 2001–2007, 311 human cases of acute hepatitis E were reported in Germany, 142 (45.7%) of these infections were most likely acquired in Germany (Robert Koch-Institut, 2008). A case–control study about the risk of acquiring an HEV infection in Germany determined that the main risk factor was consumption of offal and meat from wild boars (Wichmann et al., 2008). While several studies across Europe detected a high prevalence of anti-HEV IgG antibodies and HEV RNA in wild boars and domestic pigs within all age groups (de Deus et al., 2008, Martelli et al., 2008, McCreary et al., 2008, Rutjes et al., 2007, Seminati et al., 2008), an HEV RNA prevalence of only 5% was found in serum samples collected from wild boars in north-eastern Germany in the late 1990s (Kaci et al., 2008). The main object of this study was to determine the actual prevalence of HEV genome and anti-HEV antibodies in wild boar populations in four different regions in Germany. Together with data on the geographical distribution of the particular hunting spots, a comparison of the endemic situation in several different wild boar populations becomes possible. Bile, liver and serum samples were collected and analyzed by quantitative PCR for HEV virus load. Sequencing and phylogenetic analysis were performed to determine the respective HEV geno- and subtype, and data obtained were compared to isolates found in other European countries. Investigations on the molecular epidemiology of HEV in different wild boar populations might help to assess the potential risk of zoonotic transmission of HEV from wild boars to humans.