Rat-associated hepevirus in European Norway and Black rat populations: a survey in 12 European countries

The rat-associated hepevirus, rat hepatitis E virus (HEV), was initially discovered in Norway rats (Rattus norvegicus) from Hamburg, Germany, and subsequently detected in rats from other cities in Germany and in rats from Vietnam, the US, Indonesia, China, Denmark and France. Norway rats from the US and Japan were also found to be infected with human pathogenic HEV-genotype 3 (GT3). A molecular survey was performed for Norway rats and Black rats (Rattus rattus) from Germany and eleven additional European countries using different hepevirus-specific reverse transcription-polymerase chain reaction assays. In total 508 rats were collected and analysed with an overall ratHEV prevalence of 12.4% (63/508), with a range between 4% to 22.4%. Positive rats were detected in eleven of 12 countries. RatHEV-RNA was detected in 13.8% (58/420) of Norway rats and 5.6% (5/88) of Black rats. Phylogenetic reconstructions indicated clustering of all European ratHEV sequences within designated ratHEV-genotype 1. The presence of multiple, well-separated sequence clades at the same sampling location might indicate the incursion of novel/different ratHEV strains into local Norway rat pop-ulations with a potential, parallel persistence of a local, ratHEV strain. This necessitates future studies on the population structure and potential immigration of individuals into existing rat populations and their association with ratHEV incursion. In addition, the finding of ratHEV infections in zoological gardens may allow future studies on the zoonotic potential of ratHEV based on the investigation of putative natural ratHEV transmission to non-human primates or animals like rabbits or goats.