Rat Hepatitis E Virus (RHEV) in Mus musculus and Rattus norvegicus in Northwestern Italy.

Hepatitis E virus (HEV) represents a major public health concern. Beyond the main zoonotic genotypes HEV-3 and HEV-4, with pigs and wild boars recognized as the primary reservoirs of infection, a genetically distinct hepevirus of rodent origin (species Rocahepevirus ratti, genotype C1) (rat HEV, RHEV) has recently been implicated in human hepatitis cases worldwide. Although several risk factors have been proposed, contact with rats has been documented in one human case only, and the sources and transmission routes of RHEV remain largely unclear. Of interest, RHEV RNA has recently been detected in farmed pigs, highlighting livestock environments as potential interspecies transmission interfaces. In light of these findings, we performed a molecular investigation for RHEV in rodents captured on farms raising different livestock species in Northwestern Italy (Piemonte region). A total of 98 rodents, collected on 32 livestock farms, were tested for RHEV by a combined molecular approach based on RHEV specific real-time reverse transcription (RT)-PCR assay and a pan-hepevirus heminested RT-PCR. Positive samples were further processed to attempt full-genome amplification. RHEV RNA was identified in a Norway rat (Rattus norvegicus) and in house mice (Mus musculus), with detection rates of 16.6% (1/6; 95% CI: 0.41-64.1) and 7.0% (6/86; 95% CI: 2.6-14.5), respectively. The positive rodents were captured in five livestock farms, raising cattle, goats, and poultry, located across three municipalities. The nearly full-length genome of a rat strain (RHEV/Rattus norvegicus/38129-22/ITA) was reconstructed. Pairwise nucleotide alignment showed high genetic relatedness of RHEV/Rattus norvegicus/38129-22/ITA with sequences previously identified in rodents and human patients, including those from European countries. The identification of infected rodents in livestock farms highlights RHEV circulation in rural environments, where interactions among rodents, domestic animals, and humans may be facilitated. Additional studies are necessary to elucidate RHEV transmission dynamics and assess public health implications.