Rat Hepatitis E Virus in Norway Rats, Ontario, Canada, 2018–2021

H epatitis E virus (HEV) is a nonenveloped, single- stranded, positive-sense RNA virus within the family Hepeviridae, subfamily Orthohepevirinae, which is divided into 4 genera: Paslahepevirus, Rocahepevirus, Chirohepevirus, and Avihepevirus (1).Human hepatitis E is primarily caused by Paslahepevirus balayani (genotypes 1-4), and infection generally causes an acute, self-limiting disease, but severe and chronic hepatitis and extrahepatic manifestations can occur in immunocompromised patients (2).Paslahepevirus balayani genotypes 1 and 2 are endemic in developing countries, circulating in humans and transmitted primarily via the fecal-oral route through contaminated drinking water.Sporadic cases of hepatitis E infection caused by zoonotic transmission of HEV (Paslahepevirus balayani genotypes 3 and 4) are increasingly reported in industrialized countries (3).Infections are acquired through direct contact with infected animals, environmental contamination with animal feces, and foodborne transmission from eating undercooked pork, venison, and wild boar meat (3).Additional HEV variants have been reported in a diversity of animal species, and zoonotic transmission from animal reservoirs is a growing public health concern.Norway rats (Rattus norvegicus) have been shown to carry swine HEV (Paslahepevirus balayani genotype 3) and are natural reservoirs of HEV variants within the species Rocahepevirus ratti genotype C1 (rat HEV) (4).Since it was first detected in Germany in 2010, rat HEV has been identified in Norway rats from the United States, China, Vietnam, and 13 countries in Europe (5).Recently, cases of acute hepatitis caused by rat HEV have been reported in Hong Kong, Canada (infection acquired in Central Africa), and Spain (6-8).Those reports raise concerns regarding the potential risk for rat HEV transmission to humans and hepatitis E as an emerging infectious disease worldwide. The StudyWe conducted a study to investigate HEV infection in Norway rats from southern Ontario, Canada, and identify associations between host factors, season, land use, and year of collection.We obtained rat carcasses through collaboration with pest control professionals working in southern Ontario.Our rat and sample collection methods have been previously described and evaluated as a source of samples for zoonotic pathogen surveillance (9).We studied 372 Norway rats (species determined by external morphology) from 161 unique geographic coordinates within southern Ontario during November 2018-June 2021 (Figure 1).During necropsy, we recorded rat demographic characteristic data (Table ) and collected liver samples aseptically.Most rats in our sample were sexually mature (65%), and there were more females (51.2%) than males (48.8%).We noted the body condition of rats to be poor (emaciated or underconditioned) in 69.1% and good (well conditioned or overconditioned) in 30.9%.We could not determine sex (3%), sexual maturity (3.2%), or body condition (2.4%) in a minority of rats because of poor carcass condition.We categorized rats by collectionRat Hepatitis E Virus in Norway Rats, Ontario, Canada, 2018-2021