Hepatitis E virus isolates of genotype 4 recovered from wild boars in the Iriomote Island, Okinawa

Prevalence and genotype/subtype distribution of hepatitis E virus (HEV) among wild boars in Japan: Identification of a genotype 5 HEV strain

To further investigate the prevalence of hepatitis E virus (HEV) infection and characterize HEV genomes among Japanese wild boars (Sus scrofa leucomystax), 1880 boars captured in 17 prefectures in Japan from 2013 to 2019 were studied. Overall, anti-HEV IgG was detected in 8.9 % and HEV RNA was detected in 3.9 % of boars, which was comparable with our previous studies during 2003-2013 (10.3 % and 3.5 %, respectively). Among 74 boar HEV strains obtained from infected boars in the present study, 50 (68 %) were classified into genotype 3 (3a and 3b), 23 (31 %) were classified into genotype 4 (4i), and the remaining strain (wbJGF_19-1) was classified into genotype 5. The wbGF_19-1 strain shared 92.7 % identity over the entire genome with the prototype genotype 5 strain (JBOAR135-Shiz09). The identification of the second genotype 5 HEV strain in a place that is located only 100 km from the site at which JBOAR135-Shiz09 was identified, suggests that genotype 5 HEV circulates within a relatively close range in Japan. Genetically similar HEV strains forming a clade were identified from wild boars living in each area during the observation period of 11-13 years, although the nucleotide sequence changed gradually, accounting for up to 3.4-3.6 % within the 412-nucleotide ORF2 sequence. Eight groups of boars with a cluster of HEV infections were observed, consisting of two, three or four infected offspring, presumably born to the same mother or offspring with their mother. These results suggest that wild boars continue to be important reservoirs for HEV infection in humans in Japan.

High genomic similarity between European type hepatitis E virus subgenotype 3e strains isolated from an acute hepatitis patient and a wild boar in Mie, Japan

A 67-year-old male living in Tsu city, Mie prefecture, Japan was referred to our hospital for further examination of acute liver injury and was diagnosed as having clinical hepatitis E virus (HEV) infection in January 2010. The HEV strain (HE-JA11-1701) isolated from the patient belonged to genotype 3 and European-type subgenotype 3e. It was presumed that the patient had been infected from a wild boar (Sus scrofa leucomystax) because he consumed meat/viscera from a wild boar that he had captured himself as a hunter approximately 2 months before disease onset. A specimen of the boar meat/viscera that the patient had ingested was not available. However, the HE-JA11-1701 strain was 99.8% identical within the 412-nucleotide sequence of the open reading frame 2 region to a HEV strain (JBOAR012-Mie08) that had been recovered from a wild boar captured near the patient's hunting area in 2008. A phylogenetic analysis confirmed that the two HEV strains had a close genetic relationship and were segregated into subgenotype 3e, supported by a high bootstrap value of 99%. Of note, the HE-JA11-1701 and JBOAR012-Mie08 strains were remotely related to the 3e strains reported in Japan and European countries, with a nucleotide difference of 7.9-13.9%, reinforcing the uniqueness of the 3e strains obtained in the present study. These results strongly support our speculation that the patient developed acute hepatitis E via consumption of HEV-infected boar meat/viscera. Genetic analyses of HEV strains are useful for tracing infectious sources in sporadic cases of acute hepatitis E.

Features of hepatitis E virus infection in humans and animals in Japan

In Japan, hepatitis E had long been considered to be a rare liver disease which can be accidentally imported from endemic countries in Asia and Africa, where the sanitation conditions are suboptimal. However, since the identification of the first autochthonous hepatitis E case and hepatitis E viremic domestic pigs in Japan in 2001, our understanding of hepatitis E virus (HEV) infection in this country has been changing markedly. This has largely been due to the development of serological and gene-based diagnostic assays, the accumulation of molecular epidemiological findings on HEV infection in humans and animals (as potential reservoirs for HEV in humans) and the recognition of the importance of zoonotic food-borne and other routes of transmission of HEV, including blood-borne transmission. Although it is now evident that autochthonous hepatitis E in Japan is far more common than was previously thought, clinical and subclinical HEV infections indigenous to Japan remain underdiagnosed and their prevalence is still underestimated due to the presence of unknown transmission routes and a low awareness of the infection status by many physicians in Japan. This review focuses on the features of HEV infection in humans and animals, as definitive or potential reservoirs for HEV, in Japan, and updates the current knowledge on the routes of transmission, including zoonotic routes, which are important for the maintenance and spread of HEV in Japan.

A serological survey of selected pathogens in wild boar (Sus scrofa) in northern Turkey

During the hunting season in March 2012, a total of 93 blood samples were collected from wild boars (Sus scrofa) shot in the area of northern Turkey (Samsun and Gumushane provinces). These blood samples were examined by enzyme immunoassay (ELISA) for the presence of antibodies to classical swine fever virus (CSFV), Aujeszky's disease virus (ADV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine respiratory coronavirus (PRCV), swine influenza virus (SIV), porcine parvovirus (PPV), swine vesicular disease virus (SVDV), hepatitis E virus (HEV), African swine fever virus (ASFV), porcine rotavirus (PRV), transmissible gastroenteritis virus (TGEV) and bovine viral diarrhoea virus (BVDV). Out of 93 serum samples examined, 65 (69.9 %) were positive for PRV, 22 (23.7 %) were positive for ADV, 5 (5.4 %) were positive for BVDV, 4 (4.3 %) were positive for PPV and 2 (2.2 %) were positive for PRRSV. All sera were negative for ASFV, SVDV, HEV, SIV, PRCV, TGEV and CSFV. The results, recorded for the first time in Turkey, supported the hypothesis that wild boar act as a potential reservoir of selected viruses and thus have a role in the epidemiology of these diseases.

A nationwide survey of hepatitis E virus (HEV) infection in wild boars in Japan: identification of boar HEV strains of genotypes 3 and 4 and unrecognized genotypes

To investigate the nationwide prevalence of hepatitis E virus (HEV) infection and to characterize HEV genomes among Japanese wild boars (Sus scrofa leucomystax), 578 boars captured in 25 prefectures from 2003 to 2010 were studied. Anti-HEV IgG was detected in 8.1%, and HEV RNA in 3.3% of boars. Among the 19 boar HEV isolates obtained from infected boars, 14 isolates (74%) were classified as genotype 3, 4 isolates (21%) as genotype 4, and the remaining isolate (wbJOY_06) was distantly related to all known HEV isolates of genotypes 1-4, differing by 18.4-25.0% and 18.0-24.3% within the 412-nucleotide sequence of ORF1 and ORF2, respectively. A genotype 4 boar HEV isolate (wbJGF_08-1) obtained herein shared 98.6% identity over the entire genome with a human HEV isolate obtained from a patient who developed acute hepatitis after consuming undercooked wild boar meat, suggesting that wild boars are also reservoirs for genotype 4 HEV in humans.

A review of viral diseases of the European wild boar: effects of population dynamics and reservoir rôle

There has been a worldwide increase in the number and geographical spread of wild boar populations in recent decades leading to an increase in both the circulation of disease agents and greater contact with domestic animals and humans. Diseases affect the population dynamics of wildlife but the effects of most viral diseases on the European wild boar are largely unknown. Many viral diseases present in domestic pig populations are also present in wild boars where they can provide a disease reservoir, as is clearly the case with classical swine fever, but little is known about other viral diseases such as porcine circovirus diseases or hepatitis E. This review considers the current scientific knowledge of the effects of viral diseases on wild boar populations and their rôle as potential disease reservoirs. The focus is on those viral diseases of domestic swine and wild boars that are included as notifiable by the Office International des Epizooties (OIE).