Characterization of hepatitis E virus natural infection in farmed rabbits

Detection of Hepatitis E Virus in Rabbits and Rabbit Meat from Slaughterhouses in Hebei Province of China

Background: Hepatitis E virus (HEV) is a zoonotic pathogen. HEV has been found to be widely prevalent in rabbits. Its isolates are classified into HEV-3, rabbit subgenotype (HEV-3ra). The routes of human infection with HEV-3ra remain unclear; however, foodborne transmission is possible when asymptomatically infected animals enter the food chain. The prevalence of HEV infection in slaughtered rabbits and the presence of HEV in rabbit meat were evaluated in this study. Materials and Methods: In three slaughterhouses in Hebei province, China, samples of rabbit blood were collected during the slaughter process, and muscle, liver, and cavity juice were collected from the rabbit carcasses. Anti-HEV antibody in serum samples was detected using enzyme-linked immunosorbent assay. HEV RNA was tested in all samples by reverse transcription nested PCR (RT-nested PCR). The final amplicons of RT-nested PCR were sequenced and phylogenetically analyzed. Results: Of the 459 serum samples, 50 [10.9%, 95% confidence interval (CI): 8.1-13.7] were positive for anti-HEV antibody, and 17 (3.7%, 95% CI: 2.0-5.4) were positive for HEV RNA. HEV RNA was detected in 7 of 60 liver samples (11.7%, 95% CI: 3.3-20) and 2 cavity juice samples from semi-eviscerated carcasses, but was not detected in any muscle sample from either the eviscerated or semi-eviscerated carcasses. All the detected HEV strains belonged to HEV-3ra and related most closely with the rabbit HEV sequence previously reported in China. Conclusion: A portion of rabbits were in the viremia period of HEV infection at the slaughter age, resulting in the possibility of HEV carriage by rabbit carcass, particularly semi-eviscerated carcass containing liver. These findings suggest a potential risk of HEV transmission from raw rabbit products entering the food chain, whereas the presence of HEV appeared to be lower in the eviscerated carcass than in the semi-eviscerated carcass.

Hepatitis E Virus in Livestock-Update on Its Epidemiology and Risk of Infection to Humans

Hepatitis E virus (HEV) is a public health problem worldwide and an important food pathogen known for its zoonotic potential. Increasing numbers of infection cases with human HEV are caused by the zoonotic transmission of genotypes 3 and 4, mainly by consuming contaminated, undercooked or raw porcine meat. Pigs are the main reservoir of HEV. However, it should be noted that other animal species, such as cattle, sheep, goats, and rabbits, may also be a source of infection for humans. Due to the detection of HEV RNA in the milk and tissues of cattle, the consumption of infected uncooked milk and meat or offal from these species also poses a potential risk of zoonotic HEV infections. Poultry infected by avian HEV may also develop symptomatic disease, although avian HEV is not considered a zoonotic pathogen. HEV infection has a worldwide distribution with different prevalence rates depending on the affected animal species, sampling region, or breeding system.

Oral Zinc Supplementation in Chronically HEV-Infected Patients Not Responding to Ribavirin Monotherapy

Background: Chronic hepatitis E virus (HEV) infection may progress to end-stage liver disease in immunosuppressed individuals. Ribavirin therapy is efficient in most chronic HEV patients, but 10% remain without a sustained virological response (SVR). Objectives: We aimed to study whether zinc supplementation could represent a therapeutic approach in these patients. Methods: Antiviral properties of zinc salts were studied in vitro (subgenomic-replicon system), in vivo (rabbit model), and retrospectively in patients with chronic hepatitis E who did not achieve SVR under ribavirin monotherapy. Results: Zinc inhibited HEV genotype-3 replication in vitro. In a model of acute HEV infection in immunocompetent rabbits, zinc + ribavirin did not improve viral clearance compared to ribavirin monotherapy. In chronically HEV-infected patients not responding to ribavirin (n = 12), viral clearance was observed in 4/12 (33%) patients receiving additional zinc supplementation. Conclusions: Oral zinc, an inexpensive, harmless dietary supplement, could potentially represent a rescue treatment option for a few patients with chronic hepatitis E without SVR under ribavirin monotherapy. Further studies are needed to elucidate the role of zinc in HEV further.

Absence of Hepatitis E Virus (HEV) in Italian Lagomorph Species Sampled between 2019 and 2021

The zoonotic hepatitis E virus genotype 3 (HEV-3) causes most autochthonous human hepatitis E cases in Europe, which are due to the consumption of raw or undercooked food products of animal origin. Pigs and wild boars are considered the main reservoirs of this genotype, while rabbits are the reservoir of a distinct phylogenetic group named HEV-3ra, which is classified within the HEV-3 genotype but in a separate clade. Evidence for the zoonotic potential of HEV-3ra was suggested by its detection in immunocompromised patients in several European countries. HEV-3ra infection was found in farmed and feral rabbit populations worldwide and its circulation was reported in a few European countries, including Italy. Furthermore, Italy is one of the major rabbit meat producers and consumers across Europe, but only a few studies investigated the presence of HEV in this reservoir. The aim of this study was to assess the presence of HEV in 328 Italian hares and 59 farmed rabbits collected in 3 Italian macro-areas (North, North-Central, and South-Central), between 2019 and 2021. For this purpose, liver samples were used to detect HEV RNA using broad-range real-time RT-PCR and nested RT-PCR. Using 28 liver transudates from hares, the ELISA test for anti-HEV IgG detection was also performed. Neither HEV RNA nor anti-HEV antibodies were detected. Further studies will be conducted to assess the HEV presence in Italian lagomorphs to establish the role of this host and the possible risk of transmission for workers with occupational exposure, to pet owners and via food.

A small animal model of chronic hepatitis E infection using immunocompromised rats

Background & Aims

HEV variants such as swine genotypes within Paslahepevirus species balayani (HEV-A) and rat HEV (Rocahepevirus ratti; HEV-C1) cause chronic hepatitis E in immunocompromised individuals. There are few reliable and accessible small animal models that accurately reflect chronic HEV infection. We aimed to develop an immunocompromised rat model of chronic hepatitis E infection.

Methods

In this animal model infection study, rats were immunosuppressed with a drug combination (prednisolone, tacrolimus, and mycophenolate mofetil) commonly taken by transplant recipients. Rats were challenged with human- and rat-derived HEV-C1 strains or a human-derived HEV-A strain. Viral load, liver function, liver histology, humoural, and cellular immune responses were monitored.

Results

A high-dose (HD) immunosuppressive regimen consistently prolonged human- and rat-derived HEV-C1 infection in rats (up to 12 weeks post infection) compared with transient infections in low-dose (LD) immunosuppressant-treated and immunocompetent (IC) rats. Mean HEV-C1 viral loads in stool, serum, and liver tissue were higher in HD regimen-treated rats than in LD or IC rats (p <0.05). Alanine aminotransferase elevation was observed in chronically infected rats, which was consistent with histological hepatitis and HEV-C1 antigen expression in liver tissue. None (0/6) of the HD regimen-treated, 5/6 LD regimen-treated, and 6/6 IC rats developed antibodies to HEV-C1 in species-specific immunoblots. Reversal of immunosuppression was associated with clearance of viraemia and restoration of HEV-C1-specific humoural and cellular immune responses in HD regimen-treated rats, mimicking patterns in treated patients with chronic hepatitis E. Viral load suppression was observed with i.p. ribavirin treatment. HD regimen-treated rats remained unsusceptible to HEV-A infection.

Conclusions

We developed a scalable immunosuppressed rat model of chronic hepatitis E that closely mimics this infection phenotype in transplant recipients.

Lay summary

Convenient small animal models are required for the study of chronic hepatitis E in humans. We developed an animal model of chronic hepatitis E by suppressing immune responses of rats with drugs commonly taken by humans as organ transplant rejection prophylaxis. This model closely mimicked features of chronic hepatitis E in humans.

•

Chronic HEV infection is challenging to model with small animals.

•

Rats can be immunocompromised by transplant rejection drugs taken by patients.

•

This model supports chronic rat HEV infection robustly and consistently.

•

Immunosuppression in this model is scalable, reversible, and responsive to ribavirin.

The Foodborne Transmission of Hepatitis E Virus to Humans

Globally, Hepatitis E virus (HEV) causes over 20 million cases worldwide. HEV is an emerging and endemic pathogen within economically developed countries, chiefly resulting from infections with genotype 3 (G3) HEV. G3 HEV is known to be a zoonotic pathogen, with a broad host range. The primary source of HEV within more economically developed countries is considered to be pigs, and consumption of pork products is a significant risk factor and known transmission route for the virus to humans. However, other foods have also been implicated in the transmission of HEV to humans. This review consolidates the information available regarding transmission of HEV and looks to identify gaps where further research is required to better understand how HEV is transmitted to humans through food.

First description of hepatitis E virus in Australian rabbits

We report the first detection of hepatitis E virus in rabbits in Australia. While conducting metatranscriptomic sequencing of liver samples collected from domestic rabbits that had died, we detected hepatitis E virus in three samples. Two viral genome sequences were obtained, which shared 96% nucleotide identity and clustered with hepatitis E strains isolated from rabbits and humans in Europe. This raises a potential public health risk in Australia, as the abundance of wild rabbits and the increasing popularity of domestic rabbits as pets represent a substantial human/rabbit interface to allow for potential zoonotic infections to occur.