Prevalence of hepatitis E virus in domestic animals in the Chinese mainland: a systematic review and meta-analysis

BACKGROUND

China, especially the Chinese mainland, is a highly endemic area of hepatitis E, and its incidence rate has been increasing in recent years. Hepatitis E virus (HEV) is the causative agent of hepatitis E, with a variety of domestic animals as potential hosts. The shift in the main epidemic strain and the increasing trend of zoonotic HEV infection in the Chinese mainland need urgent attention. This systematic review aimed to provide a summary of HEV detection and its characteristics in domestic animals in the Chinese mainland.

METHODS

A total of 1,019 literatures published in Chinese and English before 2024.1.15 were retrieved from four databases including Pubmed, ScienceDirect, Wan Fang and CNKI. Eventually, 73 eligible studies were included in this review, involving HEV detection data of 64,813 samples collecting from 13 kinds of common domestic animals, locating in 28 provinces and municipalities.

RESULTS

HEV antibodies and RNA were detected among 12 and 7 kinds of domestic animals respectively, with the pooled prevalence of 37.94% (95% CI:32.28-43.77) and 7.62% (95% CI: 5.56-9.96) respectively. The prevelance of HEV for swine samples was higher than other species. In addition, the prevalence of HEV among Tibetan swine, cattle and goats were also at a relatively high level. Further subgroup analysis focusing on comprehensive data from swine was conducted. The results showed, the seroprevalence of HEV antibodies gradually decreased over the time of sampling. HEV RNA was detected in various samples, including bile, feces, liver, and serum. The detection rate for fecal samples was the highest, which was 16.60% (95% CI: 12.17-21.55). Further genotyping of HEV RNA was classified. The results warn us about the circulation of genotype 3 HEV in the eastern region of the Chinese mainland.

CONCLUSION

The results collected from the included studies provided valuable data on HEV prevalence across various species, and the characteristics, trends, and potential influencing factors were fully discussed. This review provides public health professionals, policymakers, and researchers with comprehensive and up-to-date research data on zoonotic HEV.

Hepatitis E as a Zoonosis

Hepatitis E viruses in the family of Hepeviridae have been classified into 2 genus, 5 species, and 13 genotypes, involving different animal hosts of different habitats. Among all these genotypes, four (genotypes 3, 4, 7, and C1) of them are confirmed zoonotic causing sporadic human diseases, two (genotypes 5 and 8) were likely zoonotic showing experimental animal infections, and the other seven were not zoonotic or unconfirmed. These zoonotic HEV carrying hosts include pig, boar, deer, rabbit, camel, and rat. Taxonomically, all the zoonotic HEVs belong to the genus Orthohepevirus, which include genotypes 3, 4, 5, 7, 8 HEV in the species A and genotype C1 HEV in the species C. In the chapter, information of zoonotic HEV such as swine HEV (genotype 3 and 4), wild boar HEV (genotypes 3-6), rabbit HEV (genotype 3), camel HEV (genotype 7 and 8), and rat HEV (HEV-C1) was provided in detail. At the same time, their prevalence characteristics, transmission route, phylogenetic relationship, and detection technology were discussed. Other animal hosts of HEVs were introduced briefly in the chapter. All these information help peer researchers have basic understanding of zoonotic HEV and adopt reasonable strategy of surveillance and prevention.

Genomic characteristics and recombination patterns of swine hepatitis E virus in China

Zoonotic hepatitis E, mainly caused by swine hepatitis E virus (sHEV), is endemic in China, causing great economic disruption and public health threats. Although recombination is critical for the evolution of viruses, there is a limited assessment of its occurrence among sHEVs. Herein, we analyzed all available sHEV full-length genomes isolated in China during the past two decades (40 isolates) compared to 72 other sHEV strains isolated in different countries and determined that sHEV genotype 4 (sHEV4) dominates China. Eight potential natural recombination events were identified, four of which occurred in China and were mainly between sHEV4 strains, indicating the distinct character of China sHEV. One intergenotype recombination event was found in China, alarming the emergence of a new sHEV lineage that could become a critical threat to human health. This article is protected by copyright. All rights reserved.

Prevalence of hepatitis E virus among swine in China from 2010 to 2019: A systematic review and meta-analysis

Hepatitis E virus (HEV) is a zoonotic pathogen that has spread worldwide. The HEV reservoir associated with livestock hepatitis E poses a huge threat to public health. Awareness of the prevalence and spatial distribution of livestock hepatitis E is valuable to prevent and control diseases caused by HEV, especially human hepatitis E infection. Currently, swine, including pigs (Sus scrofa), are recognized as the major reservoir of HEV. Therefore, we conducted a systematic review and meta-analysis to evaluate the pooled prevalence of HEV among swine in China. A total of 71 published papers on HEV infection in swine in China (including data from 49,523 animals) from January 1, 2010 to December 31, 2019 met the standard after searching five databases including the Technology Periodical Database, the Wan Fang Database, the China National Knowledge Infrastructure, PubMed, and ScienceDirect. A random effects model was used to calculate the pooled prevalence of HEV in swine. The results showed that the seroprevalence was 48.0% (95% confidence interval (CI) 39.6-56.9) and the prevalence of HEV RNA was 14.4% (95% CI 10.7-18.5). The estimated overall prevalence was 34.1% (95% CI 27.2-41.4). Central China (68.0%, 95% CI 42.2-89.1) had a significantly higher prevalence than other regions. In the publication year subgroup, the prevalence in 2016 or later (27.2%, 95% CI 19.3-36.0) was significantly lower than that in 2011 or earlier (49.0%, 95% CI 36.2-61.8). The prevalence of IgG (42.9%, 95% CI 31.7-54.6) was significantly higher than that of IgM (4.9%, 95% CI 1.6-9.7). Suckling piglets (15.6%, 95% CI 6.6-27.1) had a lower prevalence compared with that in other age groups. In all sample types, body fluids showed the highest prevalence (50.5%, 95% CI 41.7-59.3). Moreover, the pooled prevalence of HEV in boars was higher than that in sows (35.4% > 17.3%). The analysis suggested that HEV infection is common among swine in China. Further strengthening HEV testing in boars, controlling environmental pollution, and reducing the mixed feeding of different stages could contribute to reducing HEV infection in pigs in China and the risk of porcine HEV infection in humans.

Hepatitis E as a Zoonosis

Hepatitis E (HE) virus infection is not limited to spread from human to human but also occurs between animals and more importantly as zoonotic spread from animals to humans. Genotyping of strains from hepatitis E virus-infected patients has revealed that these infections are not all caused by genotypes 1 or 2 but often by genotypes 3 or 4. Therefore, it is important to understand the striking difference between the spread of genotypes 1 and 2 in countries with poor sanitary standards and the spread of genotypes 3 and 4 in countries with good sanitary standards. The number of animal species known to be infected with HEV is expanding rapidly. The finding of HEV in new host species always raises the question regarding the zoonotic potential of these newfound strains. However, as new strains are found, the complexity increases.Certain genotypes are known to have the ability of zoonotic spread from certain animal species and these animals may even constitute an infection reservoir. Some animal species may contribute to zoonotic infections albeit on a smaller scale, while others are believed to be of minor or no importance at all. This chapter reviews possible sources of zoonotic hepatitis E virus infection.

Construction of an infectious cDNA clone of a swine genotype 3 HEV strain isolated in Shanghai, China

OBJECTIVES

Infectious cDNA clones are important tools for studying molecular mechanisms in RNA viruses. The aim of this study was to construct an infectious cDNA clone for SAAS-JDY5, which is a genotype 3 HEV strain of swine origin.

METHODS

Construction employed overlapping PCR and restriction analysis to ligate nine cDNA fragments into a full-length cDNA clone containing 14 mutations compared to the consensus HEV genome sequence. Megaprimer PCR-directed mutagenesis restored nine non-silent mutations back to the consensus sequence while the other five silent mutations were maintained as genetic markers.

RESULTS

HEV proteins were identified by an immunofluorescence assay in Huh7 cells infected with capped RNA transcripts of the full-length cDNA clone, while HEV viremia, fecal HEV RNA and seroconversion were recorded in inoculated Sprague-Dawley rats.

CONCLUSIONS

Our data confirmed the successful construction of an infectious cDNA clone of swine HEV strain pGEM4z-SAAS-JDY5, and support the use of rats as an HEV infectious model.