Complete genome analysis of avian hepatitis E virus from chicken with hepatic rupture hemorrhage syndrome

Pathogenicity of two different genotypes avian hepatitis E strains in laying hens and silkie fowl

To determine the pathogenicity of two different genotypes of avian hepatitis E strains in two species of birds, a total of thirty healthy 12-week-old birds were used. After inoculation, fecal virus shedding, viremia, seroconversion, serum alanine aminotransferase (ALT) increases and liver lesions were evaluated. The results revealed that CHN-GS-aHEV and CaHEV could both infect Hy-Line hens and silkie fowls, respectively. Compared to the original avian HEV strain, the cross-infected virus exhibited a delay of 2 weeks and 1 week in emerged seroconversion, viremia, fecal virus shedding, and increased ALT level, and also showed mild liver lesions. These findings suggested that CHN-GS-aHEV may have circulated in chickens. Overall, these two different genotypes of avian HEV showed some variant pathogenicity in different bird species. This study provides valuable data for further analysis of the epidemic conditions of two avian HEVs in Hy-Line hens and silkie fowls.

Hepatitis E virus causes apoptosis of ovarian cells in hens and resulting in a decrease in egg production

Previous studies have shown that avian hepatitis E virus (HEV) decreases egg production by 10-40% in laying hens, but have not fully elucidated the mechanism of there. In this study, we evaluated the replication of avian HEV in the ovaries of laying hens and the mechanism underlying the decrease in egg production. Forty 150-days-old commercial laying hens were randomly divided into 2 groups of 20 hens each. A total of 1 mL (104GE) of avian HEV stock was inoculated intravenously into each chicken in the experimental group, with 20 chickens in the other group serving as negative controls. Five chickens from each group were necropsied weekly for histopathological examination. The pathogenicity of avian HEV has been characterized by seroconversion, viremia, fecal virus shedding, ovarian lesions, and decreased egg production. Both positive and negative-strand avian HEV RNA, and ORF2 antigens can be detected in the ovaries, suggesting that avian HEV can replicate in the ovaries and serve as an important extrahepatic replication site. The ovaries of laying hens underwent apoptosis after avian HEV infection. These results indicate that avian HEV infection and replication in ovarian tissues cause structural damage to the cells, leading to decreased egg production.

Molecular diagnosis of patients with hepatitis A virus infection using amplicon-based nanopore sequencing

High-throughput sequencing is a robust tool used for identifying and tracking pathogen outbreaks. Whole-genome sequencing of hepatitis A virus (HAV) remains poor due to ultra-low viral loads, limitations of next-generation sequencing technology, and its high costs in clinical applications. This study evaluated multiplex polymerase chain reaction (PCR)-based nanopore sequencing to obtain whole-genome sequences of HAV. The HAV genomes were obtained directly from patient specimens for a rapid molecular diagnosis of viral genotypes. Serum and stool samples were collected from six patients with hepatitis A infection. Amplicon-based nanopore sequencing was performed from the clinical specimens to identify HAV genotypes by acquiring nearly complete-genome sequences. TaqMan-based quantitative PCR (qPCR) was conducted to detect and quantify multiple HAV genes. Singleplex-based nanopore sequencing demonstrated high genome coverage rates (90.4-99.5%) of HAV within 8 h, at viral RNA loads of 10 to 105 copies/μL. TaqMan qPCR showed multiplex quantification of HAV genes namely, VP0, VP3, and 3C. This study provides useful insights into rapid molecular diagnosis during hepatitis A outbreaks and may ultimately augment public health disease surveillance in the hospital and epidemiology field.

Virome Profiling of Chickens with Hepatomegaly Rupture Syndrome Reveals Coinfection of Multiple Viruses

Liver diseases seriously challenge the health of chickens raised on scaled farms and cause tremendous economic losses to farm owners. The causative agents for liver diseases are still elusive, even though various pathogens, such as the hepatitis E virus, have been reported. In the winter of 2021, a liver disease was observed on a chicken farm in Dalian, China, which increased chicken mortality by up to 18%. We conducted panvirome profiling of the livers, spleens, kidneys, and recta of 20 diseased chickens. The viromic results revealed coinfection of multiple viruses, including pathogenic ones, in these organs. The viruses were highly identical to those detected in other provinces, and the vaccine and field strains of avian encephalomyelitis virus (AEV) and chicken infectious anemia virus (CIAV) cocirculated on the farm. In particular, the liver showed higher abundance of AEV and multiple fowl adenoviruses than other organs. Furthermore, the liver also contracted avian leukemia virus and CIAV. Experimental animals with infected liver samples developed minor to medium lesions of the liver and showed a virus abundance profile for AEV across internal organs similar to that in the original samples. These results suggest that coinfection with multiple pathogenic viruses influences the occurrence and development of infectious liver disease. The results also highlight that strong farm management standards with strict biosafety measures are needed to minimize the risk of pathogenic virus introduction to the farm.

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.

A novel genotype of avian hepatitis E virus identified in chickens and common pheasants (Phasianus colchicus), extending its host range

In 2019, outbreaks of hepatitis-splenomegaly syndrome (HSS) were observed in six commercial layer chicken flocks, belonging to three different Polish farms, and characterized by increased mortality, hemorrhagic hepatitis with attached blood clots on the liver surface, and splenomegaly. Diseased flocks were initially investigated for the presence of avian hepatitis E virus (aHEV) - the etiological agent of HSS - by conventional reverse transcriptase polymerase chain reaction, which revealed aHEV sequences clustering separately from all known aHEV genotypes. Additionally, an aHEV genome was identified for the first time in common pheasants, from a flock in France, using Next Generation Sequencing. This genome clustered together with the Polish aHEVs here investigated. Complete genome aHEV sequences from the HSS outbreaks confirmed the divergent cluster, with a shared nucleotide sequence identity of 79.6-83.2% with other aHEVs, which we propose to comprise a novel aHEV genotype - genotype 7. Histology and immunohistochemistry investigations in the liver and spleen established an association between aHEV and the observed lesions in the affected birds, consolidating the knowledge on the pathogenesis of aHEV, which is still largely unknown. Thus, the present investigation extends the natural host range and genotypes of aHEV and strengthens knowledge on the pathogenesis of HSS.

Genotyping and Molecular Diagnosis of Hepatitis A Virus in Human Clinical Samples Using Multiplex PCR-Based Next-Generation Sequencing

Hepatitis A virus (HAV) is a serious threat to public health worldwide. We used multiplex polymerase chain reaction (PCR)-based next-generation sequencing (NGS) to derive information on viral genetic diversity and conduct precise phylogenetic analysis. Four HAV genome sequences were obtained using multiplex PCR-based NGS. HAV whole-genome sequence of one sample was obtained by conventional Sanger sequencing. The HAV strains demonstrated a geographic cluster with sub-genotype IA strains in the Republic of Korea. The phylogenetic pattern of HAV viral protein (VP) 3 region showed no phylogenetic conflict between the whole-genome and partial-genome sequences. The VP3 region in serum and stool samples showed sensitive detection of HAV with differences of quantification that did not exceed <10 copies/μL than the consensus VP4 region using quantitative PCR (qPCR). In conclusion, multiplex PCR-based NGS was implemented to define HAV genotypes using nearly whole-genome sequences obtained directly from hepatitis A patients. The VP3 region might be a potential candidate for tracking the genotypic origin of emerging HAV outbreaks. VP3-specific qPCR was developed for the molecular diagnosis of HAV infection. This study may be useful to predict for the disease management and subsequent development of hepatitis A infection at high risk of severe illness.

Identification of a Putative Novel Genotype of Avian Hepatitis E Virus from Apparently Healthy Chickens in Southwestern Nigeria

Avian hepatitis E virus (aHEV) is the major etiological agent of hepatitis-splenomegaly syndrome (HSS), big liver and spleen disease (BLSD), and hepatic rupture hemorrhage syndrome (HRHS) in chickens. Infections with aHEV cause a significant decrease in egg production and increased mortality in chickens worldwide. However, studies on the prevalence of aHEV in Nigeria are scarce. In this study, serum (n = 88) and fecal samples (n = 110) obtained from apparently healthy layer chickens from three states in southwestern Nigeria were analyzed by nested reverse transcription-polymerase chain reaction (nRT-PCR) targeting the helicase and capsid gene for the presence of aHEV. Avian HEV was detected in 12.5% (n = 11/88) of serum samples and 9.1% (n = 10/110) of fecal samples tested. Phylogenetic analysis showed that five of the twelve identified aHEV sequences belonged to genotype 2. The remaining seven sequences were only distantly related to other known aHEV isolates. After amplification of the near-complete ORF2 fragment (1618 bp) and part of the ORF1 (582 bp) of isolate YF40_aHEV_NG phylogenetic analysis revealed a nucleotide sequence identity between 79.0 and 82.6% and 80.1 and 83.5%, respectively, to other known aHEV strains, indicating that the Nigerian isolate YF40_aHEV_NG belongs to a novel aHEV genotype. This is the first report of co-circulation of aHEV genotypes in chickens in Nigeria.

Serological evidence of avian HEV antibodies in apparently healthy chickens in southwest Nigeria

Avian hepatitis E virus (aHEV) is associated with hepatitis-splenomegaly syndrome, big liver and spleen disease and hepatic rupture haemorrhage syndrome. However, the knowledge about aHEV in commercial layer chickens in Nigeria is scarce. In this study, 460 serum samples obtained from 36 apparently healthy commercial layer chicken flocks in three states (Ogun, Osun and Oyo States) of southwestern Nigeria were analysed by enzyme linked immunosorbent assay for the presence of anti-aHEV immunoglobulin Y (IgY) antibodies. In total, the overall seroprevalence of anti-aHEV antibodies was 14.6%. The serological analysis revealed that 75% of the flocks examined were positive for anti-aHEV IgY antibodies from chickens of various ages in all three states. The percentage of the seropositive chickens in the three states varied from flock to flock ranging from 60% to 88.8% and seropositive chickens were detected at any age (24-52 weeks of age) without significant differences between the age groups. This is the first report assessing the presence of aHEV antibodies in chickens from Nigeria. The detection of anti-aHEV antibodies in commercial layer chickens in this study emphasizes the importance of serosurveillance in disease monitoring due to the economic threat posed by aHEV as a result of decreased egg production and increased mortality in affected commercial layer chicken farms. However, further studies are essential to reveal the clinical implications and to assess the real burden of aHEV in Nigeria.

Research Note: A putative novel subtype of the avian hepatitis E virus of genotype 3, Jiangxi province, China

In recent years, the avian hepatitis E virus (HEV) has been widely spread in China, causing huge economic losses. Several studies have carried out detailed epidemiologic investigations of the avian HEV, but no data were from Jiangxi province. Since early April 2020, diseases similar to hepatic rupture hemorrhage syndrome caused by the avian HEV occurred in a Roman Brown layer farm in Jiangxi province, indicating this virus may also be epidemic there. To make this assumption clear, 20 liver samples were collected from the sick flock and then analyzed by detailed viral detection, which confirmed that the avian HEV should be responsible for the aforementioned disease (6 of 20). Then, the capsid gene of the virus was sequenced to show the molecular characteristics of the strain circulating in the aforementioned flock. Sequence comparison showed that it shared 80.7 to 94.7% identities with 12 published strains, while phylogenetic analysis confirmed that it belongs to a new subtype of genotype 3. Moreover, basing on a 242 bp fragment, the novel also shared high similarities to reference strains identified as genotypes before, revealing the genotype 3 maybe very popular in China and even can be divided into several subgroups. In conclusion, a novel avian HEV strain was identified in this study, which belongs to a new subtype of genotype 3. The analysis makes up for the molecular epidemiologic data of avian HEV and provides a basis for further understanding the spread of avian HEV in China.

Genetic diversity of avian hepatitis E virus in China, 2018-2019

Avian hepatitis E virus (HEV) is highly variable and has multiple genotypes. Previous studies showed that the current epidemic strain in China is genotype 5, but the relevant detection was only carried out in flocks with hepatic rupture haemorrhage syndrome, which does not mean that other genotypes do not exist. In this study, a broader analysis involving different chicken flocks was performed to understand the epidemic status of avian HEV in China. The results showed that the HEV-positive rate of all samples was 7.92% (78/985), and four different genotypes have been identified by analysing a truncate capsid gene fragment, while the homology between them is about 80%. Two of them are separately known as genotype 3 and genotype 5, while the other two are completely unidentified, indicating that there are multiple genotypes of avian HEV prevalent in China. At the same time, the distribution of these genotypes has no obvious geographical clustering pattern, only slightly different in commercial layers, broilers and some indigenous species. This study shows the genetic diversity of avian HEV in China and reminds us to pay more attention to its variation and evolution.

Identification and pathogenicity of a novel genotype avian hepatitis E virus from silkie fowl (gallus gallus)

Hepatitis E virus (HEV) is a public health concern because of its zoonotic potential; however, the host species spectrum and the genetic diversity of HEV in many birds are unknown. In the present study, a novel genotype avian HEV was isolated from a bird, silkie fowl, and designated CHN-GS-aHEV (GenBank No. MN562265). The genome of CHN-GS-aHEV was analyzed in comparison with other avian HEVs' and the pathogenicity in silkie fowl was characterized. The results show that the CHN-GS-aHEV shares about 81 % identity with known avian HEV in chickens, ORF3 shares the highest identity (85.1 %-88.0 %) at the nucleotide level, while ORF2 shares the highest identity (96.5 %-98.0 %) at the amino acid level, indicating that the CHN-GS-aHEV belongs to a new genotype avian HEV. The pathogenicity study showed that silkie fowl experimentally infected with the CHN-GS-aHEV demonstrated seroconversion, viremia, fecal virus shedding, liver lesions, and increased ALT level. Furthermore, ultrastructural changes in hepatocyte cells by transmission electron microscopy were characterized by the loss of mitochondrial cristae and swollen mitochondria and endoplasmic reticulum in the infected birds, suggesting that these two organelles may play a significant role in HEV replication. Overall, this study reports the complete genome characterization of a novel avian HEV and successful experimental infection in silkie fowl, and may be serving as a prominent indicator for additional avian HEV detection in other species.