Subclinical avian hepatitis E virus infection in layer flocks in the United States

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.

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.

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.

Chicken Organic Anion-Transporting Polypeptide 1A2, a Novel Avian Hepatitis E Virus (HEV) ORF2-Interacting Protein, Is Involved in Avian HEV Infection

Avian hepatitis E virus (HEV) is the main causative agent of big liver and spleen disease in chickens. Due to the absence of a highly effective cell culture system, there are few reports about the interaction between avian HEV and host cells. In this study, organic anion-transporting polypeptide 1A2 (OATP1A2) from chicken liver cells was identified to interact with ap237, a truncated avian HEV capsid protein spanning amino acids 313 to 549, by a glutathione S-transferase (GST) pulldown assay. GST pulldown and indirect enzyme-linked immunosorbent assays (ELISAs) further confirmed that the extracellular domain of OATP1A2 directly binds with ap237. The expression levels of OATP1A2 in host cells are positively correlated with the amounts of ap237 attachment and virus infection. The distribution of OATP1A2 in different tissues is consistent with avian HEV infection in vivo Finally, when the functions of OATP1A2 in cells are inhibited by its substrates or an inhibitor or blocked by ap237 or anti-OATP1A2 sera, attachment to and infection of host cells by avian HEV are significantly reduced. Collectively, these results displayed for the first time that OATP1A2 interacts with the avian HEV capsid protein and can influence viral infection in host cells. The present study provides new insight to understand the process of avian HEV infection of host cells.IMPORTANCE The process of viral infection is centered around the interaction between the virus and host cells. Due to the lack of a highly effective cell culture system in vitro, there is little understanding about the interaction between avian HEV and its host cells. In this study, a total of seven host proteins were screened in chicken liver cells by a truncated avian HEV capsid protein (ap237) in which the host protein OATP1A2 interacted with ap237. Overexpression of OATP1A2 in the cells can promote ap237 adsorption as well as avian HEV adsorption and infection of the cells. When the function of OATP1A2 in cells was inhibited by substrates or inhibitors, attachment and infection by avian HEV significantly decreased. The distribution of OATP1A2 in different chicken tissues corresponded with that in tissues during avian HEV infection. This is the first finding that OATP1A2 is involved in viral infection of host cells.

Fiber-based fluorescent microsphere immunoassay (FMIA) as a novel multiplex serodiagnostic tool for simultaneous detection and differentiation of all clinically relevant fowl adenovirus (FAdV) serotypes

The recent emergence of fowl aviadenovirus (FAdV) induced disease outbreaks in chicken flocks worldwide, with distinct aetiologies confined to particular FAdV species and serotypes, is increasingly urging the need for specific and mass-applicable antibody screening systems. Despite this exigency, there are to date no available serological procedures which satisfactorily combine the criteria for sensitive detection of antibodies against FAdVs, diagnostic reliability in face of cross-reactions and requirements for a rapid and large-scale application. In order to address this gap, a multiplexed fluorescent microsphere immunoassay (FMIA) based on recombinant FAdV fiber proteins from six different serotypes FAdV-1, -2, -4, -8a, -8b and -11 was developed, which enabled simultaneous detection of antibodies against all clinically relevant serotypes in a single reaction within a high throughput setting. Based on a panel of >300 monospecific antisera raised against each of the 12 FAdV serotypes, 100% serotype-specificity was demonstrated for FAdV-1 (FAdV-A) and FAdV-4 (FAdV-C) fiber-based analytes. Analytes based on serotypes affiliated to FAdV-D and FAdV-E exhibited moderately lower specificities of 91.2-95.7%. This was attributed almost exclusively to mutual recognition between FAdV-2 and -11 field strains and to a much lesser extent to reference strains, supporting earlier proposals to merge them into a single serotype. Similarly, extensive cross-reactions between FAdV-8a and -8b were noted. Altogether intraspecies cross-reactions can be attributed to viruses with a close etiological intersection. Antisera against other important avian viruses remained negative by the FMIA, further validating its specificity. Compared to the virus-neutralization (VN) test, FMIA and individual fiber-based enzyme-linked immunosorbent assays (ELISAs) were equally sensitive in the detection of sera against FAdV-2 and -11, as well as FAdV-8a and -8b field strains, while they were even superior to VN test in detection of FAdV-1 and FAdV-4 responses, likely attributed to a relative abundance of fiber antibodies early upon infection. Moreover, application of the FMIA on field samples comprising a diversified response against all 12 FAdV serotypes further consolidated its specificity and agreement with VN test.

Zoonotic Hepatitis E Virus: An Ignored Risk for Public Health

Hepatitis E virus (HEV) is a quasi-enveloped, single-stranded positive-sense RNA virus. HEV belongs to the family Hepeviridae, a family comprised of highly diverse viruses originating from various species. Since confirmation of HEV's zoonosis, HEV-induced hepatitis has been a public health concern both for developing and developed countries. Meanwhile, the demonstration of a broad host range for zoonotic HEV suggests the existence of a variety of transmission routes that could lead to human infection. Moreover, anti-HEV antibody serosurveillance worldwide demonstrates a higher than expected HEV prevalence rate that conflicts with the rarity and sporadic nature of reported acute hepatitis E cases. In recent years, chronic HEV infection, HEV-related acute hepatic failure, and extrahepatic manifestations caused by HEV infection have been frequently reported. These observations suggest a significant underestimation of the number and complexity of transmission routes previously predicted to cause HEV-related disease, with special emphasis on zoonotic HEV as a public health concern. Significant research has revealed details regarding the virology and infectivity of zoonotic HEV in both humans and animals. In this review, the discovery of HEV zoonosis, recent progress in our understanding of the zoonotic HEV host range, and classification of diverse HEV or HEV-like isolates from various hosts are reviewed in a historic context. Ultimately, this review focuses on current understanding of viral pathogenesis and cross-species transmission of zoonotic HEV. Moreover, host factors and viral determinants influencing HEV host tropism are discussed to provide new insights into HEV transmission and prevalence mechanisms.

Effect of housing arrangement on fecal-oral transmission of avian hepatitis E virus in chicken flocks

BACKGROUND

Avian hepatitis E virus (HEV) infection is common in chicken flocks in China, as currently no measures exist to prevent the spread of the disease. In this study, we analyzed the effect of caged versus cage-free housing arrangements on avian HEV transmission. First, 127 serum and 110 clinical fecal samples were collected from 4 chicken flocks including the two arrangements in Shaanxi Province, China and tested for HEV antibodies and/or virus. Concurrently, 36 specific-pathogen-free chickens were divided equally into four experimental living arrangement groups, designated cage-free (Inoculated), caged (Inoculated), cage-free (Negative) and caged (Negative) groups. In caged groups, three cages contained 3 chickens each. Three chickens each from cage-free (Inoculated) and caged (Inoculated) groups (one chicken of each cage) were inoculated by cutaneous ulnar vein with the same dose of avian HEV, respectively. The cage-free (Negative) and caged (Negative) groups served as negative control. Serum and fecal samples were collected at 1 to 7 weeks post-inoculation (wpi) and liver lesions were scored at 7 wpi.

RESULTS

The results of serology showed that the avian HEV infection rate (54.10%) of the cage-free chickens was significantly higher than the one (12.12%) for caged chickens (P < 0.05). Also, the rate of detection of avian HEV RNA in the clinical fecal samples was significantly higher in the cage-free (22.80%, 13/57) than caged birds (5.66%, 3/53). Moreover, under experimental conditions, the infected number of uninoculated cage-free chickens (6) was significantly higher than the one for the uninoculated caged birds (2), as evidenced by seroconversion, fecal virus shedding, viremia and gross and microscopic liver lesions.

CONCLUSIONS

These results suggest that reduction of contact with feces as seen in the caged arrangement of housing chickens can reduce avian HEV transmission. This study provides insights for prevention and control of avian HEV infection in chicken flocks.

Detection of rat hepatitis E virus in wild Norway rats (Rattus norvegicus) and Black rats (Rattus rattus) from 11 European countries

Rat hepatitis E virus (HEV) is genetically only distantly related to hepeviruses found in other mammalian reservoirs and in humans. It was initially detected in Norway rats (Rattus norvegicus) from Germany, and subsequently in rats from Vietnam, the USA, Indonesia, China, Denmark and France. Here, we report on a molecular survey of Norway rats and Black rats (Rattus rattus) from 12 European countries for ratHEV and human pathogenic hepeviruses. RatHEV-specific real-time and conventional RT-PCR investigations revealed the presence of ratHEV in 63 of 508 (12.4%) rats at the majority of sites in 11 of 12 countries. In contrast, a real-time RT-PCR specific for human pathogenic HEV genotypes 1-4 and a nested broad-spectrum (NBS) RT-PCR with subsequent sequence determination did not detect any infections with these genotypes. Only in a single Norway rat from Belgium a rabbit HEV-like genotype 3 sequence was detected. Phylogenetic analysis indicated a clustering of all other novel Norway and Black rat-derived sequences with ratHEV sequences from Europe, the USA and a Black rat-derived sequence from Indonesia within the proposed ratHEV genotype 1. No difference in infection status was detected related to age, sex, rat species or density of human settlements and zoological gardens. In conclusion, our investigation shows a broad geographical distribution of ratHEV in Norway and Black rats from Europe and its presence in all settlement types investigated.

Public health risks associated with hepatitis E virus (HEV) as a food-borne pathogen

Hepatitis E virus (HEV) is an important infection in humans in EU/EEA countries, and over the last 10 years more than 21,000 acute clinical cases with 28 fatalities have been notified with an overall 10-fold increase in reported HEV cases; the majority (80%) of cases were reported from France, Germany and the UK. However, as infection in humans is not notifiable in all Member States, and surveillance differs between countries, the number of reported cases is not comparable and the true number of cases would probably be higher. Food-borne transmission of HEV appears to be a major route in Europe; pigs and wild boars are the main source of HEV. Outbreaks and sporadic cases have been identified in immune-competent persons as well as in recognised risk groups such as those with pre-existing liver damage, immunosuppressive illness or receiving immunosuppressive treatments. The opinion reviews current methods for the detection, identification, characterisation and tracing of HEV in food-producing animals and foods, reviews literature on HEV reservoirs and food-borne pathways, examines information on the epidemiology of HEV and its occurrence and persistence in foods, and investigates possible control measures along the food chain. Presently, the only efficient control option for HEV infection from consumption of meat, liver and products derived from animal reservoirs is sufficient heat treatment. The development of validated quantitative and qualitative detection methods, including infectivity assays and consensus molecular typing protocols, is required for the development of quantitative microbial risk assessments and efficient control measures. More research on the epidemiology and control of HEV in pig herds is required in order to minimise the proportion of pigs that remain viraemic or carry high levels of virus in intestinal contents at the time of slaughter. Consumption of raw pig, wild boar and deer meat products should be avoided.