Hepatitis E virus infection in Europe: regional situation regarding laboratory diagnosis and epidemiology

Hepatitis E: Still Waters Run Deep

Hepatitis E is an infectious inflammatory disease of the liver caused by the hepatitis E virus (HEV), a single-stranded RNA virus. Today, it is estimated that there are more than 20 million HEV infections every year, leading to 3.3 million symptomatic cases and more than 56,000 deaths. For a long time it was believed that HEV was a travel-associated disease, endemic in developing countries with poor hygienic standards and unsafe water supply. However, over the past years, publications have demonstrated that autochthonous HEV infections in industrialized countries are far more common than previously thought. Awareness for HEV amongst health care practitioners in industrialized countries is still limited. This relatively rare disease is of great importance, especially in immunocompromised patients where it can cause chronic liver disease. This article comprehensively reviews current literature to give an overview on clinically important topics. It will focus on epidemiological aspects, acute and chronic HEV infection as well as extra-hepatic manifestations, diagnostic approach and treatment options. Furthermore, the article is concluded with a brief outlook on perspectives and urgent problems to be addressed in the future.

Hepatitis E Virus in Domestic Pigs, Wild Boars, Pig Farm Workers, and Hunters in Estonia

While hepatitis E is a growing health concern in Europe, epidemiological data on hepatitis E virus (HEV) in Estonia are scarce. Along with imported HEV infections, autochthonous cases are reported from European countries. Both domestic and wild animals can be a source of human cases of this zoonosis. Here, we investigated the presence of anti-HEV antibodies and HEV RNA in domestic pigs and wild boars, as well as in pig farm workers and hunters in Estonia. Anti-HEV antibodies were detected in 234/380 (61.6%) of sera from domestic pigs and in all investigated herds, and in 81/471 (17.2%) of meat juice samples from wild boars. HEV RNA was detected by real-time PCR in 103/449 (22.9%) of fecal samples from younger domestic pigs and 13/81 (16.0%) of anti-HEV-positive wild boar samples. Analysis of sera from 67 pig farm workers and 144 hunters revealed the presence of HEV-specific IgG in 13.4 and 4.2% of the samples, respectively. No HEV RNA was detected in the human serum samples. Phylogenetic analyses of HEV sequences from domestic pigs and wild boars, based on a 245 bp fragment from the open reading frame 2 showed that all of them belonged to genotype 3. The present study demonstrates the presence of HEV in Estonian domestic pig and wild boar populations, as well as in humans who have direct regular contact with these animals. Our results suggest that HEV infections are present in Estonia and require attention.

Surveillance of hepatitis E virus contamination in shellfish in China

Background: Hepatitis E virus (HEV) has been confirmed to be a zoonotic virus of worldwide distribution. HEV contamination in the water environment has not been well examined in China. The objective of this study was to evaluate HEV contamination in shellfish in a coastal area of China. Such contamination would be significant for evaluating public health risks. Methods: samples of three species shellfish were collected from thirteen points of estuarine tidal flats around the Bohai Gulf and screened for HEV RNA using an in-house nested RT-PCR assay. The detected HEV-positive samples were further verified by gene cloning and sequencing analysis. Results: the overall HEV-positive detection rate is approximately 17.5% per kilogram of shellfish.  HEV was more common among S. subcrenata (28.2%), followed by A. granosa (14.3%) and R. philippinarum (11.5%). The phylogenetic analysis of the 13 HEV strains detected revealed that gene fragments fell into two known 4 sub-genotypes (4b/4d) groups and another unknown group. Conclusions: 13 different sub-genotype 4 HEVs were found in contaminated shellfish in the Bohai Gulf rim. The findings suggest that a health risk may exist for users of waters in the Bonhai area and to consumers of shellfish.  Further research is needed to assess the sources and infectivity of HEV in these settings, and to evaluate additional shellfish harvesting areas.

Environmentally Transmitted Pathogens

This chapter describes a variety of pathogens found in the environment that are capable of infecting humans and causing disease. Different classes of pathogens are discussed including bacteria, parasites and viruses. For each pathogen, data are provided on the incidence of the organism in a particular environmental matrix such as water, food or municipal waste. In addition, we discuss: the disease caused by the particular microbe; the mode of transmission; the incubation time needed within the host prior to the onset of disease; and the duration of illness. Fate and transport of pathogens in the environment are also described. A variety of bacterial pathogens are discussed including waterborne and waterbased bacteria. Parasites discussed include protozoa, nematodes, cestodes and trematodes. For viruses, both enteric and respiratory viruses are included.

Hepatitis E virus infections in humans and animals

Hepatitis E has traditionally been considered an endemic disease of developing countries. It generally spreads through contaminated water. However, seroprevalence studies have shown that hepatitis E virus (HEV) infections are not uncommon in industrialized countries. In addition, the number of autochthonous hepatitis E cases in these countries is increasing. Most HEV infections in developed countries can be traced to the ingestion of contaminated raw or undercooked pork meat or sausages. Several animal species, including pigs, are known reservoirs of HEV that transmit the virus to humans. HEVs are now recognized as an emerging zoonotic agent. In this review, we describe the general characteristics of HEVs isolated from humans and animals, the risk factors for human HEV infection, and the current status of human vaccine development.

Infectivity of a genotype 4 hepatitis E virus cDNA clone by intrahepatic inoculation of laboratory rats

A cDNA clone of a genotype 4 swine hepatitis E virus (HEV) strain (SAAS-FX17), identified in Shanghai, has been constructed. Capped RNA transcripts were prepared in vitro and shown to be replication-competent in Huh7 cells. Sprague-Dawley (SD) rats administered the RNA transcripts by intrahepatic inoculation developed active infections as evidenced by fecal virus shedding and sero-conversion to anti-HEV. The former was first detected between 23 and 30 days post-inoculation (dpi) and persisted until 45 dpi. Sera of rats inoculated with RNA transcripts became anti-HEV positive between 30 and 40 dpi, and reverted to anti-HEV negative at 52 dpi. Our data indicate for the first time that intrahepatic inoculation of rats with RNA transcripts of an HEV cDNA clone may serve as an alternative animal model for HEV research.

Structural basis for the neutralization and genotype specificity of hepatitis E virus

Hepatitis E virus (HEV) causes acute hepatitis in humans, predominantly by contamination of food and water, and is characterized by jaundice and flu-like aches and pains. To date, no vaccines are commercially available to prevent the disease caused by HEV. Previously, we showed that a monoclonal antibody, 8C11, specifically recognizes a neutralizing conformational epitope on HEV genotype I. The antibody 8C11 blocks the virus-like particle from binding to and penetrating the host cell. Here, we report the complex crystal structure of 8C11 Fab with HEV E2s(I) domain at 1.9 Å resolution. The 8C11 epitopes on E2s(I) were identified at Asp(496)-Thr(499), Val(510)-Leu(514), and Asn(573)-Arg(578). Mutations and cell-model assays identified Arg(512) as the most crucial residue for 8C11 interaction with and neutralization of HEV. Interestingly, 8C11 specifically neutralizes HEV genotype I, but not the other genotypes. Because HEV type I and IV are the most abundant genotypes, to understand this specificity further we determined the structure of E2s(IV) at 1.79 Å resolution and an E2s(IV) complex with 8C11 model was generated. The comparison between the 8C11 complexes with type I and IV revealed the key residues that distinguish these two genotypes. Of particular interest, the residue at amino acid position 497 at the 8C11 epitope region of E2s is distinct among these two genotypes. Swapping this residue from one genotype to another inversed the 8C11 reactivity, demonstrating the essential role played by amino acid 497 in the genotype recognition. These studies may lead to the development of antibody-based drugs for the specific treatment against HEV.

Environmentally Transmitted Pathogens

Pathogenic microorganisms usually originate from an infected host or directly from the environment; however, only a small proportion of these microbes cause infection. This chapter discusses the pathogens that are transmitted through the environment such as bacteria, viruses, and protozoa. Many human pathogens can be transmitted only by direct or close contact with an infected person or animal such as herpesvirus. Virus transmission by the airborne route may be both direct and indirect inhalation of infectious droplets or through contact with contaminated fomites. Water-borne diseases—such as yellow fever, dengue, filariasis, malaria, onchocerciasis, and sleeping sicknessare transmitted by insects that breed in water or live near water. The common bacterial pathogens transmitted through water include Salmonella, Escherichia coli, Shigella, Campylobacter, Yersinia, Vibrio, Helicobacter, and Legionella. Opportunistic pathogens are also numerous in the environment, and the most important opportunistic pathogen is Pseudomonas aeruginosa. Viruses are a leading cause of gastroenteritis and water-borne outbreaks may be caused by norovirus, hepatitis A virus, Coxsackie virus, echovirus, and adenoviruses. Respiratory diseases are also associated with a large number of viruses such as rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus (RSV), influenza virus, and adenovirus. Generally, viral and protozoan pathogens survive longer in the environment than enteric bacterial pathogens.

Health risks of enteric viral infections in children

Children are at a greater risk of infections from serious enteric viral illness than adults for a number of reasons. Most important is the immune system, which is needed to control the infection processes. This difference can lead to more serious infections than in adults, who have fully developed immune systems. There are a number of significant physiological and behavioral differences between adults and children that place children at a greater risk of exposure and a greater risk of serious infection from enteric viruses. Although most enteric viruses cause mild or asymptomatic infections, they can cause a wide range of serious and life-threatening illnesses in children. The peak incidence of most enteric viral illnesses is in children <2yr of age, although all age groups of children are affected. Most of these infections are more serious and result in higher mortality in children than adults. The fetus is also affected by enterovirus and infectious hepatitis resulting in significant risk of fetal death or serious illness. In addition to the poliovirus vaccine, the only vaccine available is for hepatitis A virus (HAV). A vaccine for rotavirus has currently been withdrawn, pending review because of potential adverse effects in infants. No specific treatment is available for the other enteric viruses. Enteric viral infections are very common in childhood. Most children are infected with rotavirus during the first 2yr of life. The incidence of enteroviruses and the viral enteric viruses ranges from 10% to 40% in children and is largely dependent on age. On average, half or more of the infections are asymptomatic. The incidence of hepatitis A virus is much lower than the enteric diarrheal viruses. There is no current evidence for hepatitis E virus (HEV) acquisition in children in the U.S. Enteric viral diseases have a major impact on direct and indirect health care costs (i.e., lost wages) and amount to several billion dollars a year in the U.S. Total direct and indirect costs for nonhospitalized cases may run from $88/case for Norwalk virus to $1,193/case for enterovirus aseptic meningitis. Direct costs of hospitalization ran from $887/case for Norwalk virus to $86,899/case for hepatitis A. These costs are based on 1997-1999 data. Generally, attack rates during drinking water outbreaks are greater for children than adults. The exception appears to be hepatitis E virus where young adults are more affected. However, pregnant women suffer a high mortality, resulting in concurrent fetal death. Also, secondary attack rates are much higher among children, probably because of fewer sanitary habits among this age group. Overall, waterborne outbreaks of viral disease have a greater impact among children than adults. To better quantify the impact on children, the literature hould be further reviewed for case studies of waterborne outbreaks where data are available on the resulting illness by age group. The EPA and/or Centers for Disease Control should attempt to collect these data as future outbreaks are documented.

Prevalence of hepatitis E virus antibodies in Canadian swine herds and identification of a novel variant of swine hepatitis E virus

Swine hepatitis E virus is a newly identified potentially zoonotic virus from pigs of particular concern for possible direct transmission to a human xenotransplant recipient by organ transplantation. In the present study, prevalence of serum antibodies to hepatitis E virus was examined in Canadian swine herds. A total of 998 serum samples collected from 6-month-old healthy slaughter hogs were examined by enzyme immunoassay and Western blot analysis for antibodies to the recombinant open reading frame 3 (ORF3) protein of hepatitis E virus expressed in Escherichia coli. These samples represented more than 80 different swine production units from five major swine-producing provinces across Canada. From this study, 594 samples (59.4%) were found to be positive for hepatitis E virus antibody. The seroprevalence was higher in Quebec (88.8%) and Ontario (80.1%) than in Alberta and Saskatchewan (38.3%). By PCR using a pair of oligonucleotide primers deduced from the ORF2 sequence of human hepatitis E virus, a specific hepatitis E virus sequence was recovered from feces of pigs. The nucleotide sequence identity between the U.S. swine hepatitis E virus and the Canadian isolate (SK3) was only 85.8%, suggesting that genotypic variations may exist in swine hepatitis E virus in North America. Among 165 serum samples collected from humans in Saskatchewan, 2.4% were found to be positive for antibodies to the hepatitis E virus ORF3 protein. Our data indicate that hepatitis E virus is highly prevalent in commercial swine populations in Canada and support the suggestion that the swine hepatitis E virus may be an important zoonotic agent for humans.

Evidence of extrahepatic sites of replication of the hepatitis E virus in a swine model

Hepatitis E virus (HEV) is the major cause of enterically transmitted non-A, non-B hepatitis in many developing countries and is also endemic in many industrialized countries. Due to the lack of an effective cell culture system and a practical animal model, the mechanisms of HEV pathogenesis and replication are poorly understood. Our recent identification of swine HEV from pigs affords us an opportunity to systematically study HEV replication and pathogenesis in a swine model. In an early study, we experimentally infected specific-pathogen-free pigs with two strains of HEV: swine HEV and the US-2 strain of human HEV. Eighteen pigs (group 1) were inoculated intravenously with swine HEV, 19 pigs (group 2) were inoculated with the US-2 strain of human HEV, and 17 pigs (group 3) were used as uninoculated controls. The clinical and pathological findings have been previously reported. In this expanded study, we aim to identify the potential extrahepatic sites of HEV replication using the swine model. Two pigs from each group were necropsied at 3, 7, 14, 20, 27, and 55 days postinoculation (DPI). Thirteen different types of tissues and organs were collected from each necropsied animal. Reverse transcriptase PCR (RT-PCR) was used to detect the presence of positive-strand HEV RNA in each tissue collected during necropsy at different DPI. A negative-strand-specific RT-PCR was standardized and used to detect the replicative, negative strand of HEV RNA from tissues that tested positive for the positive-strand RNA. As expected, positive-strand HEV RNA was detected in almost every type of tissue at some time point during the viremic period between 3 and 27 DPI. Positive-strand HEV RNA was still detectable in some tissues in the absence of serum HEV RNA from both swine HEV- and human HEV-inoculated pigs. However, replicative, negative-strand HEV RNA was detected primarily in the small intestines, lymph nodes, colons, and livers. Our results indicate that HEV replicates in tissues other than the liver. The data from this study may have important implications for HEV pathogenesis, xenotransplantation, and the development of an in vitro cell culture system for HEV.

HEV identified in serum from humans with acute hepatitis and in sewage of animal origin in Spain

BACKGROUND/AIMS

Hepatitis E virus (HEV) is an enterically transmitted pathogen that appears sporadically in non-endemic countries. We studied HEV as a causal agent of acute hepatitis cases in the Spanish population, and the role of pigs as an animal reservoir.

METHODS

The presence of HEV-RNA was analysed by nested polymerase chain reaction in 37 serum samples from patients with acute viral hepatitis, 48 porcine serum samples, 6 pig faecal samples and 12 slaughter-house sewage samples. Presence of antibodies was also tested in porcine sera.

RESULTS

HEV-RNA was found in 3 human serum samples from patients presenting IgG anti-HEV antibodies. Nucleotide sequence analysis identified 2 strains with 93.4% identity, phylogenetically most closely related to the Greece1 isolate, and more closely related to North American and other European strains than to those from endemic regions. HEV-RNA was also detected in slaughterhouse sewage mainly from pigs, presenting 92-94% nucleotide similarity compared to the strains detected in the human sera. Twenty-five per cent of the pigs tested presented IgG anti-HEV antibodies.

CONCLUSIONS

These data suggest that the HEV could be more widespread than previously thought, and present new evidence of the close relationship between HEV strains detected in pigs and those from acute hepatitis patients.

Prevalence of antibodies against hepatitis A and E viruses among rural populations of the Chaco region, south-eastern Bolivia

We conducted a cross-sectional study to determine the seroprevalence of antibodies against hepatitis A and hepatitis E viruses (HAV and HEV) in the population of two rural areas, Camiri and Villa Montes, of the Chaco region, south-eastern Bolivia. HAV antibodies were detected in 461 (94.1%) of 490 serum samples tested, not differing significantly between sexes and study areas. The HAV seropositivity rate (64.7%) was high even in the youngest age group (1-5 years). The prevalence of HEV was 7.3%, with no significant differences between sexes. The prevalence of HEV antibodies in the population of the Camiri area (10.4%) was significantly higher than in the Villa Montes area (4.4%), possibly due to the better quality of drinking water in the Villa Montes area. In the population </= 30 years of age, the HEV seropositivity rate (4.4%) was significantly lower than in the >/= 31 year-old group. This is consistent with findings in other countries. This is the first report of the prevalence of HEV infection in Bolivia.

Hepatitis E in Damascus, Syria

A hospital-based study of acute hepatitis was conducted in Damascus, Syria, from 1995 to 1998. One hundred ninety-three sera from defined acute hepatitis cases were screened by ELISA for IgM anti-HAV, HBsAg, IgM anti-HBc and anti-HCV. Serum samples negative for all markers indicating recent infection by hepatitis A, B, or C were tested for HEV markers. Overall, 47 cases (24.4%) had no detectable hepatitis markers (non-A-E). HAV infection was detected in 71.2% of all viral hepatitis cases. Acute hepatitis B and C constituted 24 and 1.4% of the cases, respectively. Only five cases of acute hepatitis E were noted. Of 47 patients who had non-A-E hepatitis, fifteen (31.9%) tested positive for IgG anti HEV. This study provides indirect evidence that HEV is very likely to be endemic in Damascus, Syria. It reports for the first time the occurrence of hepatitis E in the country, a health problem that should be investigated further.

Characterization of a strain of infectious hepatitis E virus isolated from sewage in an area where hepatitis E is not endemic

Raw sewage samples from an area where hepatitis E is not endemic (Barcelona, Spain) were analyzed by reverse transcriptase-PCR followed by nested PCR. One of the 37 tested samples showed a positive result for hepatitis E virus (HEV). The detected strain was amplified by inoculation into rhesus monkeys, and the course of the infection was studied by analyzing serological and biochemical parameters and by monitoring the presence of HEV in serum and feces. Fecal suspensions from the rhesus monkeys were used as the source of viral particles for sequence analysis. Eighty percent of the genome of the isolated strain, named BCN, was sequenced and found to be phylogenetically related to Asian (Indian) strains, with a 98% nucleotide identity with an isolate from Madras, India. Since this was a single isolation we cannot conclude that HEV is regularly present in the sewage. However, the finding of viable HEV in sewage has implications for contamination of the environment and shellfish by HEV and must be considered in the diagnosis of viral hepatitis in regions of nonendemic hepatitis.

Hepatitis E virus infection in north-east Italy: serological study in the open population and groups at risk

Developed western countries are considered to be relatively free from endemic foci of hepatitis E virus (HEV) infections. The aim of this study was to assess the seroepidemiology of HEV in north-east Italy. Of the 2361 individuals studied 1889 were representative of the general population and 472 were from groups at high risk for viral infections: 279 drug users and 193 patients on chronic haemodialysis. All sera were tested for hepatitis C virus antibody (HCVAb), human immunodeficiency virus antibody (HIVAb) and for hepatitis B virus (HBV) serology. Two solid-phase enzyme-linked immunosorbent assays (ELISA) were used to study the seroepidemiology of HEV IgG, the first (using recombinant antigens) for confirmation of initially reactive samples. The prevalence of circulating hepatitis E virus antibody (HEVAb) was 2.6% in the open population, 5.4% among drug users and 9.3% among patients on chronic haemodialysis. In the open population a positive relationship between age and prevalence of HEVAb was observed. A relationship between presence of HEVAb and serological evidence of previous HBV or HCV infections was also observed in this study. It was concluded that HEV infections are present in north-east Italy and are more frequent among subjects at risk for blood-borne viral infections. The positive correlation, observed in the open population, between age and prevalence of HEVAb suggests the presence of a cohort effect.

Serological evidence for hepatitis E virus infection in Israel

Israel is suspected to be endemic for hepatitis E virus (HEV) because of its geographic location and the large-scale immigration from endemic countries. Although no cases of local HEV infection have been diagnosed, a serological survey would provide indirect evidence for such infection. We examined sera from 1,416 healthy subjects, including 1,139 Jews from various regions of Israel and 277 Arabs, most of whom reside in the West Bank of the Jordan River. In addition, we tested 13 non-A, non-B, and non-C viral hepatitis patients. Sera were screened for antibody to hepatitis E virus (anti-HEV) by a newly developed enzyme immunoassay (EIA) and by immunoblots for both IgG and IgM anti-HEV activity. Positive samples were confirmed by neutralization. The seroprevalence found by EIA was 2.81% and 1.81% in the Jewish and Arab populations, respectively. More than a 2-fold higher prevalence in males compared to females and an increase with age were found in both populations. However, these differences were nonsignificant. The geographical distribution was even throughout the country, except for two clusters of 3 and 4 seropositive individuals possibly reflecting past foci of infection. Eight of 37 EIA-positive sera were positive for IgG, and 3 were positive for IgM by the immunoblot assay. Among hepatitis patients (9 acute and 4 chronic), one patient with chronic hepatitis was positive for both IgG and IgM. Our study provides indirect evidence that Israel is endemic for HEV.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatitis E seroprevalence in selected individuals in South Africa

Antibodies to the hepatitis E virus (HEV) were detected by an enzyme immunoassay using synthetic HEV peptides. Positive anti-HEV results were confirmed by a neutralization assay and Western blot analysis. Anti-HEV was detected in 10 of 555 canoeists (1.8%) with regular exposure to sewage-polluted water and in 6 of 227 (2.6%) medical students with minimal exposure. The overall prevalence of 16 per 782 individuals (2.05%) suggests that HEV may be endemic in South Africa. This is confirmed by indications of infection earlier than the third decade of life, and by individuals with anti-HEV who had rarely or never been out of the country. The prevalence data suggest that regular exposure to sewage-polluted water was not a particular risk factor. None of the individuals with anti-HEV had a history of clinical hepatitis E, suggesting sporadic low level subclinical cases of infection. This is in agreement with the absence of reports on clinical cases or outbreaks of hepatitis E in South Africa.