Detection of hepatitis E virus in raw and treated wastewater with the polymerase chain reaction

Wastewater-Based Epidemiology for Early Detection of Viral Outbreaks

The immense global burden of infectious disease outbreaks and the need to establish prediction and prevention systems have been recognized by the World Health Organization (WHO), the National Institutes of Health (NIH), the United States Agency of International Development (USAID), the Bill and Melinda Gates Foundation, and the international scientific community. Despite multiple efforts, this infectious burden is still increasing. For example, it has been reported that between 1.5 and 12 million people die each year from waterborne diseases and diarrheal diseases are listed within the top 15 leading causes of death worldwide. Rapid population growth, climate change, natural disasters, immigration, globalization, and the corresponding sanitation and waste management challenges are expected to intensify the problem in the years to come.

Transmission of hepatitis E virus by water: An issue still pending in industrialized countries

Hepatitis E virus (HEV) is an enteric virus divided into eight genotypes. Genotype 1 (G1) and G2 are specific to humans; G3, G4 and G7 are zoonotic genotypes infecting humans and animals. Transmission to humans through water has been demonstrated for G1 and G2, mainly in developing countries, but is only suspected for the zoonotic genotypes. Thus, the water-related HEV hazard may be due to human and animal faeces. The high HEV genetic variability allows considering the presence in wastewater of not only different genotypes, but also quasispecies adding even greater diversity. Moreover, recent studies have demonstrated that HEV particles may be either quasi-enveloped or non-enveloped, potentially implying differential viral behaviours in the environment. The presence of HEV has been demonstrated at the different stages of the water cycle all over the world, especially for HEV G3 in Europe and the USA. Concerning HEV survival in water, the virus does not have higher resistance to inactivating factors (heat, UV, chlorine, physical removal), compared to viral indicators (MS2 phage) or other highly resistant enteric viruses (Hepatitis A virus). But the studies did not take into account genetic (genogroups, quasispecies) or structural (quasi- or non-enveloped forms) HEV variability. Viral variability could indeed modify HEV persistence in water by influencing its interaction with the environment, its infectivity and its pathogenicity, and subsequently its transmission by water. The cell culture methods used to study HEV survival still have drawbacks (challenging virus cultivation, time consuming, lack of sensitivity). As explained in the present review, the issue of HEV transmission to humans through water is similar to that of other enteric viruses because of their similar or lower survival. HEV transmission to animals through water and how the virus variability affects its survival and transmission remain to be investigated.

Hepatitis E virus in lettuce and water samples: A method-comparison study

The hepatitis E virus (HEV), which is an increasing cause of acute viral hepatitis in Europe, is a zoonotic virus that is mainly transmitted through contaminated water, consumption of raw or undercooked meat from pigs or wild boar, blood transfusion, and organ transplantation. Although the role of HEV transmission through contaminated produce has not been confirmed, the presence of HEV has been reported in irrigation waters and in vegetables. The present study used a World Health Organization (WHO) international standard and clinical samples to evaluate the performance characteristics of three RT-qPCR assays for detection and quantification of HEV. Two of the evaluated assays provided good analytical sensitivity, as 250 international units (IU) per ml could be detected. Then, experiments focused on evaluating the elution conditions suitable for HEV release from vegetables, with the method proposed by the ISO 15216:2017 selected for evaluation in three types of fresh vegetables. The concentration method proposed by the ISO 15216:2017 combined with the RT-qPCR described by Schlosser et al. (2014) resulted in average HEV recoveries of 1.29%, 0.46%, and 3.95% in lettuce, spinach, and pepper, respectively, with an average detection limit of 1.47 × 105 IU/25 g. In naturally contaminated samples, HEV was detected in sewage only (10/14), while no detection was reported in lettuce (0/36) or in irrigation water samples (0/24).

Laboratory challenges in the diagnosis of hepatitis E virus

Hepatitis E virus (HEV) is an RNA virus that is an important cause of both acute and chronic hepatitis worldwide. To date, there are eight HEV genotypes that can infect mammals. HEV-1 and HEV-2 infect exclusively humans, while HEV-3 and HEV-4 infect humans and various animals, mainly pigs and deer. Additionally, two new genotypes (HEV-5 and HEV-6) infect mainly wild boar. Recently, newly discovered genotypes HEV-7 and HEV-8 were found to infect camels and possibly humans. Nevertheless, the epidemiological distribution of HEV-7 is not well established. HEV-8 is another newly discovered genotype that was identified in 2016 in Chinese Bactrian camels. Although faecal-oral transmission is the most common route of HEV transmission, HEV can be vertically transmitted from infected mothers to their fetuses. HEV may also spread by zoonotic transmission from infected animals to humans and through person-to-person contact. Nowadays, since the number of reported cases linked to blood donations is increasing annually, HEV is recognized as a transfusion-transmitted virus. Laboratory diagnostic techniques vary in their specificity and sensitivity for HEV detection. Direct techniques allow for detection of the viral proteins, antigens and viral nucleic acid, while HEV-specific IgG and IgM antibodies can help establish a diagnosis in acute and chronic infections. In this review, we will discuss recent technologies in the laboratory diagnosis of HEV, including serological and molecular methods to assess the specificity and sensitivity of currently available HEV commercial assays.

Assessment and Evaluation of an Integrated Hybrid Anaerobic-Aerobic Sewage Treatment System for the Removal of Enteric Viruses

The capability of a cost-effective and a small size decentralized pilot wastewater treatment plant (WWTP) to remove enteric viruses such as rotavirus, norovirus genogroup I (GGI), norovirus genogroup II (GGII), Hepatitis E virus (HEV), and adenovirus was studied. This pilot plant is an integrated hybrid anaerobic/aerobic setup which consisted of anaerobic sludge blanket (UASB), biological aerated filter (BAF), and inclined plate settler (IPS). Both the UASB and BAF are packed with a non-woven polyester fabric (NWPF). Results indicated that the overall log₁₀ reductions of enteric viruses' genome copies through the whole system were 3.1 ± 1, 3.3 ± 0.5, and 2.6 ± 0.9 log₁₀ for rotavirus, norovirus GGI, and adenovirus, respectively. Reduction efficiency for both norovirus GGII and HEV after the different treatment steps could not be calculated because there were no significant numbers of positive samples for both viruses. The overall reduction of rotavirus infectious units through the whole system was 2.2 ± 0.8 log₁₀ reduction which is very close to the overall log₁₀ reduction of adenovirus infectious units through the whole system which was 2.1 ± 0.8 log₁₀ reduction. There was no considerable difference in the removal efficiency for different rotavirus G and P types. Adenovirus 41 was the only type detected in the all positive samples. Although the pilot WWTP investigated is cost effective, has a small footprint, does not need a long distance network pipes, and easy to operate, its efficiency to remove enteric viruses is comparable with the conventional centralized WWTPs.

Transmission of Hepatitis E Virus in Developing Countries

Hepatitis E virus (HEV), an RNA virus of the Hepeviridae family, has marked heterogeneity. While all five HEV genotypes can cause human infections, genotypes HEV-1 and -2 infect humans alone, genotypes HEV-3 and -4 primarily infect pigs, boars and deer, and genotype HEV-7 primarily infects dromedaries. The global distribution of HEV has distinct epidemiological patterns based on ecology and socioeconomic factors. In resource-poor countries, disease presents as large-scale waterborne epidemics, and few epidemics have spread through person-to-person contact; however, endemic diseases within these countries can potentially spread through person-to-person contact or fecally contaminated water and foods. Vertical transmission of HEV from infected mother to fetus causes high fetal and perinatal mortality. Other means of transmission, such as zoonotic transmission, can fluctuate depending upon the region and strain of the virus. For instance, zoonotic transmission can sometimes play an insignificant role in human infections, such as in India, where human and pig HEV infections are unrelated. However, recently China and Southeast Asia have experienced a zoonotic spread of HEV-4 from pigs to humans and this has become the dominant mode of transmission of hepatitis E in eastern China. Zoonotic HEV infections in humans occur by eating undercooked pig flesh, raw liver, and sausages; through vocational contact; or via pig slurry, which leads to environmental contamination of agricultural products and seafood. Lastly, blood transfusion-associated HEV infections occur in many countries and screening of donors for HEV RNA is currently under serious consideration. To summarize, HEV genotypes 1 and 2 cause epidemic and endemic diseases in resource poor countries, primarily spreading through contaminated drinking water. HEV genotypes 3 and 4 on the other hand, cause autochthonous infections in developed, and many developing countries, by means of a unique zoonotic food-borne transmission.

Human and Animal Viruses in Food (Including Taxonomy of Enteric Viruses)

In recent years, there has been an increase in the incidence of foodborne diseases worldwide, with viruses now being recognized as a major cause of these illnesses. The most common viruses implicated in foodborne disease are enteric viruses, which are found in the human gastrointestinal tract, excreted in human feces and transmitted by the fecal-oral route. Many different viruses are found in the gastrointestinal tract but not all are recognized as foodborne pathogens. The diseases caused by enteric viruses fall into three main types: gastroenteritis, enterically transmitted hepatitis, and illnesses that can affect other parts of the body such as the eye, the respiratory system and the central nervous system leading to conjunctivitis, poliomyelitis, meningitis and encephalitis. Viral pathogens excreted in human feces include noroviruses, sapoviruses, enteroviruses, adenoviruses, hepatitis A virus (HAV), hepatitis E virus (HEV), rotaviruses, and astroviruses. Most of these viruses have been associated with foodborne disease outbreaks. Noroviruses and HAV are commonly identified as foodborne causes of gastroenteritis and acute hepatitis, respectively.

Hepatitis E virus as an emerging zoonotic pathogen

Hepatitis E outbreaks are a serious public health concern in developing countries. The disease causes acute infections, primarily in young adults. The mortality rate is approximately 2%; however, it can exceed 20% in pregnant women in some regions in India. The causative agent, hepatitis E virus (HEV), has been isolated from several animal species, including pigs. HEV genotypes 3 and 4 have been isolated from both humans and animals, and are recognized as zoonotic pathogens. Seroprevalence studies in animals and humans indirectly suggest that HEV infections occur worldwide. The virus is primarily transmitted to humans via undercooked animal meats in developed countries. Moreover, transfusion- and transplantation-mediated HEV infections have recently been reported. This review summarizes the general characteristics of hepatitis E, HEV infection status in animals and humans, the zoonotic transmission modes of HEV, and HEV vaccine development status.

The use of human sewage screening for community surveillance of hepatitis E virus in the UK

Hepatitis E virus sequences were detected by RT‐PCR in 14/15 (93%) of untreated sewage samples from Edinburgh, Scotland, UK. Phylogenetic analysis of amplicons at limiting dilution revealed the co‐circulation of multiple variants of HEV‐3, with a pattern of diversity matching that observed in a local cohort of HEV‐infected hepatitis patients. J. Med. Virol. 88:915–918, 2016. © 2015 The Authors. Journal of Medical Virology Published by Wiley Periodicals, Inc.

Hepatitis E virus: foodborne, waterborne and zoonotic transmission

Hepatitis E virus (HEV) is responsible for epidemics and endemics of acute hepatitis in humans, mainly through waterborne, foodborne, and zoonotic transmission routes. HEV is a single-stranded, positive-sense RNA virus classified in the family Hepeviridae and encompasses four known Genotypes (1–4), at least two new putative genotypes of mammalian HEV, and one floating genus of avian HEV. Genotypes 1 and 2 HEVs only affect humans, while Genotypes 3 and 4 are zoonotic and responsible for sporadic and autochthonous infections in both humans and several other animal species worldwide. HEV has an ever-expanding host range and has been identified in numerous animal species. Swine serve as a reservoir species for HEV transmission to humans; however, it is likely that other animal species may also act as reservoirs. HEV poses an important public health concern with cases of the disease definitively linked to handling of infected pigs, consumption of raw and undercooked animal meats, and animal manure contamination of drinking or irrigation water. Infectious HEV has been identified in numerous sources of concern including animal feces, sewage water, inadequately-treated water, contaminated shellfish and produce, as well as animal meats. Many aspects of HEV pathogenesis, replication, and immunological responses remain unknown, as HEV is an extremely understudied but important human pathogen. This article reviews the current understanding of HEV transmission routes with emphasis on food and environmental sources and the prevalence of HEV in animal species with zoonotic potential in humans.

Detection of enteropathogens by PCR

The widespread problem of contaminated water by enteric microorganisms necessitates the need to develop a rapid protocol to detect pathogens in water bodies. Usual methods like plating, biochemical tests and use of DNA probes are time consuming which is a limiting factor especially in epidemic situations. Moreover, some cells can exist in a virulent viable but non-culturable state making detection very difficult by plating method. This paper describes a rapid method to detect the enteropathogens,E.coli, Salmonella andVibrio and enteric viruses from water samples by Polymerase Chain Reaction.E.coli was specially chosen as it is an indicator of fecal contamination. The sensitivity ofE.coli detection was improved to 10 cells to keep in tune with the WHO guidelines. The presence ofE.coli would also indicate the probable presence of other pathogens.

Enteric hepatitis viruses

Hepatitis viruses are infectious agents that can infect liver and cause inflammation. The infection triggers immune response against infected cells that leads to the destruction of hepatic cells. This destruction has two consequences: leaking ALT and AST liver enzymes which increases during the course of disease and accumulation of bilirubin- a red pigmented compound released from dead red cells- which causes the yellow coloration of eyes and skin. These viruses transmit through diverse routes i.e. blood transfusion, sexual contacts and consuming water or food contaminated by feces. Enteric hepatitis viruses use the latter route for transmission; hence their outbreaks are more common in underdeveloped countries. There are currently two distinguished enteric hepatitis viruses, hepatitis A and hepatitis E. These viruses belong to different family of viruses and their epidemiological characteristics are different. These infections can be diagnosed by an ELISA for IgM antibody. A vaccine has been developed in last decade of twentieth century for hepatitis A virus, which is administered mostly in the developed world i.e. U.S and Japan. Treatment for these infections is mostly supportive; however, in the case of fulminant hepatitis the liver transplantation might be necessary.

Hepatitis E: Epidemiology and prevention

Hepatitis E is caused by the hepatitis E virus (HEV), the major etiologic agent of enterically transmitted non-A hepatitis worldwide. HEV is responsible for major outbreaks of acute hepatitis in developing countries, especially in many parts of Africa and Asia. The HEV is a spherical, non-enveloped, single-stranded, positive sense RNA virus that is approximately 32 nm to 34 nm in diameter and is the only member in the family Hepeviridae and genus Hepevirus. There are four distinct genotypes of HEV (genotypes 1-4). While genotype 1 is predominantly associated with large epidemics in developing countries, genotype 3 has recently emerged as a significant pathogen in developed countries. The clinical manifestations and the laboratory abnormalities of hepatitis E are not distinguishable from that caused by other hepatitis viruses. However, high mortality among pregnant women particularly during the third trimester distinguishes HEV from other causes of acute viral hepatitis. Specific etiologic diagnosis among infected cases can be made by serological testing or detection of viral nucleic acid by reverse transcription polymerase chain reaction. Although there are vaccine candidates that had been shown to be safe and efficacious in clinical trials, none are approved currently for use. There is no specific therapy for acute hepatitis E as treatment remains supportive.

Presence of enteric hepatitis viruses in the sewage and population of Greater Cairo

In Egypt, the disease burden of viral hepatitis is one of the heaviest worldwide. We conducted a survey of hepatitis A virus (HAV) and hepatitis E virus (HEV) in patients and sewage in Cairo. Our data showed that HAV (genotype IB) was predominant over HEV (genotype 3) and was circulating in the population and the environment.

From barnyard to food table: the omnipresence of hepatitis E virus and risk for zoonotic infection and food safety

Hepatitis E virus (HEV) is an important but extremely understudied pathogen. The mechanisms of HEV replication and pathogenesis are poorly understood, and a vaccine against HEV is not yet available. HEV is classified in the family Hepeviridae consisting of at least four recognized major genotypes. Genotypes 1 and 2 HEV are restricted to humans and associated with epidemics in developing countries, whereas genotypes 3 and 4 HEV are zoonotic and responsible for sporadic cases worldwide. The identification and characterization of a number of animal strains of HEV from pigs, chickens, rabbits, rats, mongoose, deer, and possibly cattle and sheep have significantly broadened the host range and diversity of HEV. The demonstrated ability of cross-species infection by some animal strains of HEV raises public health concerns for zoonotic HEV infection. Pigs are a recognized reservoir for HEV, and pig handlers are at increased risk of zoonotic HEV infection. Sporadic cases of hepatitis E have been definitively linked to the consumption of raw or undercooked animal meats such as pig livers, sausages, and deer meats. In addition, since large amounts of viruses excreted in feces, animal manure land application and runoffs can contaminate irrigation and drinking water with concomitant contamination of produce or shellfish. HEV RNA of swine origin has been detected in swine manure, sewage water and oysters, and consumption of contaminated shellfish has also been implicated in sporadic cases of hepatitis E. Therefore, the animal strains of HEV pose not only a zoonotic risk but also food and environmental safety concerns.

Development of a combined immunomagnetic separation and quantitative reverse transcription-PCR assay for sensitive detection of infectious rotavirus in water samples

A quantitative and rapid detection method for rotavirus in water samples was developed using immunomagnetic separation combined with quantitative reverse transcription-polymerase chain reaction (IMS-RT-qPCR). Magnetic beads coated with antibodies against representative group A rotavirus were used to capture and purify intact rotavirus particles in both artificial and real environmental water sample matrix. Compared to extracting RNA using commercial kits and RT-qPCR assay, the developed IMS-RT-qPCR method increased the detection sensitivity by about one order of magnitude when applied in clean water, with a detection limit of 3.16 50% tissue culture infectious dose (TCID(50))/mL within 5h. This method was compatible with various commonly used virus eluants, including beef extract (BE), beef extract with 0.05M glycine (BEG) and urea arginine phosphate buffer (UAPB). The recovery efficiencies from various eluants using IMS-RT-qPCR are higher than that using direct RT-qPCR method, demonstrating the effectiveness of the IMS step for eliminating inhibitors in the eluant matrix. This method was also successfully applied to purify and detect rotavirus particles seeded in 10(3)-fold concentrated wastewater influent samples. It seemed to reduce the interference from complex sample background and increase the qPCR product reliability comparing to RT-qPCR method without the IMS step. The results indicated that IMS-RT-qPCR is a rapid, sensitive and reliable tool for detecting rotaviruses in complex water environments.

Novel risk factors associated with hepatitis E virus infection in a large outbreak in northern Uganda: results from a case-control study and environmental analysis

An outbreak of hepatitis E virus (HEV) began in October 2007 in northern Uganda. To determine risk factors and sources for ongoing transmission, we conducted both a case-control study and an environmental investigation. A case patient was defined as having serologic evidence of HEV infection, whereas controls were seronegative. We identified risk factors for infection by univariable and multivariable analyses using conditional logistic regression. Several water sources were tested for HEV RNA. Among 112 cases and 145 controls, storage of drinking water in large-mouthed vessels (adjusted odds ratios [AOR] = 2.83; 95% confidence interval [CI] = 1.16-6.94) and washing hands in a group basin (AOR = 1.90; 95% CI = 1.07-3.38) were associated with HEV infection. HEV RNA was detected from communal hand-rinse and surface-water samples. The epidemiologic and environmental water-testing results suggest that household-level factors played an important role in the transmission of HEV-modalities that have been previously underappreciated.

Molecular epidemiology of hepatitis E virus in Hong Kong

Hepatitis E virus (HEV) is one of the major causes of acute and self-limiting hepatitis in human. In Hong Kong, the number of notifications increased from 26 to 62 from year 2001 to 2007. This study describes the molecular epidemiology of HEV in Hong Kong in order to determine the movement and distribution of HEV. HEV in 171 serum samples from HEV IgM positive cases from year 2001 to 2007 were amplified using RT-PCR and subjected to nucleotide sequencing. Phylogenetic analysis showed 162 of 171 HEV detected cases (94.7%) belonged to genotype IV and 8 (4.7%) to genotype I. Interestingly, a cluster of 10 cases in year 2007 that had the same sequence of HEV was identified. Epidemiological data however did not detect any relationship between these cases. Since zoonotic transmission is a well known route of HEV infection, close monitoring of the circulating HEV strains in human and food source animals may help to provide additional information on the transmission of HEV and possible source of infection in Hong Kong.

Long-term inactivation study of three enteroviruses in artificial surface and groundwaters, using PCR and cell culture

Since the transmission of pathogenic viruses via water is indistinguishable from the transmission via other routes and since the levels in drinking water, although significant for health, may be too low for detection, quantitative viral risk assessment is a useful tool for assessing disease risk due to consumption of drinking water. Quantitative viral risk assessment requires information concerning the ability of viruses detected in drinking water to infect their host. To obtain insight into the infectivity of viruses in relation to the presence of virus genomes, inactivation of three different enteroviruses in artificial ground and surface waters under different controlled pH, temperature, and salt conditions was studied by using both PCR and cell culture over time. In salt-peptone medium, the estimated ratio of RNA genomes to infectious poliovirus 1 in freshly prepared suspensions was about 10(0). At 4 degrees C this ratio was 10(3) after 600 days, and at 22 degrees C it was 10(4) after 200 days. For poliovirus 1 and 2 the RNA/infectious virus ratio was higher in artificial groundwater than in artificial surface water, but this was not the case for coxsackievirus B4. When molecular detection is used for virus enumeration, it is important that the fraction of infectious virus (based on all virus genomes detected) decays with time, especially at temperatures near 22 degrees C.

Hepatitis E: a complex and global disease

Thirty years after its discovery, the hepatitis E virus (HEV) continues to represent a major public health problem in developing countries. In developed countries, it has emerged as a significant cause of non-travel-associated acute hepatitis. HEV infects a wide range of mammalian species and a key reservoir worldwide appears to be swine. Genomic sequence similarity between some human HEV genotypes and swine HEV strains has been identified and we know that humans can acquire HEV infection from animals. Although for the most part the clinical course of HEV infection is asymptomatic or mild, significant risk of serious disease exists in pregnant women and those with chronic liver disease. In addition, there are data on the threat of chronic infections in immunocompromised patients. Beyond management of exposure by public health measures, recent data support that active immunisation can prevent hepatitis E, highlighting the need for vaccination programmes. Here we review the current knowledge on HEV, its epidemiology, and the management and prevention of human disease.

Presence of hepatitis E virus in sewage in Northern India: frequency and seasonal pattern

Outbreaks of acute hepatitis E, associated with consumption of contaminated drinking water, are frequent in India. Sewage is a major source for contamination of surface water. Data on the presence of hepatitis E virus (HEV) in sewage in India are limited. The aim of this study was to look for the presence of HEV RNA in concentrates of sewage specimens collected from a major open sewage drain in Lucknow, India during August 2004 to July 2006, by the polymerase chain reaction, using primers specific for human HEV (genotype 1) or Indian swine HEV (genotype 4). Of the 192 sewage specimens tested, 79 (41%) showed presence of human HEV RNA. The positivity rate was higher during the second year (52/103 [51%]) than during the first year (27/89 [30%]; P = 0.005). The seasonal pattern of HEV RNA positivity was as follows: winter months (November to February): 28 of 61 (46%); summer months (March to June): 36 of 66 (55%); and, monsoon months (July to October) 15 of 65 (23%). There was no reported outbreak of hepatitis E in the city during the study period. Swine HEV RNA was not detected in any of the 69 specimens tested. Repeat testing confirmed the reproducibility of the results. In addition, nucleic acid sequencing of six sewage isolates showed that these belonged to HEV genotype 1. The study suggests that HEV infection and fecal viral excretion may be common in HEV-endemic regions throughout the year even during non-epidemic periods.

Hepatitis E virus

Hepatitis E virus (HEV) is the aetiological agent of non-HAV enterically transmitted hepatitis. It is the major cause of sporadic as well as epidemic hepatitis, which is no longer confined to Asia and developing countries but has also become a concern of the developed nations. In the Indian subcontinent, it accounts for 30-60% of sporadic hepatitis. It is generally accepted that hepatitis E is mostly self-limited and never progresses to chronicity. It has a higher mortality in pregnant women where the disease condition is accentuated with the development of fulminant liver disease. Currently, no antiviral drug or vaccine is licensed for HEV, although a vaccine candidate is in clinical trials. HEV genome is 7.2kb in size with three open reading frames (ORFs) and 5' and 3' cis acting elements, which have important roles to play in HEV replication and transcription. ORF1 codes for methyl transferase, protease, helicase and replicase; ORF2 codes for the capsid protein and ORF3 for a protein of undefined function. HEV has recently been classified in the genus Hepevirus of the family Hepeviridae. There are four major recognised genotypes with a single known serotype. The absence of a reliable in vitro propagation system is an obstacle to deciphering HEV biology. The genome of HEV has been cloned, sequenced and the infectious nature of these replicons has been established. However, questions related to replication, transcription, virus-host interactions and pathogenesis remain to be answered. This comprehensive review summarises the progress made so far in HEV research, and addresses some of the unanswered questions.

Evaluation of methods used to concentrate and detect hepatitis A virus in water samples

Two adsorption-elution concentration methods, both involving negatively charged membranes, were evaluated in order to monitor hepatitis A virus (HAV) contamination in tap, river, mineral and coastal water samples: elution with urea-arginine phosphate buffer/reconcentration with magnesium chloride (method 1); and sodium hydroxide elution/reconcentration with a commercial concentrator (method 2). Nested (qualitative) reverse transcriptase PCR (RT-PCR) and real-time (quantitative) RT-PCR were used to detect and quantify HAV RNA in concentrated water samples. For concentrating HAV, method 1 was found to be the most suitable for tap water and method 2 most suitable for mineral water. HAV inoculated experimentally was detected in river water samples by both methods and in coastal water samples by neither method. The detection limits were 6 x 10(9) g equiv./ml for qualitative PCR and 60 g equiv./ml for quantitative PCR. In a field application study, HAV was detected in 20% of river and tap water samples but not in coastal or mineral water samples. River water samples contained subgenotype IA, and tap water samples contained subgenotype IB. It is concluded that, although influencing qualitative PCR, the concentration method does not affect quantitative PCR, which could therefore be used for all types of water samples. Both techniques are recommended for detecting HAV in environmental water samples.

Real-time nucleic acid sequence-based amplification assay for detection of hepatitis A virus

A nucleic acid sequence-based amplification (NASBA) assay in combination with a molecular beacon was developed for the real-time detection and quantification of hepatitis A virus (HAV). A 202-bp, highly conserved 5' noncoding region of HAV was targeted. The sensitivity of the real-time NASBA assay was tested with 10-fold dilutions of viral RNA, and a detection limit of 1 PFU was obtained. The specificity of the assay was demonstrated by testing with other environmental pathogens and indicator microorganisms, with only HAV positively identified. When combined with immunomagnetic separation, the NASBA assay successfully detected as few as 10 PFU from seeded lake water samples. Due to its isothermal nature, its speed, and its similar sensitivity compared to the real-time RT-PCR assay, this newly reported real-time NASBA method will have broad applications for the rapid detection of HAV in contaminated food or water.

A broadly reactive one-step real-time RT-PCR assay for rapid and sensitive detection of hepatitis E virus

Hepatitis E virus (HEV) is transmitted by the fecal-oral route and causes sporadic and epidemic forms of acute hepatitis. Large waterborne HEV epidemics have been documented exclusively in developing countries. At least four major genotypes of HEV have been reported worldwide: genotype 1 (found primarily in Asian countries), genotype 2 (isolated from a single outbreak in Mexico), genotype 3 (identified in swine and humans in the United States and many other countries), and genotype 4 (identified in humans, swine and other animals in Asia). To better detect and quantitate different HEV strains that may be present in clinical and environmental samples, we developed a rapid and sensitive real-time RT-PCR assay for the detection of HEV RNA. Primers and probes for the real-time RT-PCR were selected based on the multiple sequence alignments of 27 sequences of the ORF3 region. Thirteen HEV isolates representing genotypes 1-4 were used to standardize the real-time RT-PCR assay. The TaqMan assay detected as few as four genome equivalent (GE) copies of HEV plasmid DNA and detected as low as 0.12 50% pig infectious dose (PID50) of swine HEV. Different concentrations of swine HEV (120-1.2PID50) spiked into a surface water concentrate were detected in the real-time RT-PCR assay. This is the first reporting of a broadly reactive TaqMan RT-PCR assay for the detection of HEV in clinical and environmental samples.

Hepatitis E Vaccines

Hepatitis E accounts for the major part of enterally transmitted non-A, non-B hepatitis worldwide. Its agent, the hepatitis E virus (HEV), is a small, single-stranded RNA virus. Only one serotype of HEV is recognised. Infection results in protective immunity with long-lived neutralising antibodies. In developing countries with poor sanitary conditions and high population density, hepatitis E causes water-borne epidemics with substantial mortality rates in pregnant women. In addition, more than 50% of cases of acute hepatic failure and sporadic acute hepatitis are due to hepatitis E. The overall prevalence rates of antibodies to the HEV in populations native to these areas rarely exceed 25%. Hence, many individuals remain susceptible to hepatitis E infection, making hepatitis E an important public health concern. In this context, the development of an HEV vaccine is warranted. Because HEV does not grow adequately in cell cultures the development of a vaccine based on inactivated or attenuated whole-virus particles is not feasible. HEV vaccines currently under study are based on recombinant proteins derived from immunogenic parts of the HEV capsid gene. Other approaches such as DNA-based vaccines or transgenic tomatoes have also been developed. Several recombinant protein-based vaccines elicited neutralising antibodies and protective immunity in vaccinated non-human primates. One such vaccine has passed phase I trial and is currently under further evaluation in field trials. Even so, several questions remain to be answered before vaccination programmes could be implemented.

Pathogenic human viruses in coastal waters

This review addresses both historical and recent investigations into viral contamination of marine waters. With the relatively recent emergence of molecular biology-based assays, a number of investigations have shown that pathogenic viruses are prevalent in marine waters being impacted by sewage. Research has shown that this group of fecal-oral viral pathogens (enteroviruses, hepatitis A viruses, Norwalk viruses, reoviruses, adenoviruses, rotaviruses, etc.) can cause a broad range of asymptomatic to severe gastrointestinal, respiratory, and eye, nose, ear, and skin infections in people exposed through recreational use of the water. The viruses and the nucleic acid signature survive for an extended period in the marine environment. One of the primary concerns of public health officials is the relationship between the presence of pathogens and the recreational risk to human health in polluted marine environments. While a number of studies have attempted to address this issue, the relationship is still poorly understood. A contributing factor to our lack of progress in the field has been the lack of sensitive methods to detect the broad range of both bacterial and viral pathogens. The application of new and advanced molecular methods will continue to contribute to our current state of knowledge in this emerging and important field.

Development of a virus concentration method and its application to detection of enterovirus and norwalk virus from coastal seawater

We developed a new procedure for concentration of enteric viruses from water using a negatively charged membrane. Rinsing the membrane with 0.5 mM H(2)SO(4) (pH 3.0) in order to elute cations prior to viral elution with 1 mM NaOH (pH 10.5) promoted poliovirus recovery yields from 33 to 95% when applied to pure water and 38 to 89% when applied to natural seawater from Tokyo Bay, Japan, respectively. This method showed average recovery yields of spiked poliovirus of 62% (n = 8) from 1 liter of artificial seawater. This method showed higher recovery yields (>61%) than that of the conventional method using positively charged membrane (6%) when applied to seawater. This method is also free from beef extract elution, which has an inhibitory effect in the subsequent viral genome detection by reverse transcription-PCR. Naturally occurring Norwalk viruses from 2 liters of Tokyo Bay water in winter and infectious enteroviruses from 2 liters of recreational coastal seawater in summer were detected by using this viral concentration method.

Development of a virus concentration method and its application to detection of enterovirus and norwalk virus from coastal seawater

We developed a new procedure for concentration of enteric viruses from water using a negatively charged membrane. Rinsing the membrane with 0.5 mM H(2)SO(4) (pH 3.0) in order to elute cations prior to viral elution with 1 mM NaOH (pH 10.5) promoted poliovirus recovery yields from 33 to 95% when applied to pure water and 38 to 89% when applied to natural seawater from Tokyo Bay, Japan, respectively. This method showed average recovery yields of spiked poliovirus of 62% (n = 8) from 1 liter of artificial seawater. This method showed higher recovery yields (>61%) than that of the conventional method using positively charged membrane (6%) when applied to seawater. This method is also free from beef extract elution, which has an inhibitory effect in the subsequent viral genome detection by reverse transcription-PCR. Naturally occurring Norwalk viruses from 2 liters of Tokyo Bay water in winter and infectious enteroviruses from 2 liters of recreational coastal seawater in summer were detected by using this viral concentration method.

Development of a molecular method to identify hepatitis E virus in water

Hepatitis E virus (HEV) causes an infectious form of hepatitis associated with contaminated water. By analyzing the sequence of several HEV isolates, a reverse transcription-polymerase chain reaction method was developed and optimized that should be able to identify all of the known HEV strains. When tested under laboratory conditions, this method was able to detect low levels of five diverse HEV variants. In addition, internal controls were constructed so that any PCR inhibition could be detected. Finally, virus-spiked environmental water samples were analyzed successfully with these assays.

A review of hepatitis E virus

Hepatitis E virus (HEV) is a major cause of outbreaks and sporadic cases of viral hepatitis in tropical and subtropical countries but is infrequent in industrialized countries. The virus is transmitted by the fecal-oral route with fecally contaminated drinking water being the usual vehicle. Hepatitis resulting from HEV infection is a moderately severe jaundice that is self-limiting in most patients. Young adults, 15 to 30 years of age, are the main targets of infection, and the overall death rate is 0.5 to 3.0%. However, the death rate during pregnancy approaches 15 to 25%. Death of the mother and fetus, abortion, premature delivery, or death of a live-born baby soon after birth are common complications of hepatitis E infection during pregnancy. Hepatitis E virus is found in both wild and domestic animals; thus, HEV is a zoonotic virus. The viruses isolated from swine in the United States or Taiwan are closely related to human HEV found in those areas. The close genetic relationship of the swine and human virus suggests that swine may be a reservoir of HEV. In areas where swine are raised, swine manure could be a source of HEV contamination of irrigation water or coastal waters with concomitant contamination of produce or shellfish. Increasing globalization of food markets by industrialized countries has the potential of introducing HEV into new areas of the world. The purpose of this review is to cover certain aspects of hepatitis E including the causative agent, the disease, diagnosis, viral detection, viral transmission, epidemiology, populations targeted by HEV, and the role of animals as potential vectors of the virus.

Concentration and detection of caliciviruses in water samples by reverse transcription-PCR

Human caliciviruses (HuCVs) cause waterborne outbreaks of gastroenteritis. Standard indicators of a safe water supply do not adequately predict contamination of water by viruses, including HuCVs. We developed a method to concentrate and detect HuCVs in water samples by using a cultivable primate calicivirus (Pan-1) as a model. Viable Pan-1 was seeded in different types of water and then filtered with a 1MDS filter, eluted with beef extract (BE), and reconcentrated by polyethylene glycol (PEG) precipitation. The viruses in the final samples were tested by plaque assay or by reverse transcription (RT)-PCR following extraction of the RNA with Trizol. Pan-1 was more sensitive to high-pH treatment than poliovirus was; a pH 9.0 BE solution was found to recover 35% more viable Pan-1 than a pH 9.5 BE solution recovered. Pan-1 was recovered from small volumes of deionized, finished, ground, and surface waters at efficiencies of 94, 73, 67, and 64%, respectively, when samples were assayed after elution without further concentration. When larger volumes of water (up to 40 liters) were tested after elution and concentration with PEG, 38, 19, and 14% of the seeded Pan-1 were recovered from finished, ground, and surface waters, respectively. The limit of detection of Pan-1 by RT-PCR was estimated to be 0.75 to 1.5 PFU in 40 liters of finished water. This method may be adapted for monitoring HuCVs in drinking water and other types of water for public health safety.

Hepatitis E

Hepatitis E, previously known as enterically transmitted non-A, non-B hepatitis, is an infectious viral disease with clinical and morphologic features of acute hepatitis. Its causative agent, hepatitis E virus, consists of small, 32- to 34-nm diameter, icosahedral, nonenveloped particles with a single-stranded, positive-sense, 7.5-kb RNA. The virus has two main geographically distinct strains, Asian and Mexican; recently, novel isolates from nonendemic areas and a genetically related swine HEV have been described. HEV is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in the Indian subcontinent, southeast and central Asia, the Middle East, parts of Africa, and Mexico. The virus is excreted in feces and is transmitted predominantly by fecal-oral route, usually through contaminated water. Person-to-person transmission is uncommon. Clinical attack rates are the highest among young adults. Recent evidence suggests that humans with subclinical HEV infection and animals may represent reservoirs of HEV; however, further data are needed. Diagnosis of hepatitis E is usually made by detection of specific IgM antibody, which disappears rapidly over a few months; IgG anti-HEV persists for at least a few years. Clinical illness is similar to other forms of acute viral hepatitis except in pregnant women, in whom illness is particularly severe with a high mortality rate. Subclinical and unapparent infections may occur; however, chronic infection is unknown. No specific treatment is yet available. Use of clean drinking water and proper sanitation is currently the most effective method of prevention. Passive immunization has not been proved to be effective, and recombinant vaccines for travelers to disease-endemic areas and for pregnant women currently are being developed.

Detection of small round structured viruses in artificially contaminated water using filter adsorption and reverse transcription polymerase chain reaction

The small round structured viruses (SRSV) are common causes of gastroenteritis worldwide. Fecally contaminated water is an important vehicle for transmission, but detection of SRSV in environmental samples has been hampered by the lack of sensitive detection methods. The present work describes the detection of SRSV in artificially contaminated deionized water and raw drinking water. SRSV-containing fecal extracts were added to water and virus was recovered by filter adsorption-elution, followed by flocculation. RNA was extracted and SRSV were detected by the use of reverse transcription polymerase chain reaction. The sensitivity of the method corresponded to a positive SRSV detection in 500 ml deionized water with an estimated concentration of 0.5-5 virus particles per ml.

HAV and HEV infection in hospitalised hepatitis patients in Alexandria, Egypt

A total of 202 serum and stool samples from acute hepatitis patients attending the Fever Hospital of Alexandria, Egypt, have been studied to reveal markers of hepatitis virus infection. Anti-HAV IgM were detected in 21 out of 202 sera (10.4%), whereas 201 sera (99.5%) had anti-HAV IgG. The first age attack was in the class-age 0-9 years with 64.7% of anti-HAV IgM positive sera. Among 202 patients, anti-hepatitis E IgG (sample/over cut off > 1.0) was identified in 90 patients (44.5%). The anti-HEV seropositivity ranged from 17.6% to 60.0% in the different age groups, with the highest level in the class-age 20 29 years. Anti-hepatitis E IgM were identified in 49 patients with the first age attack in the class-age 10-19 years (39.4%). HAV RNA was identified by nested PCR in 7 samples out of 15, whereas HEV RNA was present in 4 out of 75 stool samples. Direct DNA sequence of the latter PCR products confirmed the presence of the HEV genome; comparison of the sequences of the isolates from Egypt with those in data banks revealed the highest homology to the Burma strain. Our data confirm that HAV and HEV are common causes of acute sporadic hepatitis in Alexandria but with different peak age positivity. Occasionally, but not infrequently, dual infections (HAV-HEV and HEV-enteric viruses) were also found. The risk analysis indicates that patients living in rural areas are exposed to a higher risk of hepatitis E infection compared to the urban population, whereas the presence of anti-HEV IgG was significantly associated with consumption of common village water and use of indoor dry pit and oral therapy for schistosomiasis.

Hepatitis E virus -- an update

Hepatitis E virus (HEV) is the principal cause of enterically-transmitted, non-A, non-B hepatitis and has been associated with excess mortality in pregnant women infected during epidemics. Molecular cloning of the viral genome led to the development of diagnostic tests, including enzyme immunoassays for antibody and RT-PCR for viral RNA. Candidate vaccines have not yet reached clinical trials. The virus resembles caliciviruses, with a positive sense RNA genome encoding three open reading frames. The geographical distribution of the virus, which may infect domestic animals as well as humans, may be wider than thought originally.

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.

Immunomagnetic capture PCR for rapid concentration and detection of hepatitis A virus from environmental samples

We studied the concentration of hepatitis A virus (HAV) from environmental samples by membrane filter-based urea-arginine phosphate buffer and its detection by using immunomagnetic capture (IC) reverse transcription (RT)-PCR (IC PCR). Magnetic beads coated with anti-HAV rabbit antibodies were used for enrichment and concentration of HAV from environmental samples. IC PCR is sensitive enough to detect as few as 0.04 PFU of cell culture-adapted HAV in inoculated water and sewage samples. IC PCR is specific and does not yield positive reactions with poliovirus 1, HAV RNA, or selected bacteriophages. IC concentrates viruses suspended in small volumes to microliter volumes that can be used directly in RT-PCR. IC concentration of viruses from sewage samples without concentration of inhibitory substances is important for successful RT-PCR detection. In a field trial, 2 of 18 raw sewage samples tested by IC PCR were positive for HAV.

Quantification of poliovirus in seawater and sewage by competitive reverse transcriptase - polymerase chain reaction

Reverse transcriptase - polymerase chain reaction (RT-PCR) has been used extensively to detect enteric viruses in environmental samples. Advantages of RT-PCR include its high detection sensitivity and rapid turn-around time. However, unlike traditional cell culture, RT-PCR has not provided quantitation and infectivity information. In this study, we have developed a quantitative RT-PCR method that can be used to determine the amount of poliovirus RNA in environmental samples. An RNA internal standard for poliovirus RT-PCR was designed and obtained through genetic engineering. Serial dilutions of RNA internal standard templates were amplified with a 5 prime -carboxyfluorescein-labeled poliovirus downstream primer and a nonlabeled poliovirus upstream primer in the RT-PCR. The fluorescent light intensity of labeled RT-PCR products was quantified using an ABI DNA sequencer with GeneScan software. The internal standard was coamplified with poliovirus in the RT-PCR, allowing for enumeration of the poliovirus RNA present in the seawater and sewage samples. This method, using a cloned internal standard and specified primers in the PCR, may be applied to quantify other microorganisms in environmental samples. Although quantitative RT-PCR has begun to be used more extensively for detecting pathogens in clinical samples, the complex nature of many environmental samples has limited the sample range of the effectiveness of quantitative RT-PCR.Key words: quantitative RT-PCR, poliovirus, sewage, seawater.

Three-step isolation method for sensitive detection of enterovirus, rotavirus, hepatitis A virus, and small round structured viruses in water samples

Control of drinking or bathing water quality in respect to viral contamination remains an unsolved problem. A highly sensitive isolation protocol was developed for concentration and detection of different enteric viruses from water samples. The three-step isolation procedure combines filtration with a positively charged nylon membrane, ultrafiltration and clean-up of the viral RNA with a silica based membrane. Detection of the viral RNA is accomplished by reverse-transcription polymerase chain reaction (RT-PCR). Detection limits were determined to be one 50% tissue culture infective dose (TCID50) of seeded coxsackievirus B2 or hepatitis A Virus per litre of tap water by RT-PCR compared to two orders of magnitude lower sensitivity for culture in the case of coxsackievirus B2. The isolation procedure is highly sensitive, easy to perform and allows the detection of different human pathogenic virus groups in one water sample. The application of the isolation procedure to six river water samples and subsequent detection with nested or semi-nested PCR revealed enterovirus in 6/6 (100%), rotavirus in 6/6 (100%), hepatitis A virus in 0/6 (0%), small round structured virus genotype I in 6/6 (100%) and small round structured virus genotype II in 2/6 (33%) of the samples. These findings suggest that first, we have developed a very sensitive detection procedure and second, that river water in Switzerland-where most of the wastewater is handled by sewage treatment plants-shows a high contamination rate with enteric viruses.

Environmental biotechnology in India: prospects and case studies

The emergence and acceptance of the concept of sustainable development warrants that the scope of environmental biotechnology be enlarged to address issues like environmental monitoring, restoration of environmental quality, resource/residue/waste-recovery/utilization/treatment, and substitution of the non-renewable resource base with renewable resources. This paper delineates the current and prospective applications in these sub-areas of environmental biotechnology, and documents case studies on environmental monitoring (enteric viruses), restoration of environmental quality (oil spill remediation), resource recovery (hydrocarbon recovery from oily sludges, biosurfactants from distillery spentwash, desulphurization of coal & sour gases), and substitution of non-renewable resources with renewables (conversion of lignocellulisics into value added chemicals).

Hepatitis E

Hepatitis E has a world-wide distribution and causes substantial morbidity and mortality in some developing countries, particularly among pregnant women. Hepatitis E virus (HEV) has recently been cloned and sequenced, and new diagnostic tests have been developed. These tests have been used to begin to characterize the natural history and epidemiological features of HEV infection. Experimental vaccines have also been developed that offer the potential to prevent hepatitis E. However, much remains to be learned about HEV, including the mechanisms of transmission, the reservoir(s) of the virus, and the natural history of protective immunity in order to develop effective strategies to prevent this disease.