Hepatitis E Seroprevalence in Europe: A Meta-Analysis

A cross-sectional study among Polish hunters: seroprevalence of hepatitis E and the analysis of factors contributing to HEV infections

Hepatitis E virus (HEV) is known as zoonotic agent. The main reservoirs of HEV in Europe are pigs, wild boars, and deer. Hunting activity is considered to be a risk factor for HEV infection. We conducted a cross-sectional study among 1021 Polish hunters. To understand socio-demographic characteristics of this population and to gather information on potential exposures, all participants completed a questionnaire. Commercial immunoassays were employed to estimate seroprevalence anti-HEV. Samples with confirmed positive result of anti-HEV IgM were examined for HEV RNA. Anti-HEV IgG were identified in 227 people, 22.2% of the studied group. Seroprevalence among the studied hunters was associated with age ≥65 [adjusted prevalence ratio (aPR) 1.6, p = 0.037), living in a house (aPR 1.54, p = 0.013), professional contact with farm animals (aPR 1.09, p = 0.01), and consumption of stewed offal (aPR 1.61, p = 0.00). Washing hands after disembowelment was linked to lower seroprevalence (aPR 0.53; p = 0.00). Lower prevalence of anti-HEV IgG among hunters living in cities was associated with age: 35–49 (aPR 0.52, p = 0.011) and 50–64 (aPR 0.93, p = 0.58), living in a house (aPR 1.58, p = 0.002) and owning a cat (aPR 0.58, p = 0.042). Among hunters living in rural areas, seropositivity was associated with contact with farm animals (aPR 1.66, p = 0.013) and consumption of stewed offal (aPR 1.81; p = 0.001). Contrary to initial assumptions, it was concluded that hunting was of significantly lesser importance than other factors. Due to the high level of HEV seroprevalence identified, we recommend conducting a large-scale study in the general population of Poland.

The Enigma of Hepatitis E Virus

Globally, hepatitis E virus (HEV) is the most common cause of acute viral hepatitis. HEV is endemic in many developing countries, yet it is far more common in industrialized, nonendemic countries than previously recognized. Nonetheless, HEV remains poorly characterized and is frequently unidentified or misdiagnosed by clinicians. Manifestation of disease, source of infection, and route of transmission vary by HEV genotype and epidemiology in endemic and nonendemic settings worldwide. HEV infection can be acute or chronic, further complicating the presentation, diagnosis, prognosis, and natural history of disease. However, accurate identification and diagnosis of HEV has important implications for patient management, disease control, prevention efforts, and characterization of mechanisms of transmission and epidemiology. Acute HEV infection is rarely diagnosed in industrialized, nonendemic countries; however, recent seroprevalence data collected using modern, highly sensitive testing assays demonstrate a surprisingly high prevalence of anti-HEV antibodies in these settings, suggesting common subclinical or unrecognized infection. These data suggest widespread underestimation of the global burden, population seroprevalence, and importance of HEV infection. Enhanced capacity for disease recognition, accurate diagnosis, and clinical awareness are critical to improving the management and reducing the burden of HEV infection worldwide.

Review article: hepatitis E-a concise review of virology, epidemiology, clinical presentation and therapy

BACKGROUND

Hepatitis E virus (HEV) is a leading cause of acute icteric hepatitis and acute liver failure in the developing world. During the last decade, there has been increasing recognition of autochthonous (locally acquired) HEV infection in developed countries. Chronic HEV infection is now recognised, and in transplant recipients this may lead to cirrhosis and organ failure.

AIM

To detail current understanding of the molecular biology of HEV, diagnostic and therapeutic strategies and propose future directions for basic science and clinical research.

METHODS

PubMed was searched for English language articles using the key words "hepatitis E", "viral hepatitis", "autochthonous infection", "antiviral therapy", "liver transplantation", "acute", "chronic", "HEV", "genotype", "transmission" "food-borne", "transfusion". Additional relevant publications were identified from article reference lists.

RESULTS

There has been increasing recognition of autochthonous HEV infection in Western countries, mainly associated with genotype 3. Chronic HEV infection has been recognised since 2008, and in transplant recipients this may lead to cirrhosis and organ failure. Modes of transmission include food-borne transmission, transfusion of blood products and solid organ transplantation. Ribavirin therapy is used to treat patients with chronic HEV infection, but new therapies are required as there have been reports of treatment failure with ribavirin.

CONCLUSIONS

Autochthonous HEV infection is a clinical issue with increasing burden. Future work should focus on increasing awareness of HEV infection in the developed world, emphasising the need for clinicians to have a low threshold for HEV testing, particularly in immunosuppressed patients. Patients at potential risk of chronic HEV infection must also be educated and given advice regarding prevention of infection.

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.

Asymptomatic acute hepatitis E in a female patient with ulcerative colitis

We present a 60-year-old female patient with asymptomatic acute hepatitis E that was fortuitously detected during the course of ulcerative colitis (UC). She was admitted to hospital on October 30, 2015. Endoscopy and histological examination of the colon showed typical findings of UC. All parameters of liver function tests were normal on this date. Combination therapy with oral prednisolone and mesalazine was started and intravenous administration of infliximab once every 8 weeks was added later. Her symptoms gradually improved after these treatments, and she was discharged on February 7, 2016. In a periodic check-up on July 7, 2016, high levels of serum transaminases were detected in liver function tests. Although drug-induced liver injury was first suspected, anti-hepatitis E virus (HEV) immunoglobulin A was positive. The genotype and subgenotype of this HEV are 3 and 3a, respectively, although the infectious route of the HEV was unclear. Within 2 weeks after the onset of acute liver injury, the HEV viremia disappeared and her liver function tests improved. Examination of serum anti-HEV immunoglobulin A should be added at the time of abnormal liver function tests in patients with UC receiving immunosuppressive and biological drugs.

Hepatitis E Virus and the Liver: Clinical Settings and Liver Pathology

Infection with hepatitis E virus (HEV) is a leading cause of acute hepatitis worldwide, now increasingly recognized also in nonendemic regions. Clinical manifestation of hepatitis E includes mostly asymptomatic/subclinical presentations or acute, self-limiting hepatitis, but also potentially fatal liver failure or chronic hepatitis in immunocompromised individuals. Accordingly, hepatitis E histolpathologic patterns range from an unremarkable histology over acute (cholestatic) hepatitis with variable degree of necrosis to chronic hepatitis with fibrosis. Awareness of hepatitis E and its differential diagnoses, knowledge of its clinico-pathologic manifestations and familiarity with its diagnostic tools will enable clinicians and pathologists to competently make this diagnosis.

Hepatitis E virus IgG seroprevalence in HIV patients and blood donors, west-central Poland

OBJECTIVE

To assess hepatitis E virus (HEV) seroprevalence in HIV patients and blood donors from one region in Poland.

METHODS

A group of 490 persons (244 HIV patients and 246 blood donors) aged 18-55 years were examined using the anti-HEV IgG assay (Wantai Biological Pharmacy Enterprise, Beijing, China). An analysis of the association between certain factors and the presence of this HEV exposure marker was conducted in both groups.

RESULTS

An HEV seropositivity rate of 50.2% was found. There was no difference in HEV seroprevalence between blood donors (49.6%, 122/246) and HIV patients (50.8%, 124/244) (p=0.569). The anti-HEV IgG positivity rate increased with age as follows: 36.2% (59/163) in persons aged 18-30 years, 52.0% (92/177) in individuals aged 31-40 years and 63.3% (95/150) in those aged 41-55 years. HEV infection occurred in 56.4% (31/55) of people who had never travelled abroad.

CONCLUSIONS

Wielkopolska Region in west-central Poland is an area hyperendemic for HEV infection. In this part of Poland, the exposure of HIV-positive persons to this virus is not greater than that of healthy blood donors.

The added value of hepatitis E diagnostics in determining causes of hepatitis in routine diagnostic settings in the Netherlands

OBJECTIVES

Hepatitis E virus (HEV) genotype 3 is endemic in Europe and an underdiagnosed and emerging (public) health issue. In recent years commercial enzyme immunoassays (EIAs) that detect antibodies to HEV more adequately, became available. We investigated the added value of this HEV serology in the diagnostic work flow to detect viral causes of recent hepatitis.

METHODS

During a 2-year period (May 2013 to May 2015), HEV serology was added to the hepatitis work flow, consisting of serological detection of hepatitis viruses A, B and C (HAV, HBV, HCV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Samples positive for HEV IgM were also analysed using PCR to detect HEV RNA. If positive, HEV sequencing was performed for genotyping purposes.

RESULTS

In 235 out of 2521 patients (9.3%), a viral cause for hepatitis was found. Recent HAV, HBV, HCV, EBV or CMV infections were serologically diagnosed in 3, 34, 10, 69 and 42 patients, respectively. Seventy-eight patients (3.1%) had a recent HEV infection. In 49 of them, sufficient HEV RNA was present for genotyping. All patients were infected with HEV genotype 3.

CONCLUSIONS

In our region, an HEV infection is the most frequently diagnosed viral cause for recent hepatitis. These results indicate that, in a country where HEV is endemic, serological HEV diagnostics should be added to the standard work-up for viral hepatitis.

Rural habitat as risk factor for hepatitis E virus seroconversion in HIV-infected patients: A prospective longitudinal study

Our objective was to determine the incidence and clinical manifestations of acute hepatitis E virus (HEV) in HIV-infected patients. A prospective longitudinal study including HIV-infected HEV-seronegative patients was conducted; HEV seroconversion (to IgG and/or IgM) was the main outcome variable. All patients were tested for HEV antibodies every 3-6 months. For patients who developed HEV seroconversion, a data collection protocol was followed to identify associated clinical manifestations and analytical alterations. A total of 627 patients (89.9%) were followed during a median of 11.96 months (IQR: 8.52-14.52 months) and formed the study population. Forty-one patients developed detectable anti-HEV antibodies (7.2 cases per 100 patients/year). Our study found a high incidence of HEV in HIV-infected patients in southern Spain strongly associated with a rural habitat.

Seroprevalence of hepatitis E virus in Lithuanian domestic pigs and wildlife

Hepatitis E is an important public health concern disease that causes acute hepatitis in humans with different hepatitis E virus strains reported among domestic and wild animals. In Lithuania, seroprevalence studies on animals considered to be possible virus reservoirs, particularly in wildlife species, had never been investigated before. In order to assess the actual distribution of the virus in the domestic pig and wildlife species, serum samples originating from different geographic areas of Lithuania were tested for the presence of antibodies to the virus using enzyme-linked immunosorbent assay. The study results proved that hepatitis E virus infection is prevalent among domestic pigs, wild boar, moose, and roe deer in Lithuania, with the overall prevalence of IgG antibodies against hepatitis E virus being 43.75%, 57.05%, 11.76%, and 1.20%, respectively. Significantly higher (P< 0.01) seroprevalence values of 53.66% and 80% were observed in weaned pigs and adult wild boar. Herds with 15 001–30 000 pigs were 2.4 times more likely (P< 0.01) to test positive for hepatitis E virus antibodies (70.18%), than herds with ≤ 500 pigs (21.11%). The differences in seroprevalence rates between domestic pigs (from 25 to 66.67%) and wild boar (from 42.86 to 73.33% ) in all 10 counties were not significant (P> 0.05). Estimated low seroprevalence rate in moose, roe deer and absence of antibodies in red deer suggest that such wildlife species are accidental hosts of hepatitis E virus or at least hepatitis E virus is not present in Lithuanian cervides.

Hepatitis E virus seroprevalence among the general population in a livestock-dense area in the Netherlands: a cross-sectional population-based serological survey

Background

Recent serological studies indicate that hepatitis E virus (HEV) is endemic in industrialised countries. The increasing trend in the number of autochthonous cases of HEV genotype 3 in Western European countries, stresses the importance to get insight in the exact routes of exposure. Pigs are the main animal reservoir, and zoonotic food-borne transmission of HEV is proven. However, infected pigs can excrete large amounts of virus via their faeces enabling environmental transmission of HEV to humans. This might pose a risk for of neighbouring residents of livestock farming.

Methods

Within a large study on the health of people living in the vicinity of livestock farming we performed a cross-sectional population-based serological survey among 2,494 non-farming adults from the general population in a livestock-dense area in the south of the Netherlands. Participants completed risk factor questionnaires and blood samples of 2,422 subjects (median age 58 years, range 20–72) were tested for anti-HEV IgG using an enzyme immune assay (Wantai). The aim of this study was to determine the HEV seroprevalence and to assess whether seropositivity in adults was associated with living in the vicinity of pig farms.

Results

The average seroprevalence of HEV was 28.7% (95% CI: 26.9–30.5). Determinants associated with an increased risk for HEV seropositivity were male gender and low level of education. There was a clear trend of increasing prevalence with increasing age (Chi-square test for linear trend, X² = 83.1; p < 0.001). A high number of pigs within 1,000 m of the residential address was not a risk factor for seropositivity.

Conclusions

This study confirmed the high HEV seroprevalence (29%) in the general population of the Netherlands, but presence of antibodies was not associated with residential proximity to pig farms. The prevalence increased with age from 10% in adolescents to 33% among those aged 50 and above, supporting the assumption of a cumulative lifetime exposure to HEV in the Netherlands as well as a higher infection pressure in the past. Our findings cannot refute the assumption that transmission is primarily food-borne.

Hepatitis E Virus in Industrialized Countries: The Silent Threat

Hepatitis E virus (HEV) is the main cause of acute viral hepatitis worldwide. Its presence in developing countries has been documented for decades. Developed countries were supposed to be virus-free and initially only imported cases were detected in those areas. However, sporadic and autochthonous cases of HEV infection have been identified and studies reveal that the virus is worldwide spread. Chronic hepatitis and multiple extrahepatic manifestations have also been associated with HEV. We review the data from European countries, where human, animal, and environmental data have been collected since the 90s. In Europe, autochthonous HEV strains were first detected in the late 90s and early 2000s. Since then, serological data have shown that the virus infects quite frequently the European population and that some species, such as pigs, wild boars, and deer, are reservoirs. HEV strains can be isolated from environmental samples and reach the food chain, as shown by the detection of the virus in mussels and in contaminated pork products as sausages or meat. All these data highlight the need of studies directed to control the sources of HEV to protect immunocompromised individuals that seem the weakest link of the HEV epidemiology in industrialized regions.

Retrospective Study Evaluating Seroprevalence of Hepatitis E Virus in Blood Donors and in Swine Veterinarians in Italy (2004)

Hepatitis E is an emerging viral disease in developed countries, with sporadic cases occasionally linked to the consumption of raw or undercooked pork, wild boar or deer meat. Cases due to transfusion or transplantation have also been reported. In developed countries, hepatitis E is considered a zoonosis and pig is the main reservoir. In the last few years, several studies conducted in Europe reported variable seroprevalence rates among the general population, ranging between 0.26% and 52.5%. A higher seroprevalence was described among workers who come in contact with pigs. The aim of this retrospective study was to evaluate the seroprevalence of anti-HEV IgG and IgM antibodies in blood donors (170) and in pig veterinarians (83). Archival sera were collected in Italy in 2004. The observed seroprevalence was 9.64% and 8.82% in veterinarians and blood donors, respectively. Overall, only three sera from blood donors were positive for IgM, but no HEV-RNA was detected.

Acute Hepatitis E: Two Sides of the Same Coin

The relevance of acute hepatitis E virus (HEV) infections has been underestimated for a long time. In the past, HEV infection had been interpreted falsely as a disease limited to the tropics until the relevance of autochthonous HEV infections in the Western world became overt. Due to increased awareness, the incidence of diagnosed autochthonous HEV infections (predominantly genotype 3) in industrialized countries has risen within the last decade. The main source of infections in industrialized countries seems to be infected swine meat, while infections with the tropical HEV genotypes 1 and 2 usually are mainly transmitted fecal-orally by contaminated drinking water. In the vast majority of healthy individuals, acute HEV infection is either clinically silent or takes a benign self-limited course. In patients who develop a symptomatic HEV infection, a short prodromal phase with unspecific symptoms is followed by liver specific symptoms like jaundice, itching, uncoloured stool and darkened urine. Importantly, tropical HEV infections may lead to acute liver failure, especially in pregnant women, while autochthonous HEV infections may lead to acute-on-chronic liver failure in patients with underlying liver diseases. Immunosuppressed individuals, such as transplant recipients or human immunodeficiency virus (HIV)-infected patients, are at risk for developing chronic hepatitis E, which may lead to liver fibrosis and cirrhosis in the long term. Importantly, specific treatment options for hepatitis E are not approved by the regulation authorities, but off-label ribavirin treatment seems to be effective in the treatment of chronic HEV-infection and may reduce the disease severity in patients suffering from acute liver failure.

Hepatitis E virus: Emerging from the shadows in developed countries

Following the discovery of HEV in the 1980s, it became apparent that HEV is endemic in a number of developing countries in Asia, Africa and Mexico. In these geographical settings HEV is spread oral faecally by HEV genotypes (gt) 1 and 2, which are obligate human pathogens. Infection occurs oro-faecally, often as a result in the breakdown of fragile sanitary infrastructure allowing drinking water supplies to become contaminated with human sewage. Hepatitis E usually causes a self-limiting hepatitis in young adults with sporadic cases and occasional dramatic outbreaks involving hundreds or thousands of cases. Clinically the illness is indistinguishable from hepatitis A, except in pregnant women where the mortality is 20-25%. Death occurs in the third trimester from fulminant hepatic failure and obstetric complications such as eclampsia, with very high associated foetal loss. For the best part of 20 years hepatitis E was considered as an imported disease in developed countries, and was only seen in travellers returning from endemic developing countries. We got this very badly wrong: HEV gt3 was 'hiding in the shadows' in humans, pigs, and other animals.