Prevalence and genotyping of hepatitis E virus in swine population in Korea between 1995 and 2004: a retrospective study

Hepatitis E Virus in the Role of an Emerging Food-Borne Pathogen

Viral hepatitis E represents an important global health problem caused by the hepatitis E virus (HEV). Cases of HEV infection are increasingly associated with food-borne transmissions after the consumption of raw or undercooked food products from infected animals in high-income regions. Although most cases of infection are asymptomatic, severe courses of infection have been reported in specific groups of people, predominantly among pregnant women and immunocompromised patients. The viral nucleic acid of HEV is increasingly being reported in food-producing animals and different products of an animal origin. Even though the incubation period for HEV infection is long, several direct epidemiological links between human cases and the consumption of HEV-contaminated meat and meat products have been described. In this article, we review the current knowledge on human HEV infections, HEV in different food-producing animals and products of an animal origin, as well as the accumulation and resistance to HEV in farm and slaughterhouse environments. We also provide preventive measures to help eliminate HEV from animals, the human population, and the environment.

Hepatitis E Virus in Livestock-Update on Its Epidemiology and Risk of Infection to Humans

Hepatitis E virus (HEV) is a public health problem worldwide and an important food pathogen known for its zoonotic potential. Increasing numbers of infection cases with human HEV are caused by the zoonotic transmission of genotypes 3 and 4, mainly by consuming contaminated, undercooked or raw porcine meat. Pigs are the main reservoir of HEV. However, it should be noted that other animal species, such as cattle, sheep, goats, and rabbits, may also be a source of infection for humans. Due to the detection of HEV RNA in the milk and tissues of cattle, the consumption of infected uncooked milk and meat or offal from these species also poses a potential risk of zoonotic HEV infections. Poultry infected by avian HEV may also develop symptomatic disease, although avian HEV is not considered a zoonotic pathogen. HEV infection has a worldwide distribution with different prevalence rates depending on the affected animal species, sampling region, or breeding system.

Persistence of hepatitis E virus in the liver of non-viremic naturally infected wild boar

Hepatitis E virus (HEV) is an emerging zoonotic pathogen with pigs and wild boar serving as reservoirs for human infection through direct contact with infected animals or the consumption of raw or undercooked pork products. The liver is considered the main target site of HEV replication in swine and an important organ in the pathogenesis of the disease. The aim of this study was to characterize the target liver cells for HEV entry in naturally infected wild boar and to evaluate the type and severity of the pathological changes in order to reach a better understanding of the hepatic pathogenic mechanisms involved in hepatitis E. In total, 58 livers from hunted wild boar were histopathologically evaluated. The presence of specific HEV antibodies in serum was determined by indirect ELISA. Immunohistochemistry was used for the detection of HEV antigen and Real time RT-PCR to detect HEV RNA in liver and serum. HEV seroprevalence in these animals was of 5.197% (CI_95%: 1.77–14.14). By Real time RT-PCR, HEV was detected in the liver tissue of four wild boar (6.8%; CI_95%: 2.7–16.4) and only one animal was also positive in serum (1.7%; CI_95%: 0.3–9.1). The non-viremic animals naturally infected with HEV presented evidence of liver infection, mainly in Kupffer cells and liver sinusoidal endothelial cells, without apparent associated hepatitis lesions. This study supports the hypothesis that low viral titers may persist in the liver of non-viremic individuals, giving thus the possibility of consumption of contaminated liver of animals diagnosed as HEV-negative in serum. Further immunopathogenic studies are necessary to elucidate the mechanisms responsible for this process and to evaluate the protocols of HEV diagnosis in animals destined for human consumption.

From the epidemiology of hepatitis E virus (HEV) within the swine reservoir to public health risk mitigation strategies: a comprehensive review

Hepatitis E virus (HEV) is the causative agent of hepatitis E in humans, an emerging zoonosis mainly transmitted via food in developed countries and for which domestic pigs are recognised as the main reservoir. It therefore appears important to understand the features and drivers of HEV infection dynamics on pig farms in order to implement HEV surveillance programmes and to assess and manage public health risks. The authors have reviewed the international scientific literature on the epidemiological characteristics of HEV in swine populations. Although prevalence estimates differed greatly from one study to another, all consistently reported high variability between farms, suggesting the existence of multifactorial conditions related to infection and within-farm transmission of the virus. Longitudinal studies and experimental trials have provided estimates of epidemiological parameters governing the transmission process (e.g. age at infection, transmission parameters, shedding period duration or lag time before the onset of an immune response). Farming practices, passive immunity and co-infection with immunosuppressive agents were identified as the main factors influencing HEV infection dynamics, but further investigations are needed to clarify the different HEV infection patterns observed in pig herds as well as HEV transmission between farms. Relevant surveillance programmes and control measures from farm to fork also have to be fostered to reduce the prevalence of contaminated pork products entering the food chain.

Risk factors associated with the presence of hepatitis E virus in livers and seroprevalence in slaughter-age pigs: a retrospective study of 90 swine farms in France

The frequency of sporadic cases of hepatitis E in humans in developed countries has increased in recent years. The consumption of raw or undercooked pig liver-based products has been identified as an important source of human infection. The question of possible massive human exposure to this zoonotic agent has been raised by the high prevalence of hepatitis E virus (HEV) in swine herds. However, little is known about the epidemiology of HEV on pig farms. A retrospective study, based on a previous prevalence study of 185 farms, was conducted on 90 farms located in Western France, randomly selected from this database, to identify factors associated with the presence of HEV in pig livers and HEV seroprevalence in slaughter-age pigs. At least one HEV RNA-positive liver was found in 30% of the sampled farms while seroprevalence in slaughter-age pigs at the farm level reached almost 75%. Different factors were associated with the two conditions. The risk of having HEV-positive livers was increased by early slaughter, genetic background, lack of hygiene measures and surface origin of drinking water. High HEV seroprevalence was associated with mingling practices at the nursery stage and hygiene conditions. These results can be used to determine on-farm measures to reduce within-farm HEV spread and infection of slaughter-age pigs.

Current status of hepatitis e virus infection in Korea

Hepatitis E virus (HEV) is an emerging pathogen associated with acute viral hepatitis, and HEV is becoming increasingly recognized. Approximately 2% of acute viral hepatitis is caused by HEV, and 18 cases of hepatitis E have been reported in Korea. Of these cases, only two have involved a history of travel from India, which suggests that they were imported cases. The remaining reported cases include a sporadic case of acute hepatitis E with genotype 4 HEV isolates and identification of the full genome sequence, as well as another case of genotype 4 HEV hepatitis that developed after ingestion of the raw bile juice of a wild bear living on a mountain in southern Korea. Moreover, genotype 3 HEV, which shows close genetic homology with swine HEV in Korea, has been detected in collected human serum samples. Therefore, genotypes 3 and 4 HEV are currently circulating in the Korean community and may be related to zoonotic transmission and food-borne infection. The reported anti-HEV seroprevalence of 17% to 27% in the Korean population suggests that HEV infection has been autochthonously circulating, thereby resulting in subclinical infection in Korea. Given the discrepancies among anti-HEV assays, the diagnosis of hepatitis E should be made with caution using adequate antibody assays, and HEV RNA should be preferably detected from the stool. Further virological characterization and epidemiological study of the virus are warranted.

Widespread distribution of hepatitis E virus in Spanish pig herds

Background

Hepatitis E virus (HEV) infection is a serious health problem in developing countries and is also increasingly reported in industrialized regions. HEV is considered a zoonotic agent and strains isolated from swine and human sources are genetically similar. Thus, HEV is of increasing importance to both public and animal health. The aim of the present study was to evaluate the distribution of HEV in a large population of pigs from herds located in different autonomous regions throughout Spain.

Results

The presence of anti-HEV IgG antibodies was analyzed in 1141 swine serum samples (corresponding to 381 pigs younger than 6 months and 760 pigs older than 6 months) collected from 85 herds. Herds were located in 6 provinces in 4 autonomous regions throughout Spain. At least one pig tested positive for anti-HEV IgG in over 80% of herds. Of individual pigs, 20.4% (233/1141) were positive for anti-HEV IgG, with the prevalence being higher in adult pigs than in those under 6 months (30.2% vs. 15.5%). A subset of serum samples taken at 2- to 5-week intervals showed that seroprevalence dropped between 3 and 11 weeks of age, and then rose significantly by the 15th week. Pigs were also examined for the presence of HEV-RNA by RT-PCR. Of pigs tested for the presence of HEV-RNA 18.8% (64/341) were positive, with at least one pig in almost half of the herds testing positive. HEV-RNA amplicons from several positive pigs were sequenced and all were of genotype 3.

Conclusions

HEV was found to be widely distributed among swine farms across Spain, with the prevalence being highest among animals older than 6 months. These results indicate that HEV infection either is or is likely to become endemic in the Spanish swine population.

Development of duplex RT-PCR-ELISA for the simultaneous detection of hepatitis A virus and hepatitis E virus

This study aimed to develop a specific and sensitive duplex reverse transcription polymerase chain reaction enzyme-linked immunosorbent assay (duplex RT-PCR-ELISA) for hepatitis A virus (HAV) and hepatitis E virus (HEV). Duplex RT-PCR-ELISA could detect and differentiate HAV and HEV with specific probes. When ELISA technique was used to detect probe-bound RT-PCR products, duplex RT-PCR-ELISA could detect as little as 0.1 ng/μL HAV and HEV from clinical samples. Human norovirus, enterovirus, poliovirus, murine norovirus and feline calicivirus were used for the specificity test; all were negative. Therefore duplex RT-PCR-ELISA can be used for the simultaneous detection of HAV and HEV in contaminated fecal samples.

Hepatitis E in high-income countries

PURPOSE OF REVIEW

To discuss recent advances in characterising viral Hepatitis E (HEV) in nonendemic regions, with a special focus on epidemiology in high-income countries, different clinical aspects of the disease, possible zoonotic origin of these cases and the improvement of Hepatitis E diagnosis.

RECENT FINDINGS

In high-income countries, most cases of Hepatitis E are acquired locally and not imported from endemic regions. Different genotypes are involved in indigenous cases than those in endemic regions. Particular population groups, such as transplant recipients, can be persistently infected by hepatitis E and develop chronic diseases. Viral hepatitis E is frequently observed in people in animal care occupations. Indeed, HEV has a large animal reservoir and this emerging disease in developed countries has probably a zoonotic origin.

SUMMARY

Recent studies on viral Hepatitis E have shown that the epidemiology of the disease differs between endemic and nonendemic regions. Several lines of evidence suggest that Hepatitis E is more frequent than was suspected and that it has a possible animal origin. Particular attention must be paid to the possible chronic evolution of various forms of the disease. Surveillance of human cases and animal reservoirs must be developed further.

Zoonotic hepatitis E: animal reservoirs and emerging risks

Hepatitis E virus (HEV) is responsible for enterically-transmitted acute hepatitis in humans with two distinct epidemiological patterns. In endemic regions, large waterborne epidemics with thousands of people affected have been observed, and, in contrast, in non-endemic regions, sporadic cases have been described. Although contaminated water has been well documented as the source of infection in endemic regions, the modes of transmission in non-endemic regions are much less known. HEV is a single-strand, positive-sense RNA virus which is classified in the Hepeviridae family with at least four known main genotypes (1–4) of mammalian HEV and one avian HEV. HEV is unique among the known hepatitis viruses, in which it has an animal reservoir. In contrast to humans, swine and other mammalian animal species infected by HEV generally remain asymptomatic, whereas chickens infected by avian HEV may develop a disease known as Hepatitis-Splenomegaly syndrome. HEV genotypes 1 and 2 are found exclusively in humans while genotypes 3 and 4 are found both in humans and other mammals. Several lines of evidence indicate that, in some cases involving HEV genotypes 3 and 4, animal to human transmissions occur. Furthermore, individuals with direct contact with animals are at higher risk of HEV infection. Cross-species infections with HEV genotypes 3 and 4 have been demonstrated experimentally. However, not all sources of human infections have been identified thus far and in many cases, the origin of HEV infection in humans remains unknown.

Much meat, much malady: changing perceptions of the epidemiology of hepatitis E

Hepatitis E, which is caused by hepatitis E virus (HEV), may now be considered a zoonosis as well as an anthroponosis. Pigs, boars and deer have been identified as reservoirs, and their flesh and entrails--as meat and offal--as vehicles of HEV transmission. Shellfish also act as vehicles. Dietary, gastronomic and culinary preferences influence how extensively HEV conveyed by these vehicles can be inactivated before their ingestion by the host. Another route of infection is paved by HEV that is enterically shed by humans and by live animals into the environment. Although anthroponotic transmission of HEV is primarily environmental, zoonotic transmission may proceed along both foodborne and environmental routes.

Determination of fecal shedding rates and genotypes of swine hepatitis E virus (HEV) in Korea

Hepatitis E virus (HEV) infection induces an acute hepatitis or a subclinical disease in humans. It is known that HEV is a zoonotic agent and pigs are major reservoirs of HEV. This study was conducted to determine the fecal shedding rates of HEV in various age groups of pigs and identify the genotypes of swine HEV prevailing in Korea. A total of 565 fecal samples were collected from suckling piglets, post-weaning pigs, growing pigs, and sows at 12 swine farms. RT-PCR was used to detect the presence of swine HEV in the feces. Every swine farm examined in this study had HEV-infected pigs. The fecal shedding rates of the swine HEV at individual farms were in the range of 2.1-35.4%. The overall fecal shedding rate of HEV in individual pigs was 17.5%. The HEV shedding rates of suckling piglets, post-weaning pigs, growing pigs and sows in their feces were 6.3, 16.3, 38.0 and 9.3%, respectively. When the genotypes of swine HEVs identified in this study were determined, they were all grouped into genotype 3. They were further subdivided into subtype 3a together with human and swine HEVs isolated in the U.S.A.

[Recent etiology and clinical features of acute viral hepatitis in a single center of Korea]

BACKGROUND AND AIMS

The etiology of acute viral hepatitis in Korea has been dynamically changing during the recent years. The aim of this study was to investigate the recent etiology and the clinical features of acute viral hepatitis in a single center of Korea.

METHODS

We performed a retrospective analysis of a prospective cohort of 55 patients who were diagnosed with acute viral hepatitis A to E during the period from May 2005 to August 2006. In addition to the clinically acute manifestations, the confirmatory serological tests were performed for the diagnosis of acute hepatitis A, B, C and E.

RESULTS

The proportion of patients with acute viral hepatitis A, B, C, E and others were 56.4% (n=31), 12.7% (n=7), 18.2% (n=10), 9.1% (n=5) and 3.6% (n=2), respectively. The mean age of the patients with acute hepatitis A, B, C and E were 29.1+/-4.38, 38.7+/-11.72, 45.3+/-17.62 and 32.4+/-6.58 years, respectively. There was no fatal case. All cases of acute hepatitis B and six out of ten cases of acute hepatitis C recovered spontaneously. Four out of the five patients with acute hepatitis E had no history of travel to endemic area.

CONCLUSIONS

The most common etiology of acute viral hepatitis in Korea is hepatitis A virus, and hepatitis C and B virus were the next most common causes. The sporadic cases of acute hepatitis E were not rare, and coinfection of HAV and HEV was observed. A multicenter, prospective study is warranted in the future.

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.

Retrospective serological study on hepatitis E infection in pigs from 1985 to 1997 in Spain

The objective of the present work was to ascertain the date in which hepatitis E virus (HEV) was introduced in the Spanish pig population. For this, a serological retrospective study was carried out using archived sera. A total of 2871 serum samples gathered between 1985 and 1997 and collected in 208 farms of Spain were tested for anti-HEV IgG by an in-house ELISA. Of the 2871 sera analyzed by ELISA, 1390 were positive for anti-HEV antibodies (48.4%, 95% CI: 46.9-49.9%) and that corresponded to 204/208 farms (98%, 95% CI: 96.1-99.9%) having at least one positive pig. Our results show that HEV was present and widespread in Spanish swine farms at least since 1985. Any significant changes in prevalence were detected from 1 year to another and therefore, HEV infection in swine should be considered endemic in Spain.

Serological and molecular evidence of hepatitis E virus in swine in Brazil

Active hepatitis E virus (HEV) infections in two Brazilian swine herds were investigated. In study 1, 26 piglets born to five anti-HEV positive sows were monitored from birth to post-partum week 22. Serum samples were screened for the detection of anti-HEV antibodies and a nested RT-PCR used to examine the HEV genome. Passive transfer of immunity was confirmed. At week 22, 23/26 (88.4%) of the piglets had seroconverted. Genome amplification was achieved in a feces pool from one holding pen and in one serum sample, both from 13-week-old animals. Histology was suggestive of a potential HEV infection. In the second study, 47 piglets born to six anti-HEV-positive sows were monitored after weaning. Seroconversion was determined in eight animals at 6-8 weeks of age. HEV RNA was detected in two pools from a holding pen for 12-16-week-old animals. Brazilian isolates were classified as genotype 3. This is the first molecular evidence of HEV infection in Brazilian pig herds.