Serological evidence of hepatitis E virus infection in pigs and jaundice among pig handlers in Bangladesh

Annual risk of hepatitis E virus infection and seroreversion: Insights from a serological cohort in Sitakunda, Bangladesh

Hepatitis E virus (HEV) is a major cause of acute jaundice in South Asia. Gaps in our understanding of transmission are driven by non-specific symptoms and scarcity of diagnostics, impeding rational control strategies. In this context, serological data can provide important proxy measures of infection. We enrolled a population-representative serological cohort of 2,337 individuals in Sitakunda, Bangladesh. We estimated the annual risks of HEV infection and seroreversion both using serostatus changes between paired serum samples collected 9 months apart, and by fitting catalytic models to the age-stratified cross-sectional seroprevalence. At baseline, 15% (95 CI: 14-17%) of people were seropositive, with seroprevalence highest in the relatively urban south. During the study, 27 individuals seroreverted (annual seroreversion risk: 15%, 95 CI: 10-21%), and 38 seroconverted (annual infection risk: 3%, 95CI: 2-5%). Relying on cross-sectional seroprevalence data alone, and ignoring seroreversion, underestimated the annual infection risk five-fold (0.6%, 95 CrI: 0.5-0.6%). When we accounted for the observed seroreversion in a reversible catalytic model, infection risk was more consistent with measured seroincidence. Our results quantify HEV infection risk in Sitakunda and highlight the importance of accounting for seroreversion when estimating infection incidence from cross-sectional seroprevalence data.

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.

Hepatitis E Virus (HEV) Synopsis: General Aspects and Focus on Bangladesh

HEV is the most common cause of acute hepatitis globally. This review summarizes the latest knowledge on the epidemiology, clinical characteristics, testing, and treatment of HEV infection. We also focused on Bangladesh to highlight the distinct challenges and the possible remedies. In low-income settings, the virus is mainly transmitted between people by fecal contamination of drinking water causing large outbreaks, and sporadic cases. The disease is usually mild and self-limiting acute hepatitis. Still, pregnant women and their offspring in low-income countries are at particular risk for severe disease, with up to 20% maternal mortality. Despite the high burden of the disease, HEV remains a relatively neglected virus, with detection hampered by costly tests and a lack of suitable treatments. Molecular PCR diagnostics, together with ELISA antibody tests, remain the preferred methods for diagnosis of HEV; however, rapid bedside diagnostics are available and could offer a practical alternative, especially in low-income countries. One vaccine (HEV 239) is only available in China and Pakistan, as efficacy against the other genotypes remains uncertain. The effectiveness trial conducted in Bangladesh might lead the way in gathering more efficacy data and could, together with improved surveillance and raised awareness, dramatically reduce the global burden of HEV.

Epidemiological Profile of a Human Hepatitis E Virus Outbreak in 2018, Chattogram, Bangladesh

Hepatitis E virus (HEV) is a waterborne zoonotic disease that can result in a high fatality rate in pregnant women and infants. In 2018, a large HEV outbreak emerged in Chattogram, Bangladesh, resulting in 2800 cases and a significant public health response to mitigate the transmission. While the source of the outbreak remained poorly understood, authorities suggested that possible risk factors for HEV infection included contamination of water supply, exacerbated by concurrent severe flooding events in the community. A cross-sectional study was conducted to investigate the distribution and risk factors for HEV seroprevalence between January and December 2018 in the Chattogram city area. A total of 505 blood samples were collected from symptomatic patients of 10 hospitals who met the case definition for an HEV infection. Standard ELISA tests were performed in all patients to identify anti-HEV antibodies. The size and location of HEV seroprevalence clusters within Chattogram were investigated using SaTScan. We investigated the association between risk of HEV infection and individual and environmentally lagged risk factors using Bernoulli generalised linear regression models. Our results indicate an overall HEV seroprevalence of 35% with significant variation according to sex, source of drinking water, and boiling of drinking water. A positive cross-correlation was found between HEV exposure and precipitation, modified normalised difference water index (MNDWI), and normalised difference vegetation index (NDVI). Our model indicated that risk of infection was associated with sex, age, source of drinking water, boiling of water, increased precipitation, and increased MNDWI. The results from this study indicate that source and boiling of drinking water and increased precipitation were critical drivers of the 2018 HEV outbreak. The communities at highest risk identified in our analyses should be targeted for investments in safe water infrastructure to reduce the likelihood of future HEV outbreaks in Chattogram.

Drivers of zoonotic disease risk in the Indian subcontinent: A scoping review

Literature on potential anthropogenic drivers of zoonotic disease risk in the Indian subcontinent is sparse. We conducted a scoping review to identify primary sources, published 2000-2020, to clarify what research exists and on which areas future research should focus. We summarised findings thematically by disease. Of 80 sources included, 78 (98%) were original research articles and two were conference abstracts. Study designs and methods were not always clearly described, but 74 (93%) were quantitative (including one randomised trial), five (6%) were mixed-methods, and one was qualitative. Most sources reported research from India (39%) or Bangladesh (31%), followed by Pakistan (9%), Nepal (9%), Bhutan and Sri Lanka (6% each). Topically, most focused on rabies (18; 23%), Nipah virus (16; 20%) or leptospirosis (11; 14%), while 12 (15%) did not focus on a disease but instead on knowledge in communities. People generally did not seek post-exposure prophylaxis for rabies even when vaccination programmes were available and they understood that rabies was fatal, instead often relying on traditional medicines. Similarly, people did not take precautions to protect themselves from leptospirosis infection, even when they were aware of the link with rice cultivation. Nipah was correlated with presence of bats near human habitation. Official information on diseases, modes of transmission and prevention was lacking, or shared informally between friends, relatives, and neighbours. Behaviour did not correspond to disease knowledge. This review identifies various human behaviours which may drive zoonotic disease risk in the Indian subcontinent. Increasing community knowledge and awareness alone is unlikely to be sufficient to successfully change these behaviours. Further research, using interdisciplinary and participatory methods, would improve understanding of risks and risk perceptions and thus help in co-designing context-specific, relevant interventions.

Swine hepatitis E virus: Cross-species infection, pork safety and chronic infection

Swine hepatitis E virus (swine HEV) belongs to the species Orthohepevirus A within the genus Orthohepevirus in the family Hepeviridae. Four different genotypes of swine HEV within the species Orthohepevirus A have been identified so far from domesticated and wild swine population: genotypes 3 (HEV-3) and 4 (HEV-4) swine HEVs are zoonotic and infect humans, whereas HEV-5 and HEV-6 are only identified from swine. As a zoonotic agent, swine HEV is an emerging public health concern in many industrialized countries. Pigs are natural reservoir for HEV, consumption of raw or undercooked pork is an important route of foodborne HEV transmission. Occupational risks such as direct contact with infected pigs also increase the risk of HEV transmission in humans. Cross-species infection of HEV-3 and HEV-4 have been documented under experimental and natural conditions. Both swine HEV-3 and swine HEV-4 infect non-human primates, the surrogates of man. Swine HEV, predominantly HEV-3, can establish chronic infection in immunocompromised patients especially in solid organ transplant recipients. The zoonotic HEV-3, and to lesser extent HEV-4, have also been shown to cause neurological diseases and kidney injury. In this review, we focus on the epidemiology of swine HEV, host and viral determinants influencing cross-species HEV infection, zoonotic infection and its associated pork safety concern, as well as swine HEV-associated chronic infection and neurological diseases.

High prevalence of hepatitis E virus infection among domestic pigs in Ibaraki Prefecture, Japan

BACKGROUND

Hepatitis E virus (HEV) is prevalent in pigs and may serve as a reservoir for human infection. However, data on HEV infections in pigs in Ibaraki Prefecture, Japan, are limited. Here, we clarified the process and course of HEV in naturally infected pigs. Serum (n = 160) and liver (n = 110) samples were collected from pigs at the slaughterhouse. Furthermore, serum samples were collected from 45 breeding sows and serum and feces samples were collected from 7 piglets once a week (raised until 166 days of age). HEV antigen and antibodies were evaluated, and the genotype was identified based on molecular phylogenetic tree analysis.

RESULTS

The samples collected from the slaughterhouse revealed that few pigs were HEV carriers but most possessed anti-HEV antibodies. Most breeding sows possessed antibodies, and the piglets excreted HEV on the farm at approximately 10 weeks of age. One pig was initially infected, and in a few weeks, the other pigs living in the same sty became infected.

CONCLUSIONS

Most pigs in Ibaraki Prefecture were with HEV. On the farm, most piglets were infected with HEV by the time they reached slaughter age. We confirmed that HEV infection is successively transmitted among piglets living in the same sty.

Short communication: detection and molecular characterization of hepatitis E virus in domestic animals of São Tomé and Príncipe

As in most of the African continent, the status of hepatitis E virus (HEV) infection in domestic animals in São Tomé and Príncipe, an archipelago off the western equatorial coast of Central Africa, is also completely unknown. In the present study, we investigated the presence of HEV among domestic animals in São Tomé and Príncipe. A total of 93 stool samples from different animal species (goat, cow, pig, chicken, duck, and monkey) were tested for HEV RNA using two real-time RT-PCR assays, followed by a nested RT-PCR assay for sequencing and phylogenetic analysis. A total of six samples (1 cow stool and 5 pig stools) were found to be positive for HEV RNA of which one pig stool was positive by broad spectrum nested RT-PCR. Phylogenetic analysis showed that the retrieved sequence clustered within HEV subgenotype 3f, similar to zoonotic strains of European countries and posing interesting questions on past introduction of European HEV into São Tomé and Príncipe archipelago. This is the first report describing the presence and molecular characterization of HEV in São Tomé and Príncipe.

Phylogenetic Analysis and Characterization of the Complete Hepatitis E Virus Genome (Zoonotic Genotype 3) in Swine Samples from Mexico

Hepatitis E virus (HEV) is an emerging public health problem with an estimated 20 million infections each year. In Mexico, Orthohepevirus A, genotype 2, has been reported in humans, but genotype 3 has only been reported in swine (zoonotic). No diagnostic tests are publicly available in Mexico, and only partial sequences have been reported from swine samples. Hence, research is necessary to determine circulating strains, understand the features and dynamics of infection on pig farms, determine how to implement surveillance programs, and to assess public health risks. In this study, a next-generation sequencing (NGS) approach was applied to obtain a complete genome of swine HEV. Liver, feces, and bile samples were taken at slaughterhouses and a farm in Mexico. RT-PCR was used to determine positive samples and confirmed by Sanger sequencing. Of the 64 slaughterhouse samples, one bile sample was positive (B1r) (1.56%). Of 21 sample pools from farm animals, 14 were positive (66.66%), representing all stages of production. A complete sequence strain MXCDg3_B1c|_2016 was obtained from the bile of a domestic swine in the fattening stage. In addition, two partial sequences—MXCDg3_H2cons|_2016 (1473 nt) and MXCDg3_C3Acons|_2016 (4777 nt)—were obtained from sampled farm animals. Comparison with all reported genome HEV sequences showed similarity to genotype 3 subgenotype a (G3a), which has been previously reported in acute cases of human hepatitis in the US, Colombia, China, and Japan.

Establishment of a Competitive Binding Assay Identifying the Different Characteristics of Neutralizing Epitopes of Hepatitis E Virus

AIMS

To confirm the different characteristics of genotype-specific and common neutralizing epitopes of hepatitis E virus (HEV).

METHODS

A competitive binding assay was established with known genotype-common neutralizing monoclonal antibodies (mAbs) 3G1 and 5G5 as well as genotype-specific neutralizing mAbs 2B1 and 4C5. HEV ORF2 recombinant p166W01 derived from genotype 1 and p166Chn derived from genotype 4 were used as coated antigens, to determine whether the mAbs recognize independent, similar, or overlapping epitopes. mAbs were produced, purified, and conjugated with horseradish peroxidase (HRP). HRP-conjugated 2B1 could react only with p166W01 but not p166Chn, HRP-conjugated 4C5 could react only with p166Chn but not p166W01, while HRP-conjugated 3G1 and 5G5 could react both with p166W01 and p166Chn. Thus, competitive binding assays were performed successively using p166W01 and p166Chn antigen.

RESULTS AND CONCLUSION

The results of competitive binding assays revealed that the binding of HRP-conjugated 2B1 to p166W01 could not be inhibited by 5G5 or 3G1. Similarly, the binding of HRP-conjugated 4C5 to p166Chn could not be inhibited by 5G5 or 3G1. However, the mAbs 5G5 and 3G1 blocked each other's binding to p166W01 and p166Chn, suggesting that common and genotype-specific neutralizing mAbs recognize independent epitopes.