A cross-sectional study of hepatitis E virus infection in pigs in different-sized farms in northern Thailand

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.

Seroepidemiological Survey of Hepatitis E Virus in Intensive Pig Farming in Vojvodina Province, Serbia

Hepatitis E virus (HEV) is the causative agent of acute hepatitis E infection in humans. Two epidemiological patterns of the disease exist-endemic and sporadic. Genotypes 1 (HEV-1) and 2 (HEV-2) are transmitted through contaminated water and are responsible for the outbreaks of many large-scale epidemics in developing countries of Asia and Africa. Genotypes 3 (HEV-3) and 4 (HEV-4) have zoonotic potential and cause sporadic cases and small outbreaks in high-income countries. The first case of HEV infection in swine was confirmed in 1997 and later detected in other animal species. The aim of this study was to investigate the seroprevalence of HEV infection in pig farms in Vojvodina province, Serbia. Three hundred blood samples were collected from five different categories of pigs from 3 different farms on the territory of the South Bačka district in Vojvodina (Serbia). The analyses were conducted by in-house ELISA, while the western blot method was used as a confirmatory test for doubtful results. The presence of HEV IgG was detected on all three examined farms. The established seroprevalence in Farm A was 37%, 31% in Farm B, and 54% in Farm C. The mean seroprevalence for all farms was 40.66%. A higher seroprevalence was found in fatteners compared to younger categories of pigs. We concluded that HEV is widespread on pig farms with intensive management. Further analyses should be conducted with the aim of implementing a surveillance program to prevent possible human infection.

Characterization of zoonotic hepatitis E virus in domestic pigs and wild boar in Vietnam: Implications for public health

Vietnam's unprecedented demand for meat from livestock, including pigs and farmed wildlife, underscores the importance of understanding zoonotic reservoirs for hepatitis E virus (HEV). This study aimed to identify and characterize circulating zoonotic HEV in domestic pigs and wild boar to understand genotype frequencies, transmission dynamics, and associated human health burdens. Rectal swabs, feces, and liver samples from 415 pigs and 102 wild boars were collected across various farms and slaughterhouses in central and southern Vietnam and screened for HEV RNA using nested PCR. HEV RNA-positive samples underwent sanger sequencing and genotyping. Overall, 10% (n = 54/517) of samples were HEV RNA-positive, with wild boars exhibiting the highest HEV positivity rate at 25%, followed by domestic pigs at 7%. Southern Vietnam showed a higher HEV RNA positivity rate (20%) compared to central Vietnam (7%). Notably, rectal swabs demonstrated the highest positivity rate (15%), followed by feces (8%) and liver (4%). HEV-3a was the predominant genotype at 85%, followed by HEV-4b at 9% and HEV-3f at 6%. While HEV-3a was distributed across both central and southern Vietnam, HEV-3f was exclusively detected in central Vietnam, and HEV-4b was identified in wild boar in southern Vietnam. These findings underscore the substantial prevalence of HEV in wild boars, emphasizing their potential as crucial zoonotic reservoirs alongside domestic pigs. Further investigations involving occupationally exposed individuals in high-prevalence areas are warranted to evaluate the human health impact of zoonotic hepatitis E and inform preventive measures. Regular epidemiological studies are imperative for assessing the prevalence and transmission of zoonotic HEV infections among common reservoirs, thereby aiding in the prevention of spillover events within the community.

Unraveling swine hepatitis E in the central region of Argentina through ELISA development and epidemiological insights

Hepatitis E virus (HEV) is a public health concern globally, causing acute viral hepatitis in humans. Genotype-3 HEV (HEV-3), the most frequently genotype detected in South America, is zoonotic and the main reservoirs are the domestic pig and wild boar. Circulation of HEV-3 in Argentina has been confirmed in humans as well as in pig herds, wild boar and environmental waters. However, data are scarce mainly due to the inaccessibility of serological assays in this country. In order to provide insights in the epidemiology of HEV in swine in Argentina, we developed an indirect ELISA based on the native recombinant protein ORF2 and conducted a serological survey to determine the prevalence of seropositive swine in small-scale pig farms in the central region of Argentina. The method was evaluated in a panel of 157 serum samples, resulting in relative sensitivity of 98.6 % (95 % CI 95 %-100 %) and relative specificity of 97.7 % (95 % CI 94 %-100 %) compared to a commercial test. An almost perfect agreement was obtained between the two tests (Kappa index of 0.961). A survey on 294 samples from 49 small-scale farms resulted in a seropositivity rate of 54 %. Seropositive animals were found in 34 out of 49 (69.4 %) farms. Most of the farms (70.6 %) had over 50 % of seropositive animals. The wide spreading of HEV in the swine population of Tandil, Argentina, underscore the need to better understand the epidemiology of HEV in the region, enabling the implementation of targeted interventions to mitigate the impact of this virus on public health.

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) in Heavy Pigs in Slaughterhouses of Northern Italy: Investigation of Seroprevalence, Viraemia, and Faecal Shedding

Hepatitis E virus (HEV) is considered an emerging threat in Europe, owing to the increased number of human cases and the widespread presence of the virus in pigs at farms. Most cases in industrialized countries are caused by the zoonotic HEV-3 genotype. The main transmission route of HEV-3 in Europe is foodborne, through consumption of raw or undercooked liver pork and wild boar meat. Pigs become susceptible to HEV infection after the loss of maternal immunity, and the majority of adult pigs test positive for IgG anti-HEV antibodies. Nonetheless, HEV-infected pigs in terms of liver, faeces, and rarely blood are identified at slaughterhouses. The present study aimed to investigate the prevalence of HEV-positive batches of Italian heavy pigs at slaughterhouses, assessing the presence of animals still shedding HEV upon their arrival at the slaughterhouse by sampling faeces collected from the floor of the trucks used for their transport. The occurrence of viraemic animals and the seroprevalence of anti-HEV antibodies were also assessed. The results obtained indicated the presence of anti-HEV IgM (1.9%), and a high seroprevalence of anti-HEV total antibodies (IgG, IgM, IgA; 89.2%, n = 260). HEV RNA was not detected in either plasma or faecal samples. Nevertheless, seropositive animals were identified in all eight batches investigated, confirming the widespread exposure of pigs to HEV at both individual and farm levels. Future studies are needed to assess the factors associated with the risk of HEV presence on farms, with the aim to prevent virus introduction and spread within farms, thereby eliminating the risk at slaughterhouse.

A Randomized Large-Scale Cross-Sectional Serological Survey of Hepatitis E Virus Infection in Belgian Pig Farms

Hepatitis E virus (HEV) is the causative agent of hepatitis E disease in humans. While sporadic HEV infections, which occur in industrialised countries and are typically due to HEV genotypes 3 or 4, are asymptomatic and self-limiting, a chronic form of the disease can lead to liver cirrhosis in immunocompromised individuals. Pigs share HEV 3 and 4 genotypes and are thus considered a major animal reservoir for human infection. A subset of animals has been shown to carry HEV particles at the age of slaughter, rendering raw or undercooked pig products potential vectors for human infection. To provide an overview of the current dissemination of HEV in Belgian pig herds, this study was designed as a randomized, robust, large-scale, cross-sectional, serological survey. HEV genotypes and subtypes recently circulating in Belgium (2020-2021) were investigated. Sample stratification as well as epidemiological investigation through the available demographic data of the sampled herds showed that HEV widely circulated in the Belgian pig population during this time and that a change in the circulating HEV strains may have occurred in the last decade. Herd size and type were identified as risk factors for HEV herd-seropositivity. Identifying farms at risk of being HEV-positive is an important step in controlling HEV spread and human infection.

Epidemiological survey and risk factors associated with hepatitis E virus in small ruminants in southern Spain

Autochthonous cases of hepatitis E (HE) associated with zoonotic genotypes HEV-3 and HEV-4 have significantly increased in industrialized countries over the last decade. Suidae are generally recognized as the main reservoirs of these genotypes. Susceptibility to HE virus (HEV) infection and zoonotic potential have also been confirmed in other species, including sheep and goat. However, the information about their role in the epidemiology of HEV remains very scarce. The objective of this study was to assess the prevalence, spatial distribution and risk factors associated with HEV exposure in sheep and goats in southern Spain, the country with the highest census of small domestic ruminants in the European Union. Blood samples from 240 sheep and 240 goats were collected between 2015 and 2017. Sera were analysed in parallel using a commercial double-antigen ELISA and real-time PCR. A total of 38 (7.9%; 95%CI: 5.5-10.3) out of 480 sampled animals showed anti-HEV antibodies. By species, the seroprevalences found in sheep and goats were 2.1% (5/240; 95%CI: 0.3-3.9) and 13.8% (33/240; 95%CI: 9.4-18.1) respectively. Anti-HEV antibodies were found on 19 (59.4%; 95%CI: 42.4-76.4) of the 32 sampled farms. The GEE model showed that species (goat) and number of small ruminants in the farm (≤348 animals and ≥538 animals) were risk factors potentially associated with HEV exposure in small ruminants in the study area. HEV RNA was not detected in any of the 480 (0.0%; 95%CI: 0.0-0.8) tested animals. Our results confirm that sheep and goats are naturally, but not equally exposed to HEV and indicate the widespread spatial distribution of HEV among small ruminant populations in southern Spain. Further studies are required to elucidate the role of sheep and goat in the epidemiology of HEV and their potential implications for public health.

Porcine Blood and Liver as Sporadic Sources of Hepatitis E Virus (HEV) in the Production Chain of Offal-Derived Foodstuffs in Poland

Pig's blood and liver are valuable edible slaughter by-products which are also the major ingredients of offal-derived foodstuffs. The aim of the study was an evaluation of the occurrence of hepatitis E virus (HEV) and porcine adenovirus (pAdV) as an index virus of faecal contamination in pig's blood and liver for human consumption. In total, 246 samples of retail liver (n = 100) and pooled pig's blood (n = 146) were analysed for the presence of HEV and pAdV. Blood samples were individually collected from 1432 pigs at slaughter age. Viral genomic material, including RNA of a sample process control virus was isolated from food samples using a QIAamp® Viral RNA Mini Kit. Virus-specific IAC-controlled real-time PCR methods were used for detection of target viruses. HEV RNA was found in 6 (2.4%; 95% CI: 0.9-5.2) out of 246 samples of tested foodstuffs. The virus was detected in pig's blood (3.4%; 95% CI: 1.1-7.8) and liver (1.0%; 95% CI: 0.0-5.0) with no significant differences observed in the frequency of its occurrence between the two by-products (t = 1.33; p = 0.182 > 0.05); however PAdV was detected more frequently in pig's blood than in liver (t = 4.65; p = 0.000 < 0.05). The HEV strains belonged to the 3f and 3e subtype groups and the pAdV strains were assigned to serotype 5. PAdV was detected in pigs regardless of the farm size from which they originated. The number of animals raised on the farm (the farm size) had no influence on the occurrence of HEV or pAdV infections in pigs (F = 0.81, p = 0.447 > 0.05 for HEV; F = 0.42, p = 0.655 > 0.05 for pAdV). Although HEV was detected in pig's offal only sporadically, consumers cannot treat its occurrence with disregard as it demonstrates that HEV-contaminated pig tissues can enter the food chain.

Seroprevalence and phylogenetic characterization of hepatitis E virus in pig farms in Southern Italy

Hepatitis E virus (HEV) infection is an emerging public health problem in industrialized countries. The infection is associated with waterborne epidemics and transmitted via faecal-oral route. Zoonotic cases of HEV in humans have increased in Europe, and HEV genotype 3 (HEV-3) is the most frequent among humans and animals. Nevertheless, HEV surveillance in the Italian pig farming industry is patchy. Here, HEV prevalence in pig farms located in the Calabria region in Southern Italy was investigated. A total of 692 serum samples were collected from 26 farms and tested for anti-HEV IgG antibody detection. The percentage of HEV-seropositive pigs was 56.8 %. Small farm size, farrow-to-finishing production, and infrequent cleaning procedures were associated with higher HEV seroprevalence. In 12 of the HEV-seropositive farms, 67 faecal samples were collected and 10 of these (10.6 %) tested positive for HEV RNA. Seven of 10 viral RNA sequences were genotyped for phylogenetic analysis, five of which belonged to subtype HEV-3f and two to subtype HEV-3e. The high HEV seroprevalence and the circulation of HEV-3 strains among domestic pigs in the Calabria region pose a risk for the zoonotic transmission of HEV from pigs to occupational exposed workers.

Prevalence and phylogenetic analysis of hepatitis E virus in pigs in Vietnam

Background

Hepatitis E virus (HEV) is a zoonotic disease and has been reported around the world. The main objective of this study was to evaluate the sero-prevalence and phylogenetic analysis of HEV in Vietnam. Pig blood and fecal pooled samples were collected to assess the prevalence of HEV. We assessed the true prevalence (TP) of HEV from apparent prevalence (AP) by taking into account the sensitivity and specificity of diagnostic tests using a Bayesian approach. For phylogenetic analysis, the data compared with worldwide HEV reference strains including all eight genotypes (G1-G8) which were identified in previous study.

Results

A total of 475 sera and 250 fecal pooled samples were collected at slaughterhouses and pig farms from five provinces, in Viet Nam. Overall, the sero-AP of HEV was 58.53% (95% confidence interval: 53.95–62.70) while the sero-TP was slightly higher (65.43, 95% credible interval: 47.19–84.70). In terms of pooled samples, overall, the RNA-AP was 6.80% (95% confidence interval: 4.01–10.66). One strain in Hanoi, two strains in Dak Lak, seven strains in An Giang, four strains in Son La and two strains in Nghe An were isolated. The phylogenetic tree demonstrated that 19 Vietnamese strains were clustered into HEV 3 and 4.

Conclusions

This study provided evidence that HEV is circulating in domestic pigs in Vietnam. From a public health perspective, it is very important to raise public awareness for high-risk groups (e.g. slaughterhouse workers, pig traders, farmers and market sellers) who have more opportunities to come in contact with pig and contaminated meats.

A between-herd data-driven stochastic model to explore the spatio-temporal spread of hepatitis E virus in the French pig production network

Hepatitis E virus is a zoonotic pathogen for which pigs are recognized as the major reservoir in industrialised countries. A multiscale model was developed to assess the HEV transmission and persistence pattern in the pig production sector through an integrative approach taking into account within-farm dynamics and animal movements based on actual data. Within-farm dynamics included both demographic and epidemiological processes. Direct contact and environmental transmission routes were considered along with the possible co-infection with immunomodulating viruses (IMVs) known to modify HEV infection dynamics. Movements were limited to 3,017 herds forming the largest community on the swine commercial network in France and data from the national pig movement database were used to build the contact matrix. Between-herd transmission was modelled by coupling within-herd and network dynamics using the SimInf package. Different introduction scenarios were tested as well as a decrease in the prevalence of IMV-infected farms. After introduction of a single infected gilt, the model showed that the transmission pathway as well as the prevalence of HEV-infected pigs at slaughter age were affected by the type of the index farm, the health status of the population and the type of the infected farms. These outcomes could help design HEV control strategies at a territorial scale based on the assessment of the farms' and network's risk.

Controlling hepatitis E virus in the pig production sector: Assessment of the technical and behavioural feasibility of on-farm risk mitigation strategies

Hepatitis E virus (HEV) is a zoonotic agent with pigs as the main reservoir in industrialised countries. Recent studies conducted on pig farms, in experimental conditions or through modelling approaches, have led to a better understanding of the spread of HEV on pig farms. The findings have also made it possible to define a set of measures to reduce HEV prevalence and the risk of marketing contaminated products. The objective of this study was to assess the feasibility of a set of HEV control strategies on pig farms. Individual semi-structured interviews were conducted with farmers, veterinarians and farming advisors to collect general data, their level of knowledge of HEV, their opinion on the technical feasibility of certain changes in practices, their perception of the respective responsibilities of the different stakeholders, and their feelings about the importance of the issue, following the framework of the Theory of Planned Behaviour. The interviews made it possible to highlight potential barriers and preferred motivators for the implementation of on-farm risk mitigation strategies. Barriers included lack of knowledge, scientific gaps, perceived inability to control HEV, and low perception of the importance of the issue. Motivators included professional satisfaction, family recognition, and the opportunity to achieve higher quality standards. Three clusters of stakeholders were also identified, with a group of leaders who could help unlock reluctance and disseminate innovations. This type of behavioural approach appeared useful to help risk managers facilitate zoonotic control on pig farms.

Natural viral co-infections in pig herds affect hepatitis E virus (HEV) infection dynamics and increase the risk of contaminated livers at slaughter

Hepatitis E virus (HEV) is a zoonotic pathogen, in particular genotype 3 HEV is mainly transmitted to humans through the consumption of contaminated pork products. This study aimed at describing HEV infection patterns in pig farms and at assessing the impact of immunomodulating co-infections namely Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Porcine Circovirus Type 2 (PCV2), as well as other individual factors such as piglets' immunity and litters' characteristics on HEV dynamics. A longitudinal follow-up was conducted in three farrow-to-finish farms known to be HEV infected. Overall, 360 piglets were individually monitored from birth to slaughter with regular blood and faecal sampling as well as blood and liver samples collected at slaughterhouse. Virological and serological analyses were performed to detect HEV, PCV2 and PRRSV genome and antibodies. The links between 12 explanatory variables and four outcomes describing HEV dynamics were assessed using cox-proportional hazard models and logistic regression. HEV infection dynamics was found highly variable between farms and in a lower magnitude between batches. HEV positive livers were more likely related to short time-intervals between HEV infection and slaughter time (<40 days, OR = 4.1 [3.7-4.5]). In addition to an influence of piglets' sex and sows' parity, the sequence of co-infections was strongly associated with different HEV dynamics: a PRRSV or PCV2/PRRSV pre- or co-infection was associated with a higher age at HEV shedding (Hazard Ratio = 0.3 [0.2-0.5]), as well as a higher age at HEV seroconversion (HR = 0.5 [0.3-0.9] and HR = 0.4 [0.2-0.7] respectively). A PCV2/PRRSV pre- or co-infection was associated with a longer duration of shedding (HR = 0.5 [0.3-0.8]). Consequently, a PRRSV or PCV2/PRRSV pre- or co-infection was strongly associated with a higher risk of having positive livers at slaughter (OR = 4.1 [1.9-8.9] and OR = 6.5 [3.2-13.2] respectively). In conclusion, co-infections with immunomodulating viruses were found to affect HEV dynamics in the farrow-to-finish pig farms that were followed in this study.

Seroepidemiology of hepatitis E virus infection in pigs in Durango State, Mexico

No information about hepatitis E virus (HEV) infection in pigs in the northern Mexican state of Durango exists. We determined the seroprevalence and correlates of anti-HEV IgG antibodies in pigs in Durango, Mexico. Through a cross-sectional study, we studied 427 pigs raised in backyards (n = 328), or slaughtered (n = 99) in Durango. Sera of pigs were analyzed for anti-HEV IgG antibodies using a commercially available enzyme-linked immunoassay. Antibodies to HEV were found in 193 (45.2%) of the 427 pigs studied. A significantly higher seroprevalence was observed in slaughtered pigs (79.8%) than in backyard pigs (34.8%). Bivariate analysis showed that HEV seropositivity was associated with age, sex, breed, climate, altitude, mean annual temperature, mean annual rainfall, and farm raising. Logistic regression analysis showed that HEV seropositivity was associated with the origin (Sonora State) of pigs (OR=6.51; 95%CI: 3.74-11.32; P < 0.001), and mean annual rainfall (≤600 mm) (OR=1.78; 95%CI: 1.01-3.15; P = 0.04). A high seroprevalence of HEV infection in pigs slaughtered for human consumption in Durango City was found. This is the first report of an association between HEV seropositivity in pigs and climatic factors. Infection factors found may help for the optimal planning of preventive measures against HEV infection.

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.

Seroepidemiology and molecular characterization of hepatitis E virus infection in swine and occupationally exposed workers in Punjab, India

Hepatitis E virus (HEV) has two discrete epidemiological patterns: waterborne epidemics in developing countries only, caused by HEV genotype I, and sporadic zoonotic outbreaks in developing and developed countries caused by genotypes III and IV. This study was designed to investigate seroprevalence, molecular detection and the characterization of HEV by nested RT-PCR in swine as well as the occupational risk to exposed human population in Punjab state of north-western India. The occupational risk-exposed group comprised of swine farmers (organized - mixed feed feeders and unorganized - swill feeders), slaughterhouse workers, sewage workers and veterinary internes. During the study period, blood and faecal samples were collected from 320 swine and 360 humans with both high and low occupational exposure risks. The overall seroprevalence of swine HEV was 65.00%, with a significantly higher seropositivity in growing pigs (2-8 months of age). The prevalence of HEV RNA in swine faecal samples by nRT-PCR was 8.75% with a significantly higher detection in swill-fed pigs. With humans in the high occupational exposure risk population, significantly higher anti-HEV IgG seropositivity was observed (60.48%) as compared to control population (10.71%). Strong evidence of association between human anti-HEV IgG seropositivity and certain occupational exposure risk groups was observed (p < 0.05). This indicates that unorganized swine farmers, slaughterhouse workers and sewage workers have higher odds of HEV infection in this study region. Percentage of nucleotide similarity between swine and human HEV isolates was less than that found in countries with zoonotic HEV outbreaks. Molecular characterization revealed the circulation of G IV and G I genotypes among swine and human population in Punjab state, respectively.

Hepatitis E Virus in Pork and Variety Meats Sold in Fresh Markets

Swine is an economically important livestock, yet pork consumption and close contact with pigs are associated with the risk of hepatitis E virus (HEV) infection. Limited data on the prevalence of HEV in Southeast Asia have mainly examined farm animals. To investigate the potential zoonotic transmission of HEV from dietary consumption of pork and variety meats (i.e., offal or organ meats), we obtained 1090 liver, 559 pork meat, and 556 intestine samples from fresh markets in the Bangkok metropolitan area between November 2014 and February 2015. The presence of HEV was assessed using reverse-transcription polymerase chain reaction. Concurrently, 720 bile and 553 fecal samples from a slaughterhouse were also examined. Overall, HEV RNA was found in 0.23 % of the market samples and 3.93 % of the slaughterhouse samples. Fecal and bile samples were more likely to test positive compared to liver, pork, and intestine samples (p < 0.001). Phylogenetic analysis showed that all HEV sequences obtained in this study formed a cluster closely related to genotype 3f. Pork and variety meats derived from pigs are commonly sold in fresh markets throughout Southeast Asia. Here, a relatively low HEV prevalence from pork and variety meats sold in Bangkok was found. Additional studies will be required to further assess potential dietary transmission of HEV elsewhere in the region.

Hepatitis E in Singapore: A Case-Series and Viral Phylodynamics Study

AbstractThe incidence of hepatitis E in Singapore appears to be increasing. A retrospective case-series study of patients diagnosed with hepatitis E in a tertiary hospital from 2009 to 2013 was conducted. Of 16 cases, eight (50%) were solid-organ transplant recipients (SOTRs), and 14 (88%) were found infected by genotype 3 hepatitis E virus (HEV-3). Bayesian inferences based on HEV subgenomic sequences from seven cases suggest that HEV-3 strains were introduced to Singapore as two principal lineages. Within limitations of the study, it can be inferred that one lineage, in the 3efg clade, emerged about 83 years ago, probably originating from Japan, whereas the other, in the 3abchij clade, emerged about 40 years ago, from the United States. Establishment and subsequent transmissions of strains from these two lineages likely contribute to the current endemicity of hepatitis E in Singapore.

Pork consumption and seroprevalence of hepatitis E virus,Thailand, 2007-2008

The nationwide seroprevalence of hepatitis E IgG was determined among young men in Thailand. Overall seroprevalence was 14% (95% CI 13%–15%); range by province was 3%–26%. Seroprevalence was lowest in the south, an area predominantly occupied by persons of the Islam religion, whose dietary laws proscribe pork.

Swine is a possible source of hepatitis E virus infection by comparative study of hepatitis A and E seroprevalence in Thailand

Hepatitis A virus (HAV) and hepatitis E virus (HEV) infection in developing countries are associated with contaminated food or water. Although Thailand is non-endemic for HEV, sporadic infections may occur from zoonotic transmission. Individuals between 7 months to 69 years (mean age = 32.8) from predominantly Islamic Narathiwat (n = 305) and swine farm-dense Lop Buri (n = 416) provinces were screened for anti-HEV and anti-HAV antibodies by commercial enzyme-linked immunosorbent assay and automated chemiluminescent microparticle immunoassay, respectively. Seroprevalence and relative antibody titers were analyzed according to age groups. HAV IgG antibody positive rates in Lop Buri and Narathiwat residents were 39.9% and 58%, respectively (p < 0.001). Greater than 90% of individuals >50 years old in both provinces possessed anti-HAV IgG. In contrast, seroprevalence for anti-HEV IgG was much higher in Lop Buri (37.3%) than in Narathiwat (8.9%) (p < 0.001). Highest anti-HEV IgG prevalence was found among 21-30 year-olds (50%) in Lop Buri and 41-50 year-olds (14.1%) in Narathiwat. In summary, fewer individuals possessed anti-HEV IgG in Narathiwat where most residents abstained from pork and fewer swine farms are present. Therefore, an increased anti-HEV IgG seroprevalence was associated with the density of swine farm and possibly pork consumption. Adults were more likely than children to have antibodies to both HEV and HAV.

Seroprevalence and molecular characteristics of hepatitis E virus in household-raised pig population in the Philippines

Background

Hepatitis E virus (HEV) infection is a significant public health concern in Asia, and swine is an important source of sporadic HEV infection in human. However, no epidemiological data are available regarding HEV infection among the swine or human population in the Philippines. To assess the HEV infection status among pigs in rural areas, we investigated the molecular characteristics and seroprevalence of HEV among household-raised pigs in San Jose, Tarlac Province, the Philippines.

Result

Serum and rectal swab samples were collected from 299 pigs aged 2–24 months from 155 households in four barangays (villages) between July 2010 and June 2011. Enzyme-linked immunosorbent assay (ELISA) revealed that 50.3% [95% confidence interval (CI) 44.5–56.2%] and 22.9% (95% CI 18.2–28.1%) of pigs tested positive for anti-HEV IgG and IgM, respectively. HEV RNA was detected in the feces of 22 pigs (7.4%, 95% CI 4.7–10.9%). A total of 103 households (66.5%, 95% CI 58.4–73.8%) had at least one pig that tested positive for anti-HEV IgG or IgM or HEV RNA. The prevalence of anti-HEV IgG and IgM in breeding pig (8–24 months) were higher than that in growing pigs (2–4 months) (p < 0.0001 and p = 0.008, respectively). HEV RNA was more frequently detected in 2–4-month-old pigs (9.2%, 95% CI 5.4–14.6%) than in ≥5-month-old pigs (4.8%, 95% CI 1.1–8.5%) without statistical significance (p = 0.142). HEV RNA showed 0–27.6% nucleotide difference at the partial ORF2 gene among the detected viruses, and a majority of them belonged to subtype 3a (20/22, 90.9%).

Conclusion

We found a high prevalence of HEV antibodies in the household-raised pig population in rural areas of the Philippines, which indicates the potential risk of HEV infection among local residents. Only genotype 3 of HEV was observed, and genetically diverse strains of HEV were found to be circulating in pigs in this study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0322-z) contains supplementary material, which is available to authorized users.