Infection dynamics of hepatitis E virus in naturally infected pigs in a Chinese farrow-to-finish farm

Detection of antibodies to the hepatitis E virus in domestic reindeer (Rangifer tarandus) in the Republic of Sakha (Yakutia)

INTRODUCTION

Although domestic pigs and wild boars are the main reservoir of zoonotic hepatitis E virus (HEV) genotypes in temperate countries, the presence of antibodies to HEV (anti-HEV) in the indigenous population of circumpolar territories, i.e. outside the habitat of wild and domestic pigs, indicates the presence of an alternative reservoir of the virus. Reindeer (Rangifer tarandus) may be a potential reservoir for HEV in the polar regions. The purpose of the study was to determine the prevalence of anti-HEV among domestic reindeer in the Republic of Sakha (Yakutia).

MATERIALS AND METHODS

Sera from 497 domestic reindeer from the Oymyakon (n = 425) and Ust-Yansky districts (n = 72) of the Republic of Sakha (Yakutia) were tested for anti-HEV. A commercial ELISA kit DS-ELISA-ANTI-HEV-G (Diagnostic Systems-Stolitsa LLC, Russia) was used for detection of anti-HEV IgG, but a rabbit polyclonal antibody against deer IgG labeled with horseradish peroxidase (KPL, USA) at a dilution of 1 : 100 in phosphate-buffered saline were used instead of the human specific conjugate from the kit.

RESULTS

The average detection rate of anti-HEV in reindeer sera was 15.5% (95% CI: 12.6-19.0%). The detection rate of anti-HEV significantly increased with age, from 3.5% (95% CI: 1.1-9.0%) in calves aged 3-6 months to 25.0% (95% CI: 1.6 -36.5%) in deer aged 2-4 years (p < 0.0001). From this age group, anti-HEV detection rates reached a plateau, not differing significantly between older age groups (p > 0.05). The average anti-HEV detection rate among reindeer 2 years of age and older was 19.0% (95% CI: 15.3-23.4%). There were no statistically significant differences in the frequency of anti-HEV detection between female and male reindeer, both among adult animals and among calves.

CONCLUSION

The observed anti-HEV detection rates among domestic reindeer in the Republic of Sakha (Yakutia) indicate that infection caused by HEV or an antigenically similar virus is common in these animals. The dynamics of antibody accumulation in the reindeer population indicates that infection apparently occurs during the first two years of life.

Detection of Hepatitis E Virus in Rabbits and Rabbit Meat from Slaughterhouses in Hebei Province of China

Background: Hepatitis E virus (HEV) is a zoonotic pathogen. HEV has been found to be widely prevalent in rabbits. Its isolates are classified into HEV-3, rabbit subgenotype (HEV-3ra). The routes of human infection with HEV-3ra remain unclear; however, foodborne transmission is possible when asymptomatically infected animals enter the food chain. The prevalence of HEV infection in slaughtered rabbits and the presence of HEV in rabbit meat were evaluated in this study. Materials and Methods: In three slaughterhouses in Hebei province, China, samples of rabbit blood were collected during the slaughter process, and muscle, liver, and cavity juice were collected from the rabbit carcasses. Anti-HEV antibody in serum samples was detected using enzyme-linked immunosorbent assay. HEV RNA was tested in all samples by reverse transcription nested PCR (RT-nested PCR). The final amplicons of RT-nested PCR were sequenced and phylogenetically analyzed. Results: Of the 459 serum samples, 50 [10.9%, 95% confidence interval (CI): 8.1-13.7] were positive for anti-HEV antibody, and 17 (3.7%, 95% CI: 2.0-5.4) were positive for HEV RNA. HEV RNA was detected in 7 of 60 liver samples (11.7%, 95% CI: 3.3-20) and 2 cavity juice samples from semi-eviscerated carcasses, but was not detected in any muscle sample from either the eviscerated or semi-eviscerated carcasses. All the detected HEV strains belonged to HEV-3ra and related most closely with the rabbit HEV sequence previously reported in China. Conclusion: A portion of rabbits were in the viremia period of HEV infection at the slaughter age, resulting in the possibility of HEV carriage by rabbit carcass, particularly semi-eviscerated carcass containing liver. These findings suggest a potential risk of HEV transmission from raw rabbit products entering the food chain, whereas the presence of HEV appeared to be lower in the eviscerated carcass than in the semi-eviscerated carcass.

Infection Dynamics and Genomic Mutations of Hepatitis E Virus in Naturally Infected Pigs on a Farrow-to-Finish Farm in Japan: A Survey from 2012 to 2021

Hepatitis E virus (HEV) causes acute or chronic hepatitis in humans. Pigs are the primary reservoir for zoonotic HEV genotypes 3 and 4 worldwide. This study investigated the infection dynamics and genomic mutations of HEV in domestic pigs on a farrow-to-finish pig farm in Japan between 2012 and 2021. A high prevalence of anti-HEV IgG antibodies was noted among pigs on this farm in 2012, when the survey started, and persisted for at least nine years. During 2012-2021, HEV RNA was detected in both serum and fecal samples, indicating active viral replication. Environmental samples, including slurry samples in manure pits, feces on the floor, floor and wall swabs in pens, and dust samples, also tested positive for HEV RNA, suggesting potential sources of infection within the farm environment. Indeed, pigs raised in HEV-contaminated houses had a higher rate of HEV infection than those in an HEV-free house. All 104 HEV strains belonged to subgenotype 3b, showing a gradual decrease in nucleotide identities over time. The 2012 (swEJM1201802S) and 2021 (swEJM2100729F) HEV strains shared 97.9% sequence identity over the entire genome. Importantly, the swEJM2100729F strain efficiently propagated in human hepatoma cells, demonstrating its infectivity. These findings contribute to our understanding of the prevalence, transmission dynamics, and genetic characteristics of HEV in domestic pigs, emphasizing the potential risks associated with HEV infections and are crucial for developing effective strategies to mitigate the risk of HEV infection in both animals and humans.

Laboratory Diagnosis of HEV Infection

Serological and nucleic acid tests for detecting hepatitis E virus (HEV) have been developed for both epidemiologic and diagnostic purposes. The laboratory diagnosis of HEV infection depends on the detection of HEV antigen or HEV RNA in the blood, stool, and other body fluids, and serum antibodies against HEV (immunoglobulin [Ig]A, IgM, and IgG). Anti-HEV IgM antibodies and low avidity IgG can be detected during the acute phase of the illness and can last approximately 12 months, representing primary infection, whereas anti-HEV IgG antibodies can last more than several years, representing remote exposure. Thus, the diagnosis of acute infection is based on the presence of anti-HEV IgM, low avidity IgG, HEV antigen, and HEV RNA, while epidemiological investigations are mainly based on anti-HEV IgG. Although significant progress has been made in developing and optimizing different formats of HEV assays, improving their sensitivity and specificity, there are many shortcomings and challenges in inter-assay concordance, validation, and standardization. This article reviews the current knowledge on the diagnosis of HEV infection, including the most common available laboratory diagnostic techniques.

Serological Evidence of Hepatitis E Virus Circulation Among Reindeer and Reindeer Herders

Various deer species are infected with hepatitis E virus (HEV) and may be a source of zoonotic infection for humans. So far, HEV has not been isolated from reindeer and the role of this domesticated deer species in HEV transmission is unknown. We tested serum samples from 191 reindeer (Rangifer tarandus) and 86 adult reindeer herders from the circumpolar regions of Yakutia (Russian Federation) for anti-HEV and HEV RNA. Anti-HEV IgG prevalence was 12.0% (95% confidence interval [95% CI]: 8.1-17.5) in reindeer and 4.7% (95% CI: 1.5-11.7) in reindeer herders. The latter was similar to the positivity rate observed in adult residents of the city of Yakutsk, the capital of Yakutia, who do not have routine contact with reindeer (3.7% [19/519, 95% CI: 2.3-5.7]). No samples positive for HEV RNA were identified. The study provides evidence of HEV circulation in reindeer. Nevertheless, the low seroprevalence in reindeer herders indicate a low risk of zoonotic HEV infection.

Infection dynamics and persistence of hepatitis E virus on pig farms - a review

Background

Hepatitis E virus (HEV) genotype 3 and 4 is a zoonosis that causes hepatitis in humans. Humans can become infected by consumption of pork or contact with pigs. Pigs are the main reservoir of the virus worldwide and the virus is present on most pig farms.

Main body

Though HEV is present on most farms, the proportion of infected pigs at slaughter and thus the level of exposure to consumers differs between farms and countries. Understanding the cause of that difference is necessary to install effective measures to lower HEV in pigs at slaughter. Here, HEV studies are reviewed that include infection dynamics of HEV in pigs and on farms, risk factors for HEV farm prevalence, and that describe mechanisms and sources that could generate persistence on farms. Most pigs become infected after maternal immunity has waned, at the end of the nursing or beginning of the fattening phase. Risk factors increasing the likelihood of a high farm prevalence or proportion of actively infected slaughter pigs comprise of factors such as farm demographics, internal and external biosecurity and immunomodulating coinfections. On-farm persistence of HEV is plausible, because of a high transmission rate and a constant influx of susceptible pigs. Environmental sources of HEV that enhance persistence are contaminated manure storages, water and fomites.

Conclusion

As HEV is persistently present on most pig farms, current risk mitigation should focus on lowering transmission within farms, especially between farm compartments. Yet, one should be aware of the paradox of increasing the proportion of actively infected pigs at slaughter by reducing transmission insufficiently. Vaccination of pigs may aid HEV control in the future.

Pilot Investigation on the Presence of Anti-Hepatitis E Virus (HEV) Antibodies in Piglet Processing Fluids

Simple Summary

Domestic and wild pigs are the main Hepatitis E virus (HEV) zoonotic reservoirs. Identifying HEV-positive pig farms is important to implement surveillance programs for this emerging zoonotic agent. The aim of this study was to evaluate the use of serosanguineous fluids obtained as part of castration practice (processing fluids (PFs)) to detect anti-HEV antibodies. Ninety-five paired serum and PF samples were collected from newborn piglets of 29 different litters and tested with a commercial ELISA kit. A significant positive correlation (Spearman’s rho: 0.600; p < 0.01) was found between the signal-to-cutoff (S/Co) ratio of anti-HEV antibodies in serum and PF samples. In 26 out of 29 litters (89.7%), there was at least one positive piglet in the serum. Sixteen litters out of 29 (55.2%) were also positive in PFs. The detection of anti-HEV maternal-derived antibodies in PFs confirms a past exposure of sows to the virus. PF may represent a rapid, noninvasive and economical tool to identify HEV-positive farms.

Abstract

Identifying Hepatitis E virus (HEV)-positive pig farms is important to implement surveillance programs for this emerging zoonotic agent. The aim of this study was to evaluate the use of serosanguineous fluids obtained as part of castration practice (processing fluids (PFs)) to detect anti-HEV antibodies in newborn piglets. Ninety-five paired serum and PF samples were collected from piglets of 29 different litters and tested with a commercial ELISA kit. A significant positive correlation (Spearman’s rho: 0.600; p < 0.01) was found between anti-HEV antibodies in serum and PF samples. In 26 out of 29 litters (89.7%), there was at least one positive piglet in the serum. Sixteen litters out of 29 (55.2%) were also positive in PFs. To simulate the use of PF as pooled samples, the limit of detection of the ELISA was assessed mixing the PF sample with strong, medium, medium-weak and weak ELISA titres with 3, 4, 5 and 6 negative PF samples. Our results suggest that it is still possible to identify a positive PF pool when at least one individual PF sample with medium or strong antibody levels is mixed with 5 or 6 individual negative PF samples. The detection of anti-HEV maternal-derived antibodies in PF confirms a past exposure of sows to the virus. PF may represent a rapid, noninvasive and economical tool to identify HEV-positive 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.

Hepatitis E virus strains infecting Swedish domestic pigs are unique for each pig farm and remain in the farm for at least 2 years

Hepatitis E virus (HEV) genotype 3 (HEV3) is distributed globally and infects both humans and animals, mainly domestic pigs and wild boars, which are the major reservoirs. In this study, the prevalence of HEV among Swedish pigs was investigated by HEV RNA analysis in 363 faecal samples from 3-month-old piglets sampled twice (2013 and 2014) in 30 Swedish pig farms. Four different types of farms were investigated; organic, conventional closed (keeping the sow), satellites in a sow pool (conventional farms sharing sows) and conventional non-closed farms (purchasing gilts). More than two-thirds (77%) of the farms had HEV-infected pigs. HEV RNA was found in faeces from 79 pigs (22%). Partial ORF1 could be sequenced in 46 strains. Phylogenetic analysis revealed a unique HEV3 strain for each farm. Strains sampled more than a year apart from the same farm were closely related, indicating that the same HEV strain is present for several years on the farm. Despite that only 4% of the Swedish pig farms were investigated, two farms had strains similar to those from humans, another had strains similar to wild boar HEV. The uniqueness of strains from each farm indicates a possibility to identify a source of infection down to farm level. This knowledge may be used by the farms to investigate the effectiveness of good hygiene routines to reduce the amount of HEV and thus the infection risk in the farm, and for Swedish public health authorities to identify cases of HEV transmissions from consumption of uncooked pork.

Hepatitis E virus: zoonotic and foodborne transmission in developed countries

Hepatitis E virus (HEV), together with hepatitis A virus, transmits via the fecal–oral route. The number of domestic hepatitis E cases among Europeans has grown alarmingly during the past 5 years. Surveillance studies suggest that the number of foodborne HEV infections is increasing most rapidly. Zoonotic HEV genotype HEV-3 is prevalent among pigs and wild boars in Europe and many developed countries, whereas zoonotic genotype HEV-4 is more common in pigs in some Asian countries. This review presents the most recent data about possible foodborne transmission of HEV via pigs and other production animals and about the presence of HEV in high-risk foods, such as ready-to-eat meat products. Possible solutions about how to tackle this problem are discussed here.

Recent knowledge on hepatitis E virus in Suidae reservoirs and transmission routes to human

Hepatitis E virus (HEV) causes self-limiting acute hepatitis in humans that can eventually result in acute liver failures or progress to chronic infections. While in tropical and sub-tropical areas, HEV infections are associated with important waterborne epidemics, in Northern countries, HEV infections are autochthonous with a zoonotic origin. In the past decade, it has become clear that certain HEV genotypes are zoonotic and that swine, and more generally Suidae, are the main reservoir. Zoonotic transmissions of the virus may occur via direct contact with infected pigs, wild boars or consumption of contaminated meat. This review describes the current knowledge on domestic and wild Suidae as reservoirs of HEV and the evidence of the different routes of HEV transmission between these animals and humans.

A comprehensive study of hepatitis E virus infection in pigs entering a slaughterhouse in Slovenia

Hepatitis E is a zoonotic viral disease of pigs with increasing public health concern in industrialized countries. Presented broad study of hepatitis E virus (HEV) presence in pigs in Slovenia is the first attempt to overview the HEV situation in pigs entering a slaughterhouse and, further, to analyse the possibility of HEV entering into the food supply chain. 2433 samples from 811 clinically healthy pigs were collected at four slaughterhouses in Slovenia. Sampling covered three different age groups of pigs and three different types of samples (faeces, bile and liver) important for tracing HEV in a pig population. In addition, 63 swab samples were collected systematically from three different sites on the slaughter line, as well as 22 samples of minced meat and 30 bratwurst samples. All the samples were screened for the presence of HEV nucleic acids by specific real-time RT-PCR assay. In the group of three month old pigs 13.7% of faeces, 13.0% of bile and 2.1% of liver samples were HEV positive. In the group of six months old pigs only 0.25% of liver and 0.25% of bile samples were positive. In the category of sows, no positive samples were found. Two out of 63 swab samples collected on the slaughter line were HEV positive. All tested samples of minced meat and bratwurst were negative. The phylogenetic analysis of 50 HEV positive samples, with comparison of 366 nucleotides in ORF1 region, revealed high diversity of identified strains of HEV in pigs, belonging into subtypes 3a, 3b, 3c and 3e.

Laboratory Diagnosis of HEV Infection

Serological and nucleic acid tests for detecting hepatitis E virus (HEV) have been developed for both epidemiologic and diagnostic purposes. The laboratory diagnosis of HEV infection depends on the detection of HEV antigen, HEV RNA, and serum antibodies against HEV (immunoglobulin [Ig]A, IgM, and IgG). Anti-HEV IgM antibodies can be detected during the acute phase of the illness and can last approximately 4 or 5 months, representing recent exposure, whereas anti-HEV IgG antibodies can last more than 10 years, representing remote exposure. Thus, the diagnosis of acute infection is based on the presence of anti-HEV IgM, HEV antigen, and HEV RNA, while epidemiological investigations are mainly based on anti-HEV IgG. Although significant progress has been made in developing and optimizing different formats of HEV assays, improving their sensitivity and specificity, there are many shortcomings and challenges in inter-assay concordance, validation, and standardization. This article reviews the current knowledge on the diagnosis of HEV infection, including the most common available laboratory diagnostic techniques.

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 infection in two different regions of Indonesia with identification of swine HEV genotype 3

Hepatitis E is an emerging disease with a high incidence globally. Few data are available on hepatitis E virus (HEV) infection in Indonesia. To obtain molecular information on HEV infection in two regions of Indonesia with different customs and swine breeding conditions, serum samples from 137 swine farm workers, 100 blood donors and 100 swine (27 fecal samples also obtained) in Yogyakarta (Central Java) and from 12 and 64 swine farm workers, 42 and 135 local residents and 89 and 119 swine in Tulungagung (East Java) and Mengwi (Bali), respectively, from our previous study, were compared.Serological tests for anti‐HEV antibodies by ELISA, HEV‐RNA detection by RT‐PCR and phylogenetic analysis were performed. The total prevalence of anti‐HEV antibodies in humans was higher in Bali(11.6%) than in Java (5.1%; P=0.015). No significant differences in anti‐HEV prevalence among swine farm workers and local residents in Java were found. The finding of swine HEV genotype 3 in specimens from Yogyakarta and genotype 4 from Tulungagung and Bali is somewhat different from other reports.We suggest other factors in addition to close contact with swine might play an important role in HEV transmission of non‐endemic/related custom groups. To the best of our knowledge, this is the first report on swine HEV genotype 3 in Indonesia.

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.

Hepatitis E virus in young pigs in Finland and characterization of the isolated partial genomic sequences of genotype 3 HEV

Hepatitis E virus (HEV) infections occur in swine worldwide. The porcine infection is usually subclinical, but HEV genotypes 3 and 4 are zoonotic agents that cause sporadic, indigenous human cases of hepatitis E. The aims of this study were to investigate the occurrence and dynamics of HEV infections in young pigs by analyzing a total of 273 fecal samples collected from six farrowing farms, to genetically characterize the HEV isolates obtained, and to examine the phylogenetic relationships of HEV isolates occurring at different swine farms in Finland. Fecal shedding of HEV of individual piglets was followed at two farms that were selected from five farms identified as HEV RNA positive. Excretion of HEV was detected in 87.5% of the piglets during the survey. Piglets contracted primary HEV infection 3-8 weeks after weaning, and at the time they were transferred to fattening farms, practically all (96.6%) of the pigs with a sample available at this occasion still excreted the virus. According to phylogenetic analysis, all HEV isolates obtained belonged to HEV genotype 3, subtype e, and a separate, farm-specific isolate originated from 10 of 11 farms examined. The results of our study show that HEV infections are highly common in young pigs, and HEV RNA-positive pigs enable HEV transmission from farrowing to fattening farms, creating a possible risk of infection for pig handlers, and that genetic variations in HEVs originating from different farms occur.

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.

A longitudinal study revealing hepatitis E virus infection and transmission at a swine test station

Hepatitis E virus (HEV) is a zoonotic agent that causes acute hepatitis in humans, and infects several animal species, most importantly swine. In the current study, that presents the first evidence of HEV infections in pigs in Finland, genetic divergence and transmission of HEV was investigated among pigs at a swine test station at two occasions. In 2007, HEV RNA was found in 25% of pens, and 35% of 2-3 month-old pigs at the station. Three different isolates, comprising 13 sequences of HEV genotype 3 e that were imported from different farms were detected. In 2010, 39% of pigs were HEV RNA positive on weeks 1, 3, or 5 of a 3-month follow-up, and 11 sequences, all representing one of the isolates that was also present in 2007, were detected. The isolate was considered to be either re-introduced to, or to persist at the station, and it was transmitted between the pigs. The study sheds light on the rate and time of HEV transmission in swine, and describes the epidemiologic variability of HEV isolates over time.

Immune modulatory function of abundant immune-related microRNAs in microvesicles from bovine colostrum

Colostrum provides essential nutrients and immunologically active factors that are beneficial to newborns. Our previous work demonstrated that milk contains large amounts of miRNA that is largely stored in milk-derived microvesicles (MVs). In the present study, we found that the MVs from colostrum contain significantly higher levels of several immune-related miRNAs. We hypothesized that the colostrum MVs may transfer the immune-related miRNAs into cells, which contribute to its immune modulatory feature. We isolated colostrum MVs by ultracentrifugation and demonstrated several immune modulation features associated with miRNAs. We also provide evidence that the physical structure of milk-derived MVs is essential for transfer miRNAs and following immune modulation effect. Moreover, we found that colostrum powder-derived MVs also contains higher levels of immune-related miRNAs that display similar immune modulation effects. Taken together, these results show that MV-containing immunerelated miRNAs may be a novel mechanism by which colostrum modulates body immune response.

Serological evidence for a hepatitis e virus-related agent in goats in the United States

Hepatitis E virus (HEV) causes an important public health disease in many developing countries and is also endemic in some industrialized countries. In addition to humans, strains of HEV have been genetically identified from pig, chicken, rat, mongoose, deer, rabbit and fish. While the genotypes 1 and 2 HEV are restricted to humans, the genotypes 3 and 4 HEV are zoonotic and infect humans and other animal species. As a part of our ongoing efforts to search for potential animal reservoirs for HEV, we tested goats from Virginia for evidence of HEV infection and showed that 16% (13/80) of goat sera from Virginia herds were positive for IgG anti-HEV. Importantly, we demonstrated that neutralizing antibodies to HEV were present in selected IgG anti-HEV positive goat sera. Subsequently, in an attempt to genetically identify the HEV-related agent from goats, we conducted a prospective study in a closed goat herd with known anti-HEV seropositivity and monitored a total of 11 kids from the time of birth until 14 weeks of age for evidence of HEV infection. Seroconversion to IgG anti-HEV was detected in seven of the 11 kids, although repeated attempts to detect HEV RNA by a broad-spectrum nested RT-PCR from the faecal and serum samples of the goats that had seroconverted were unsuccessful. In addition, we also attempted to experimentally infect laboratory goats with three well-characterized mammalian strains of HEV but with no success. The results indicate that a HEV-related agent is circulating and maintained in the goat population in Virginia and that the goat HEV is likely genetically very divergent from the known HEV strains.