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

High circulation of hepatitis E virus (HEV) in pigs from the central region of Argentina without evidence of virus occurrence in pork meat and derived products

Hepatitis E virus (HEV) is an emerging cause of viral hepatitis and pigs are considered a reservoir for the virus. HEV genotype 3 (HEV-3) has been reported in pigs, environmental matrices, and sporadic human cases in Argentina. We aimed to investigate HEV circulation in pigs from central Argentina and to assess the virus presence in pork meat and food products. Four types of samples obtained or derived from pigs collected in Córdoba province (Argentina) between 2019 and 2022, were tested: 276 serum samples were analyzed for anti-HEV antibody detection; stool (n = 20), pork meat (n = 71), and salami (n = 76) samples were studied for RNA-HEV detection, followed by sequencing and phylogenetic analyses. The positivity rate for anti-HEV antibodies was 80.1% (221/276). Eleven fecal samples (11/20) tested positive for RNA-HEV, from animals under 120 days of age. Three samples could be sequenced, and phylogenetic analyses revealed that they belonged to HEV-3 clade abchijklm, clustering close to strains previously detected in wastewater from Córdoba. None of the muscle meat or salami samples tested positive. A high HEV circulation in pigs was found, showing that these animals may play a significant role in the viral maintenance in the region, becoming a potential risk to the exposed population. Despite not detecting RNA-HEV in pork meat and salami in our study, we cannot rule out the possibility of foodborne transmission in Córdoba province.

Tracing the History of Hepatitis E Virus Infection in Mexico: From the Enigmatic Genotype 2 to the Current Disease Situation

Hepatitis E virus (HEV) is the major cause of acute viral hepatitis worldwide. This virus is responsible for waterborne outbreaks in low-income countries and zoonosis transmission in industrialized regions. Initially, considered self-limiting, HEV may also lead to chronic disease, and evidence supports that infection can be considered a systemic disease. In the late 1980s, Mexico became a hot spot in the study of HEV due to one of the first virus outbreaks in Latin America related to enterically transmitted viral non-A, non-B hepatitis. Viral stool particles recovered from Mexican viral hepatitis outbreaks represented the first identification of HEV genotype (Gt) 2 (Gt2) in the world. No new findings of HEV-Gt2 have been reported in the country, whereas this genotype has been found in countries on the African continent. Recent investigations in Mexico have identified other strains (HEV-Gt1 and -Gt3) and a high frequency of anti-HEV antibodies in animal and human populations. Herein, the potential reasons for the disappearance of HEV-Gt2 in Mexico and the advances in the study of HEV in the country are discussed along with challenges in studying this neglected pathogen. These pieces of information are expected to contribute to disease control in the entire Latin American region.

Study of Animal Mixing and the Dynamics of Hepatitis E Virus Infection on a Farrow-to-Finish Pig Farm

In Europe, swine are a livestock reservoir for Hepatitis E virus genotype 3 (HEV-3). Consumption of food containing HEV-3 can cause zoonotic human infection, though risk is reduced by heat treatment. Implementing controls that limit infection in slaughter pigs may further reduce foodborne transmission risk but knowledge of infection dynamics on commercial farms is limited. This study addressed this knowledge gap and in particular investigated the influence of group mixing. Faeces were collected from grower (n = 212) and fattener (n = 262) pigs on a farrow-to-finish farm on four occasions. HEV RNA was detected on all occasions, and prevalence was higher in growers (85.8%) than fatteners (26.0%; p < 0.001). HEV-positive samples were also collected from the wider farm environment (n = 67; 64.7% prevalence), indicating potential sources for HEV re-circulation within the herd. Timing of infection in a cohort was also investigated. HEV was absent from all piglet faeces (n = 98) and first detected at weaner stage (25.7% prevalence), but only in groups weaned earlier or comprising pigs from many different litters. Farrowing sow faeces (n = 75) were HEV-negative but antibodies were detected in blood from two sows. Results suggest that multiple factors influence HEV infection dynamics on pig farms, and potential foci for further study into practical control solutions are highlighted.

Hepatitis E virus infection and waste pickers: A case-control seroprevalence study

Whether waste pickers are a risk group for hepatitis E virus (HEV) infection is largely unknown. This study aimed to determine the association between HEV exposure and the occupation of waste pickers and the work characteristics of waste pickers. An age-and gender-matched case-control seroprevalence study of 86 waste pickers and 86 control subjects of the general population was performed. We determined anti-HEV IgG antibodies in sera of cases and controls using a commercially available enzyme-linked immunoassay. The McNemar's test was used to assess the association between HEV seropositivity and the occupation of waste picker. The association between HEV seropositivity and work characteristics of waste pickers was assessed by bivariate and logistic regression analyses. Anti-HEV IgG antibodies were detected in 14 (16.3%) of the 86 waste pickers and in 8 (9.3%) of the 86 control subjects (McNemar's pair test: odds ratio (OR) = 13.0; 95% confidence interval (CI): 0.73-230.77; p = .02). Bivariate analysis showed that HEV exposure was associated with an ill status (p = .01) and reflexes impairment (p = .009). Logistic regression analysis showed that HEV seropositivity was associated with increasing age (OR = 6.52; 95% CI: 1.95-21.78; p = .002) and raising pigs (OR = 12.01; 95% CI: 1.48-97.26; p = .02). This is the first age- and gender-matched case-control study on the association between HEV infection and the occupation of waste picker. Waste pickers represent a risk group for HEV infection. Factors associated with HEV seropositivity found in this study may help in the design of optimal planning to avoid HEV infection.

Hepatitis E Virus Infection and Butchers: A Case-Control Seroprevalence Study

Background

Very few case-control studies to assess the risk of hepatitis E virus (HEV) infection in meat workers have been published. Therefore, we sought to determine: 1) the association of HEV IgG seropositivity and the occupation of butcher; and 2) the sociodemographic, work, clinical and behavioral characteristics of butchers associated with HEV exposure.

Methods

We performed a case-control seroprevalence study of 101 butchers (mean age: 38.50 ± 12.52 years) and 101 age-, gender- and residence-matched control subjects of the general population. Anti-HEV IgG antibodies were determined using a commercially available enzyme-linked immunoassay. Bivariate and regression analyses were used to assess the association between HEV seropositivity and characteristics of butchers.

Results

Anti-HEV IgG antibodies were found in 18 (17.8%) of the 101 butchers and in 14 (13.9%) of the 101 control subjects (odds ratio (OR): 1.34; 95% confidence interval (CI): 0.63 - 2.88; P = 0.44). Stratification by sex, age and area of residence (rural or urban) in cases and controls showed similar seroprevalences of HEV infection among groups. Bivariate analysis showed that HEV seroprevalence was associated with low education (up to 6 years), work place, seniority, eating while working, a history of raising farm animals and national trips. However, further analysis by logistic regression showed that only the variable of national trips was associated with HEV exposure (OR: 5.38; 95% CI: 1.02 - 28.16; P = 0.04). Concerning clinical characteristics of butchers, no association between HEV exposure and health status, history of surgery or blood transfusion was found.

Conclusions

Results from this first age-, gender- and residence-matched serosurvey of HEV infection in butchers in Mexico suggest that this population group does not have a higher risk for HEV infection than people from the general population. However, further studies to confirm the lack of association between HEV infection and the occupation of butcher are needed.