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

Abstract

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.

Genetic Diversity of Hepatitis E Virus Type 3 in Switzerland—From Stable to Table

“…This finding confirms a previous observation of 58.1% seroprevalence in Swiss pigs at slaughtering age sampled in 2006 and 2011 [ 23 ] and underpins the finding that most pigs will become infected relatively early in life and have already developed an immune response and cleared the virus at the slaughtering timepoint. Early slaughtering timepoint and late infection, e.g., due to prolonged protection by high levels of maternal antibodies, were shown to be risk factors for pigs to be HEV positive at slaughter [ 45 , 46 ]. Seroprevalence of slaughtering pigs in Europe ranges between 30–98% [ 12 ].…”

A Systematic Review on the Effectiveness of Pre-Harvest Meat Safety Interventions in Pig Herds to Control Salmonella and Other Foodborne Pathogens

“…However, none of these papers fulfilled the criteria for inclusion in this systematic review. According to Meester et al [ 75 ], pigs are the main reservoir of the HEV (genotypes 3 and 4) worldwide, and humans can become infected by consumption of pork or contact with pigs. As HEV is persistently present on most pig farms, current risk mitigation strategies should focus on lowering transmission within farms, especially between farm compartments.…”

Impfstoffe gegen Hepatitis E: Wo stehen wir?

“…einen chronischen Verlauf nehmen und hier zu den relevanten Erkrankungen führen. 1 Ein aktueller Forschungsansätze (diskutiert in Referenz [36]).…”

“…Durch Immunisierungsstrategien bei den Tieren kann eine Reduktion des Anteiles HEV-positiver Nahrungsmittel erzielt werden. Dieser Ansatz steht im Mittelpunkt – bislang jedoch weniger – aktueller Forschungsansätze (diskutiert in Referenz [ 36 ]).…”