Hepatitis E virus: Monitoring for the evaluation of the prevalence of infection in Italian piggery and in the human population

Background: The hepatitis E virus (HEV) is a leading cause of acute hepatitis in developing countries and an emerging pathogen in Europe. In industrial countries viral genotypes 3 and 4 are found in swine, wild boar, deer and rabbits, and they are often associated with autochthonous cases suggesting the existence of zoonotic HEV infections. A putative involvement of undercooked pork and possible contact with infected animals represent routes of transmission to human beings. A monitoring plan was performed to evaluate the prevalence of HEV infection in humans and pigs of North-East of Italy to better investigate whether consumption of pork products and/or contact with pigs may represent a risk factor. Methods: During 2012-2014 period, serum samples were collected from 405 volunteers divided into two groups of people: a) workers in contact with swine (185); b) general population with different diets, omnivorous (108) and vegetarian (112). All sera samples were tested by ELISA to detect anti-HEV IgG/IgM antibodies. During the same time, 175 pig farms were sampled to detect at least one positive sample assuming a within-herd seroprevalence of 30%, 9 sera were collected and analyzed from each farm. Seropositive farms were surveyed for the presence of the virus by real time RT-PCR and eventually characterized by sequencing and phylogenetic analysis. Results: HEV seroprevalence in humans was significantly different among 2 groups (p<0.001): farmers showing the greatest prevalence (15.75%,95% CI:9.9-23.3) and general population the lowest (2.3%,95% CI:0.5-6.5). No significant differences were found between omnivorous and vegetarian subjects. Anti-HEV antibodies were detected in 64.8% (114/175,95% CI:58.2-72.7) of the pig farms, while viral RNA was identified in 24.8% (26/105) of the sampled farms. Phylogenetic analysis on the nucleotide sequences identifies distinct subtypes of the genotype 3 and one, belonging to genotype 4, with 100% sequence similarity to a human Italian strain. Conclusion: The survey confirmed a widespread of HEV in Italian pig herds; for the first time HEV4 was identified in the Italian swine population. Moreover, this data corroborate an increased risk of HEV transmission to farmers due to their professional exposure.