Hepatitis E Virus in Pork Production Chain in Czech Republic, Italy, and Spain, 2010

Ilaria Di Bartolo¹, Marta Diez-Valcarce¹, Petra Vasickova¹, Petr Kralik, Marta Hernandez, Giorgia Angeloni, Fabio Ostanello, Martijn Bouwknegt, David Rodríguez-Lázaro, Ivo Pavlik, and Franco Maria Ruggeri

Author affiliations: Istituto Superiore di Sanità, Rome, Italy (I. Di Bartolo, G. Angeloni, F.M. Ruggeri); Instituto Tecnológico Agrario de Castilla y León, Junta de Castilla y León Valladolid, Spain (M. Diez-Valcarce, M. Hernandez, D. Rodríguez-Lázaro); Veterinary Research Institute, Brno, Czech Republic (P. Vasickova, P. Kralik, I. Pavlik); University of Bologna, Bologna, Italy (F. Ostanello); and National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands (M. Bouwknegt)

Abstract

We evaluated the prevalence of hepatitis E virus (HEV) in the pork production chain in Czech Republic, Italy, and Spain during 2010. A total of 337 fecal, liver, and meat samples from animals at slaughterhouses were tested for HEV by real-time quantitative PCR. Overall, HEV was higher in Italy (53%) and Spain (39%) than in Czech Republic (7.5%). HEV was detected most frequently in feces in Italy (41%) and Spain (39%) and in liver (5%) and meat (2.5%) in Czech Republic. Of 313 sausages sampled at processing and point of sale, HEV was detected only in Spain (6%). HEV sequencing confirmed only g3 HEV strains. Indicator virus (porcine adenovirus) was ubiquitous in fecal samples and absent in liver samples and was detected in 1 slaughterhouse meat sample. At point of sale, we found porcine adenovirus in sausages (1%–2%). The possible dissemination of HEV and other fecal viruses through pork production demands containment measures.

Human hepatitis E is endemic worldwide, particularly in Asia, where large waterborne outbreaks have been reported (1). Seroprevalence of hepatitis E virus (HEV) is >60% in rural southern People’s Republic of China (2) and 4%–10% in western Europe (3) and the United States (4). In these areas, hepatitis E occurs mostly as sporadic cases (5–7), but epidemics also have been described (8). Most cases in Europe have been linked to genotype 1 (g1) virus and associated with travel to g1-endemic areas. However, autochthonous human infections are increasing in Europe and in other industrialized countries (5,6,9). Of the 4 genotypes affecting humans, genotype 3 (g3) is the main HEV genotype also circulating among pigs in Europe (10) and human infections are observed sporadically worldwide (11,12).
Several reports indicate that HEV can be transmitted through zoonotic and foodborne pathways, including through consumption of raw and undercooked liver, meat, or sausages from domestic pigs, wild boar, and deer (8,13,14). Several investigations have shown that farmed domestic pigs are widely infected with and shed g3 HEV in Europe. Studies conducted in Spain (8,13,14), Italy (15), and France (16) have detected HEV genomic RNA in livers of pigs of slaughtering age, indicating that HEV-contaminated food might reach supermarkets (17). In butcher shops in the Netherlands (18) and Germany (19), ≈6.5% and ≈4%, respectively, of pork livers contained HEV, which raises concern about the potential for direct transmission through contact with or consumption of contaminated food.
Despite the large widespread distribution of HEV-shedding pigs and the possible role of farmed pigs as the main virus reservoir, the number of human hepatitis E cases in Europe remains low, suggesting inefficient virus transmission or lower pathogenicity of swine g3 strains than of g1 strains for humans. Because g3 HEV is common in pigs but rare in humans, humans are postulated to not be a main host for g3 virus replication (11,20). Nonetheless, a possibly large underestimation of HEV spread in humans cannot be excluded because of asymptomatic cases, inadequate diagnostics, and scarce medical attention (21). Mansuy et al. suggested inadequacy of previous diagnostic methods and recently found unprecedentedly high HEV seroprevalence among blood donors in France (22).
Relatively few studies of foodborne human hepatitis E are available (8,21,23), making evaluation of HEV-associated risks difficult. Investigation of HEV throughout the pork production chain from farm to point of sale is needed to highlight areas of risk and proper control. A recent report from European Food Safety Authority biohazard experts (24) underscored an urgent need for integrated studies on HEV circulation, performing farm-to-table integrated risk assessment. For other foodborne pathogens, such studies comprise quantitative microbial risk assessment on the basis of exposure and dose-response models (25). Unfortunately, for HEV, quantitative approaches are hardly accessible because of the absence of reliable cell culture systems for viral infectivity titration.
We aimed to assess HEV prevalence in the pork production chain from slaughterhouse to point of sale in Czech Republic, Italy, and Spain during 2010 in the framework of the FP7 VITAL (Integrated Monitoring and Control of Foodborne Viruses in European Food Supply Chains) project (www.eurovital.org

). This systematic multicountry investigation of domestic swine HEV was conducted by using standardized molecular approaches, including reverse transcription quantitative PCR (RT-qPCR) detection, process, and internal amplification controls (IACs) and proper fecal viral indicators (porcine adenovirus [PAdV]).