Hepatitis E Virus (HEV) in Heavy Pigs in Slaughterhouses of Northern Italy: Investigation of Seroprevalence, Viraemia, and Faecal Shedding

SIMPLE SUMMARY: Hepatitis E virus (HEV) is spread worldwide among both humans and animals. In humans, the diseases can be asymptomatic, but it can also lead to chronic hepatitis, especially in immunocompromised patients. In the European Union, most human cases are foodborne and caused by the zoonotic genotypes HEV-3 and HEV-4. Pigs and wild boars serve as the main reservoirs for these zoonotic genotypes, as they are frequently infected by the virus, which replicates in the liver and is released in their faeces. This study aimed to assess the presence of HEV in heavy pigs (>160 kg) in a large abattoir in Italy. Both 240 pooled faecal samples collected on 24 trucks after unloading pigs and 88 plasma samples collected individually were negative for HEV RNA. Only five pigs (1.9%) tested positive for IgM, a sign of recent infection. Conversely, a high seroprevalence of 89.2%, confirmed by detection of total anti-HEV antibodies, demonstrated the wide exposure of pigs to the virus. ABSTRACT: Hepatitis E virus (HEV) is considered an emerging threat in Europe, owing to the increased number of human cases and the widespread presence of the virus in pigs at farms. Most cases in industrialized countries are caused by the zoonotic HEV-3 genotype. The main transmission route of HEV-3 in Europe is foodborne, through consumption of raw or undercooked liver pork and wild boar meat. Pigs become susceptible to HEV infection after the loss of maternal immunity, and the majority of adult pigs test positive for IgG anti-HEV antibodies. Nonetheless, HEV-infected pigs in terms of liver, faeces, and rarely blood are identified at slaughterhouses. The present study aimed to investigate the prevalence of HEV-positive batches of Italian heavy pigs at slaughterhouses, assessing the presence of animals still shedding HEV upon their arrival at the slaughterhouse by sampling faeces collected from the floor of the trucks used for their transport. The occurrence of viraemic animals and the seroprevalence of anti-HEV antibodies were also assessed. The results obtained indicated the presence of anti-HEV IgM (1.9%), and a high seroprevalence of anti-HEV total antibodies (IgG, IgM, IgA; 89.2%, n = 260). HEV RNA was not detected in either plasma or faecal samples. Nevertheless, seropositive animals were identified in all eight batches investigated, confirming the widespread exposure of pigs to HEV at both individual and farm levels. Future studies are needed to assess the factors associated with the risk of HEV presence on farms, with the aim to prevent virus introduction and spread within farms, thereby eliminating the risk at slaughterhouse.