Screening of Swiss Pig Herds for Hepatitis E Virus: A Pilot Study

SIMPLE SUMMARY: Hepatitis E is a viral disease found in humans worldwide. The hepatitis E virus (HEV) is also found in various animals, with pigs as the main reservoir. A transmission of the zoonotic genotype 3 to humans is possible via direct contact with infected animals or through the consumption of raw or undercooked meat. A good knowledge of the genetic diversity of the virus in pigs is needed to prevent future transmissions by tracing chains of infections. Thus, this study aimed at developing a practical and easy to use screening tool for pig herds and gaining first experiences with it. Sock swabs turned out to be the method of choice and were used to test 138 Swiss pig herds for HEV. In positive cases the virus was further characterized. Of the 138 farms tested, 81 were HEV positive (58.8%) and most viral sequences belonged to a distinct cluster within subtype 3h that was also commonly found in Swiss patients infected with HEV. These data showed that sock swabs are useful for HEV screening in pig herds, that HEV is frequent in Swiss pig herds, and that the same subtype of virus is found in Swiss pig farms and human patients. ABSTRACT: Hepatitis E virus (HEV) is an important cause of acute hepatitis in humans worldwide. In industrialised countries, most infections are caused by the zoonotic genotype 3. The main reservoir was found in pigs, with fattening pigs as the main shedders. The aim of this study was to establish a screening tool to detect HEV in pig farms. HEV-positive samples were sequenced using Sanger sequencing. First, different sample materials, including floor swabs, slurry, dust swabs and faeces were tested for HEV. Floor swabs turned out to give the best results and, in the form of sock swabs, were used for the screening of Swiss pig herds. A total of 138 pig farms were tested, with a focus on fattening pigs. Overall, 81 farms (58.8%) were HEV positive. Most sequences belonged to subtype 3h, in which they formed a specific cluster (Swiss cluster). In addition, subtype 3l and two unassigned sequences were detected. As a conclusion, sock swabs were found to be a helpful tool to screen pig herds for HEV and establish a sequence collection that may enable molecular epidemiology and support outbreak investigation and prevention.