Detection of hepatitis E virus RNA from pig bile collected at a slaughterhouse in Japan

Abstract

Hepatitis E virus (HEV) is a zoonotic pathogen that circulates mainly between pigs and humans. In Japan, the number of confirmed HEV cases has increased over the past decade, with the majority reported as domestic HEV infections. HEV-infected pork products may be associated with this increase, but there is limited information on HEV in pork in Japanese markets. From February to March 2020, gallbladders were collected from 200 slaughtered pigs shipped from 14 farms and were surveyed to detect HEV RNA in bile using reverse transcription quantitative polymerase chain reaction. The samples were then sequenced and genotyped. Twenty pigs were positive for HEV ribonucleic acid, and seven samples had Ct values of less than 30. Among these 20 pigs, virus strains from 14 pigs were determined as genotype 3. This report indicated that HEV-contaminated pork liver was shipped to consumer markets and demonstrated the importance of detection of HEV in meat ready for shipment.

Keywords: hepatitis E virus; liver; pig, bile; slaughterhouse.

Figure 1.. Annual numbers of confirmed hepatitis E cases in Japan between 2011 and 2020. Data available from Infectious Diseases Weekly Report (https://www.niid.go.jp/niid/ja/ydata/10411-report-ja2020-20.html) released from National Institute of Infectious Diseases. For 2020, the data were aggregated until October 30.

Figure 2.. Genotype analysis of 14 virus strains was conducted using GENETYX ver14 software with the UPGMA method based on the Kimura's 2 parameter model. These strains belonged to genotype 3 and have been labeled in the phylogenetic tree as ‘farm number – pig number’.