岡本 宏明

Previous studies have emphasized the necessity of surveillance and control measures for hepatitis E virus (HEV) infection in wild boars, an important reservoir of HEV. To assess the current situation of HEV infection in wild boars in Japan, this study investigated the prevalence and genetic diversity of HEV among wild boars captured in 16 prefectures of Japan during 2018-2023. Serum samples from 968 wild boars were examined for anti-HEV IgG antibodies and HEV RNA. The prevalence of anti-HEV IgG varied geographically from 0 % to 35.0 %. HEV RNA was detected in 3.6 % of boars, with prevalence varying by prefecture from 0 % to 22.2 %. Genotype 3 was the most prevalent genotype (91.9 %), followed by genotype 4 (5.4 %), with one strain closely related to genotype 6. The prevalence of HEV infection among wild boars decreased from 2018/2019 to 2022/2023 with significant declines in levels of anti-HEV IgG antibodies (14.5 % vs. 6.2 %, P < 0.0001) and HEV RNA (7.6 % vs. 1.5 %, P < 0.0001). Regional analysis showed varying trends, with no HEV RNA-positive boars found in several regions in recent years. A plausible factor contributing to the decline in HEV infection is the application of countermeasures, including installing fences to prevent intrusion into pig farms, implemented in response to the emergence of classical swine fever virus (CSFV) infection in wild boars and domestic pigs, with incidents reported annually since 2018. Further investigation is warranted to explore the association between countermeasures to CSFV infection and the decrease in HEV infection among wild boars.

Spontaneous reactivation of the Hepatitis B virus (HBV) is rare in individuals with previously resolved infections. This report presents the case of a 71 year-old Japanese woman who experienced HBV reactivation without any prior immunosuppressive therapy or chemotherapy. Before the onset of liver injury, the patient was negative for hepatitis B surface antigen (HBsAg) but positive for hepatitis B surface antibody. She subsequently developed liver injury, with the reappearance of HBsAg and HBV DNA. The patient was successfully treated with tenofovir alafenamide, and prednisolone. Full-genome sequencing of HBV revealed subgenotype B1 without hepatitis B e-negative mutations in the precore and core promoter regions and 12 amino acid alterations in the pre-S1/S, P, and X genes. Notably, the S gene mutations D144A and K160N, which alter the antigenicity of HBsAg and potentially contribute to its reactivation, were identified. This case emphasizes the importance of vigilance for spontaneous reactivation of resolved HBV, highlighting the need for comprehensive genomic analysis to understand the associated virological intricacies.

Hepatitis E virus (HEV) genotypes 3 and 4 are zoonotic strains that are primarily transmitted through the consumption of undercooked pork or game meat. They also cause asymptomatic infections, acute hepatitis, acute-on-chronic liver failure, chronic hepatitis, and extrahepatic manifestations. Here, we report a man in his 80s who had chronic hepatitis B, took entecavir for it, and presented with higher levels of alanine aminotransferase (ALT) and jaundice. An abdominal computed tomography scan revealed choledocholithiasis with cholecystolithiasis. Although endoscopic papillary balloon dilatation was performed for the removal of a common bile duct stone, the abnormal liver function tests, including jaundice, were prolonged. After other viral hepatitis and other causes of the liver injury were ruled out, as his serum was positive for immunoglobulin A anti-HEV and HEV genotype 3b RNA, we diagnosed him as having acute hepatitis E. In this case, with chronic hepatitis B and a common bile duct stone, the prolonged abnormal results for the liver function tests seemed to be caused by HEV infection. In conclusion, in cases with high ALT levels after removing choledocholithiasis, other factors, including HEV infection, should be considered to determine the cause of abnormal liver function test results. The further examination of hepatitis D virus infection and high ALT levels may be needed in HBV-infected individuals.