A systematic review and meta-analysis of hepatitis E virus (HEV) in wild boars

This systematic review and meta-analysis summarize the available information on Hepatitis E virus (HEV) -specific antibody seroprevalence and HEV RNA prevalence in wild boar, one of the most abundant game species worldwide. A literature search (CAB Abstracts, Web of Science, Embase and Scopus) was performed to find relevant peer-reviewed works published during the period 1990-2020. A random-effect model was carried out to calculate the pooled HEV-specific antibody seroprevalence and HEV RNA prevalence estimates with 95% confidence intervals, and I² statistic was used to assess the heterogeneity of the data. Values by subgroups were compared according to the geographical area, age class (≤ 12 months old and > 12 months old), and sample type (bile, faeces, liver, meat/muscle, serum). Sixty-nine publications were selected, with the majority of the studies from Southern Europe (n = 27). The pooled HEV-specific antibody seroprevalence in wild boar was 28% (CI_95% 23-34) and the HEV RNA prevalence 8% (CI_95% 6-10). The analysis highlighted a significant heterogeneity among the estimates from the included studies (I² = 98% and I² = 95% for HEV-specific antibody seroprevalence and viral prevalence respectively). The moderator analysis indicated a statistically significant difference (p-value = 0.03) for the HEV RNA prevalence according to the sample type, with the highest value in bile (17%, CI_95% 9-27), followed by liver (10%, CI_95% 7-14), serum (7%, CI_95% 4-10), faeces (5%, CI_95% 2-9), and meat/muscle (3%, CI_95% 0.04-10). Finally, the HEV RNA prevalence in Europe (8.7, CI_95% 6.7-11) was significantly (p-value = 0.04) higher than in Asia (4, CI_95% 0.6-8). The analysis highlights the important role of wild boar in the epidemiology of HEV.