Natural and experimental hepatitis E virus genotype 3 - infection in European wild boar is transmissible to domestic pigs

Abstract

Hepatitis E virus (HEV) is the causative agent of acute hepatitis E in humans in developing countries, but sporadic and autochthonous cases do also occur in industrialised countries. In Europe, food-borne zoonotic transmission of genotype 3 (gt3) has been associated with domestic pig and wild boar. However, little is known about the course of HEV infection in European wild boar and their role in HEV transmission to domestic pigs. To investigate the transmissibility and pathogenesis of wild boar-derived HEVgt3, we inoculated four wild boar and four miniature pigs intravenously. Using quantitative real-time RT-PCR viral RNA was detected in serum, faeces and in liver, spleen and lymph nodes. The antibody response evolved after fourteen days post inoculation. Histopathological findings included mild to moderate lymphoplasmacytic hepatitis which was more prominent in wild boar than in miniature pigs. By immunohistochemical methods, viral antigens were detected mainly in Kupffer cells and liver sinusoidal endothelial cells, partially associated with hepatic lesions, but also in spleen and lymph nodes. While clinical symptoms were subtle and gross pathology was inconspicuous, increased liver enzyme levels in serum indicated hepatocellular injury. As the faecal-oral route is supposed to be the most likely transmission route, we included four contact animals to prove horizontal transmission. Interestingly, HEVgt3-infection was also detected in wild boar and miniature pigs kept in contact to intravenously inoculated wild boar. Given the high virus loads and long duration of viral shedding, wild boar has to be considered as an important HEV reservoir and transmission host in Europe.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-014-0121-8) contains supplementary material, which is available to authorized users.

Hallmarks of liver lesions in pigs naturally infected by hepatitis E virus genotype 3

“…Lobular activity and portal hepatitis have also been previously experimentally demonstrated in the early stages of infection in chimpanzees inoculated with HEV (Yu et al 2010) and; thus, the data of an acute hepatitis pattern seems to be directly related to HEV-RNA detection in the liver of naturally (Lee et al 2007) and experimentally infected pigs (Halbur et al 2001, Schlosser et al 2014.…”

“…HEV antigens (pORF3) were also observed in Kupffer cells and biliary epithelium in our cases, which is similar to the results of HEV immunostaining in humans (Gupta et al 2012). On the other hand, wild boars and miniature pigs experimentally infected with an isolate of wild boar genotype 3 HEV presented liver immunostaining of pORF2 ranging from mild to marked mainly in Kupffer cells and liver sinusoidal endothelial cells (Schlosser et al 2014).…”

“…Features of hepatic lesions in pigs naturally infected by HEV genotypes 3 and 4 are still little described (Meng et al 1997, Lee et al 2007) although experimental studies in swine using isolates of genotype 3 documented microscopic hepatitis (Halbur et al 2001, Schlosser et al 2014. The aim of this study is to describe the main histopathological liver lesions in naturally HEV genotype 3 infected pigs, which were slaughtered for human consumption in the Eastern Brazilian Amazon, a HEV non-endemic region.…”

Preliminary study on the detection of hepatitis E virus (HEV) antibodies in pigs and wild boars in Poland

“…The time of sampling or the use of a different test could be the reason for the discordant results obtained by us and by Larska et al (9). Several studies have investigated the presence of HEV in wild boars in Italy, Germany, the Netherlands, and France (3,12,17,19). In Europe overall, the seroprevalence varies between 12% in the Netherlands (17) and 61.6% in Slovenia (7), with Spanish seroprevalence at 47.2% (5).…”

“…It should be emphasised that the vast majority of the pig population in Poland have no direct contact with wildlife. Schlosser et al (19) proved that HEV in European wild boars is transmissible to domestic pigs horizontally and these animals have to be considered an important HEV reservoir in Europe (19).…”