Swine hepatitis E virus: cross-species infection and risk in xenotransplantation

Swine hepatitis E Virus (swine HEV), a ubiquitous agent recently discovered in pigs, is antigenically and genetically closely related to the human HEV. Swine HEV infection in pigs generally occurs at about 2-3 months of age, and about 80%-100% of the pigs in commercial farms in the USA were infected. Swine HEV infections have now been recognized in pigs in many other countries of the world. Interspecies transmission has been documented, as swine HEV infects non-human primates and some strains of human HEV infect pigs. Recent seroepidemiological studies showed that swine veterinarians and other pig handlers are at higher risk of HEV infection compared to normal blood donors. In addition, novel strains of human HEV recovered from hepatitis patients in the USA, Japan and Taiwan are genetically more closely related to strains of swine HEV from respective countries than to other strains of human HEV. The ubiquitous nature of the virus in pigs and the demonstrated ability of cross-species infection raise a potential concern for swine HEV infection in xenotransplantation with pig organs. This chapter discusses the recent advances in HEV research with emphases on potential zoonosis and xenozoonosis.