Cross-Species Infection and Characterization of Avian Hepatitis E Virus

As novel or variant strains of HEV continue to evolve rapidly both in humans and other animals, it is important to develop a rapid pre-sequencing screening method to select field isolates for further molecular characterization. Two heteroduplex mobility assays (HMA) were developed to genetically differentiate field strains of swine HEV and avian HEV from known reference strains. It was shown that the HMA profiles generally correlate well with nucleotide sequence identities and with phylogenetic clustering between field strains and the reference swine HEV or avian HEV strains. Therefore, by using different HEV isolates as references, the HMA developed in this study can be used as a pre-sequencing screening tool to identify variant HEV isolates for further molecular epidemiological studies. Our previous study showed that avian HEV antibody is prevalent in apparently healthy chickens. A prospective study was conducted on a known seropositive but healthy chicken farm. Avian HEV was identified from the healthy chicken flock. Avian HEV isolates recovered from the healthy chicken share 70-97% nucleotide sequence identities with those isolates which cause hepatitis-splenomegaly (HS) syndrome based on partial helicase and capsid gene regions. Recovery of identical viruses from the experimentally inoculated chickens in the subsequent transmission study further confirmed our field results. The capsid gene of avian HEV isolates from chickens with HS syndrome were also characterized and found to be heterogeneic, with 76-100% nucleotide sequence identities to each other. The study indicates that avian HEV is enzootic in chicken flocks and spread subclinically among chicken populations, and that the virus is heterogeneic.