Characterisation of the whole genome sequence of an avian hepatitis E virus directly from clinical specimens reveals possible recombination events between European and USA strains

Avian hepatitis E virus (aHEV) is the causative agent of an important disease of broiler breeders and layers. aHEV cannot be readily propagated in cell culture and is characterised primarily by sequencing of amplicons generated through several RT-PCRs that target individual genes. This study aims to uncover the origin of current Australian aHEV isolates based on whole genome sequencing using clinical liver tissues. Complete genome sequences of the two aHEV isolates were assembled using Nanopore and Illumina reads. The two isolates possessed only four single nucleotide polymorphisms to each other. Comparison of the sequences with aHEV genome sequences available in the GenBank showed the highest nucleotide sequence identity of 88% with the prototype USA strain (AY535004), 82% with the European (AM943647) and genotype 1 Australian strains (AM943647). Recombination analysis suggested that aHEV isolates characterised in this study are progeny of a cross between a US and a Hungarian strain. Phylogenetic tree and phylogenetic networks constructed using complete genome and individual coding sequences revealed that Australian aHEV isolates formed a distinct clade closer to the USA strains and classified as genotype 2 whereas genotype 1 Australian strain clustered together with South Korean strains.