Genetic diversity and phylogenetic analysis of newly discovered bat astroviruses in Korea

Bats have been identified as a natural reservoir for several potentially zoonotic viruses. Recently, astroviruses have been reported in bats in many countries, but not Korea. We collected 363 bat samples from thirteen species at twenty-nine sites in Korea across 2016 and tested them for astrovirus. The detection of the RNA-dependent RNA polymerase (RdRp) gene in bat astroviruses was confirmed in thirty-four bats across four bat species in Korea: twenty-five from Miniopterus fuliginosusi, one from Myotis macrodactylus, four from M. petax, and four from Rhinolophus ferrumequinum. The highest detection rates for astrovirus were found in Sunchang (61.5%, 8/13 bats), and in the samples collected in April (63.2%, 12/19 bats). The amino acid identity of astroviral sequences identified from bat samples was ≥ 46.6%. More specifically, the amino acid identity within multiple clones from individual bats was ≥ 50.8%. Additionally, the phylogenetic topology between astroviruses from different bat families showed a close relationship. Furthermore, phylogenetic analysis of the partial ORF2 sequence of bat astroviruses was found to have a maximum similarity of 73.3–74.8% with available bat astrovirus sequences. These results indicate potential multiple-infection by several bat astrovirus species in individual bats, or hyperpolymorphism in the astrovirus strains, as well as the transmission of astroviruses across bat families; furthermore, our phylogenetic analysis of the partial ORF2 implied that a novel astrovirus may exist. However, the wide diversity of astroviral sequences appeared to have no significant correlation with bat species or the spatiotemporal distribution of Korean bat astroviruses.