Influence of age and body condition on astrovirus infection of bats in Singapore: An evolutionary and epidemiological analysis

Mendenhall, Ian H.; Skiles, Maggie M.; Neves, Erica Sena; Borthwick, Sophie A.; Low, Dolyce H.W.; Liang, Benjamin; Lee, Benjamin P.Y.-H.; Su, Yvonne C.F.; Smith, Gavin J.D.

A total of 431 bats from 7 species were trapped and sampled (Table 1) . Astroviruses were only detected in Eonycteris spelaea (30/ 169, 17.8%) and Rhinolophus lepidus (13/36, 36.1%), with an overall detection rate of 9.9% for the pooled oral-rectal swabs (Fig. 1) The astroviruses phylogeny showed that the majority of bat astroviruses (indicated by grey branches) were basal to other mammalian astroviruses, but with a general lack of statistical support (Fig. 3) . The 38 novel bat astroviruses sequences collected in Singapore (denoted by red branches in Fig. 3 ) fell into 2 groups. Two bat astrovirus sequences identified from R. lepidus formed a monophyletic clade (bootstrap [BS] = 100%) that clustered within other Rhinolophus astroviruses from China and Laos (BS < 60%). Similarly, 36 astroviruses sequences from E. spelaea formed a monophyletic lineage (BS = 69%) with two distinct sub-clades, and this lineage was closely related to other pteropodid bat astroviruses from Bangladesh and Laos. Furthermore, the clustering of all E. spelaea astrovirus sequences, despite being collected in different years, suggests sustained transmission in this host. The astroviruses from R. lepidus and E. spelaea from Singapore were genetically dissimilar (nucleotide sequence identity 54.0-57.2%) even though their sampling locations and collection periods were similar.