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

Abstract

Bats are unique mammals that are reservoirs of high levels of virus diversity. Although several of these viruses are zoonotic, the majority are not. Astroviruses, transmitted fecal-orally, are commonly detected in a wide diversity of bat species, are prevalent at high rates and are not thought to directly infect humans. These features make astroviruses useful in examining virus evolutionary history, epidemiology in the host, and temporal shedding trends. Our study screened for the presence of astroviruses in bats in Singapore, reconstructed the phylogenetic relations of the polymerase genes and tested for population characteristics associated with infection. Of the seven species screened, astroviruses were detected in Rhinolophus lepidus and Eonycteris spelaea. The R. lepidus sequences grouped with other Rhinolophus astrovirus sequences from China and Laos, while the Eoncyteris sequences formed a distinct clade with astroviruses from Rousettus spp. in Laos and Pteropus giganteus in Bangladesh, but not with other E. spelaea sequences. Longitudinal collections of Eonycteris feces demonstrated variable shedding. Juvenile status of bats was a risk factor for astroviruses. This study highlights the diversity of astroviruses in nectivorous and insectivorous bats in Singapore and provides a predictive framework for understanding astrovirus infection in these bats. It also suggests that in addition to host phylogenetic relatedness, host ecology, such as roosting behavior, may drive co-infections, virus maintenance and spillover.

Keywords: Bat borne virus; Eonycteris spelaea; Epidemiology; Phylogenetics; Pooling prevalence; Rhinolophus lepidus; Southeast Asia.

Fig. 1

Photographs of Rhinolophus lepidus (Blyth's horseshoe bat) and Eonycteris spelaea (Cave nectar bat).

Fig. 2

Temporal variation in the infection rate of astrovirus detected in the feces collected from an Eonycteris spelaea colony using a hemi-nested PCR detecting the RNA-dependent reverse polymerase gene.

Fig. 3

Maximum likelihood phylogeny of the RNA-dependent RNA polymerase (RdRp) region of global astrovirues. Red branches denote novel bat astrovirus generated from this study, whereas the grey branches represent bat astrovirus collected from other geographical regions. The coloured branches denote different host species. Bootstrap values > 50% are indicated at major nodes. The scale bar represents the nucleotide substitutions per site. The insert on the right shows the details of astrovirus strains in Clade 1 and 2. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Supplementary Fig. 1

Maximum likelihood phylogeny of the RNA-dependent RNA polymerase (RdRp) region of global astrovirues. Red branches denote novel bat astrovirus generated from this study, whereas the gray branches represent bat astrovirus collected from other geographical regions. The coloured branches denote different host species. Bootstrap values greater than 50% are indicated at major nodes. The scale bar represents the nucleotide substitutions per site. The insert on the right shows the details of astrovirus strains in Clade 1 and 2.