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.

The most predictive model for astrovirus infection included bat age and bat species: log(p/1 − p) = β o + β 1 (Bat Age) + β 2 (Bat Species). In the crude analysis, bat age was found to be a significant risk factor for astrovirus, (OR: 0.44, P: 0.02, 95% CI: 0.22-0.90) providing evidence that astroviruses were less likely to be detected in adults. Thus we estimate the odds of astrovirus infection to be reduced by 56% given an adult bat. Similarly, unadjusted bat species was a strong indicator of astrovirus, (OR: 2.62, P: 0.02, 95% CI: 1.19-5.75); thus, it is estimated that the odds of contracting astrovirus infection are~2.6× greater among Rhinolophus lepidus bats as compared to the referent group Eonycteris spelaea bat. The five remaining species were automatically eliminated from the model, as none of them predicted astrovirus (astrovirus detection rate = 0%). However, adjusting for bat age in the larger model displayed more modest evidence for a bat age effect (OR: 0.59, P: 0.20, 95% CI: 0.26-1.34). Although, bat species did not appear to be an important confounder in the bat age/astrovirus relationship (determined by the adjusted bat age odds ratio lying between the 95% CI in the unadjusted model). Hence, the evidence in these data suggest, but are insufficient to conclude, that bat age has an independent effect on astrovirus outcome beyond that of bat species (Table 3) .