Circulation of rabies-related lyssaviruses
Serological analyses performed in 2016 showed neutralization of EBLV-1b in 119 out of 270 (44%) individual blood samples from South TyroleanM. myotis, with serological titers ranging from 2 to 2.4 LogD50/ml (Table 4). In addition, 46 samples (17%) from different roosts and seasons showed viral inhibition below the determined cutoff for the method. Observed sero-prevalence and specific antibody titers increased after the birth pulse, occurring at the end of May across the whole population (Table 4). Despite the percentage of seropositive individuals varied from 0 to 26.5% among colonies in early May, the seasonal increasing trend was confirmed in all colonies (Table 4, Figure 4). Overall, animals under 1 year of age showed a higher percentage of positivity and higher titers compared to adults; however, this result might be confounded by the fact that we found only few adult animals in September, when sero-prevalence has been proven considerably higher in all colonies (Table 4, Figure S1). Indeed, taking into account the correlation among bats within the same colony, results from multivariable analyses suggest that the influence of seasonality alone might explain the qualitative (QIC=173.1630, AUC=90.57) and quantitative (AIC=-104.9) serological pattern found in the dataset (Supplementary methods). Overall, these analyses confirmed the higher probability to find sero-positive bats in autumn as compared to spring (94.17% vs 9.55%), also showing a mean significantly higher serological titer (2.32 vs 2.11 LogD50/ml) (Table 5, Figure 5) and regardless of the age category. Indeed, we found no significant difference in serological titers between youngsters and adults in September (Figure 5).