Unraveling the role of Myotis myotis in the ecology and transmission of rabies-related lyssaviruses (RRLVs)

Abstract

Purpose: Insectivorous bats have been found to carry a variety of Rabies-Related Lyssaviruses (RRLVs) across Europe, among which European bat Lyssavirus 1 (EBLV-1) is the most widely distributed. Despite the majority of lethal infections are reported from serotine bats, serological data suggest that other species might have a role in the ecology of this pathogen. EBLV-1 has been associated with spillover events to humans, domestic and wildlife animals, causing a neurological disease clinically indistinguishable from classical rabies. Unraveling its ecology would then be crucial in predicting and mitigating associated risks for public health. Methods & Materials: During 2012-2018, we investigated the role of Myotis myotis in the maintenance and transmission of EBLV-1, through the longitudinal screening of roosts for neutralizing antibodies and viral shedding. Five neighboring maternal colonies were investigated in Northern Italy, whose connectivity was assessed using genetic and capture-recapture studies. Results: Antibodies neutralizing EBLV-1 were detected yearly, confirming that M. myotis are constantly exposed to the virus in the area and do survive the infection. In addition, longitudinal data revealed wide oscillations of antibodies during a single reproductive season, suggesting waning of antibodies and waves of infection. All colonies showed similar serological trends over consecutive years. Indeed, we found evidence for genetic panmixia at the nuclear and mitochondrial level and confirmed the movement of adult females between roosts. Conclusion: Altogether, our results support the role of M. myotis as natural host for an EBLV1-like RRLV. While this bat species usually inhabits underground sites in the Mediterranean areas, M. myotis is a strictly house dweller species in northern areas, with all colonies investigated in this study being located in church roofs. Based on both serological and virological findings, we suggest that the risk for human exposure to the virus is limited, with viral excretion restricted to short predictable windows of time. We predict that this study will be useful to secure public health while maintaining a positive relationship between humans and these large vesper bats, whose critical role in the control of pest insects is well recognized in the area.