# Rabies, host population structure, and cross-species transmission to the migratory bat Tadarida brasiliensis in Chile

## TL;DR

This study explores how the migration of Brazilian free-tailed bats in Chile affects rabies virus spread and cross-species transmission.

## Contribution

The study reveals asymmetric cross-species rabies virus transmission patterns in migratory Brazilian free-tailed bats in Chile.

## Key findings

- Migratory behavior homogenizes population and rabies virus structure of Tadarida brasiliensis across Chile.
- T. brasiliensis is infected by rabies viruses from other bat species, but does not transmit its virus back.
- Urban areas may act as hotspots for cross-species rabies virus transmission.

## Abstract

Although many bat species migrate, the consequences of migration for bat population structure and rabies virus transmission remain poorly understood. Understanding the spatiotemporal dynamics of bat rabies (Lyssavirus rabies) transmission is important to prevent rabies spillovers to dead-end hosts, including humans. Here, focusing on the long-distance migratory Brazilian free-tailed bat (Tadarida brasiliensis) in South America, we identify the extent of host population and rabies virus structure across Chile. The analysis of 112 cytochrome b sequences from T. brasiliensis individuals and 144 rabies virus sequences submitted to the Chilean national rabies surveillance showed a lack of geographic clustering by municipality or region in Chile. This lack of clustering suggests that the migratory behavior of this species might be homogenizing the population structure of T. brasiliensis and its species-specific rabies virus (TbRV-SA). While most rabies virus sequences of T. brasiliensis (92%) corresponded to the TbRV-SA lineage, we also detected T. brasiliensis individuals infected by rabies viruses that are more strongly associated with other bats, including Lasiurus spp., Histiotus spp., and Myotis spp (8%). In contrast, no other bat species were infected by TbRV-SA, suggesting the potential for a predominant asymmetric cross-species transmission observed in Chile. These results suggest that rabies risk could vary according to migratory bat movement patterns and community composition, especially in areas where cross-species transmission may be facilitated. Our study highlights the need to anticipate the spillover risk to humans and domestic animals associated with the long-distance spread of rabies virus in T. brasiliensis, and calls attention to clarify the role of urban areas as potential hotspots for cross-species transmission.

In this study, we explored how the long-distance movement of the Brazilian free-tailed bats can influence the spread of its rabies virus in Chile. This bat is known for traveling hundreds of kilometers, and we aimed to understand whether these movements influence the genetic distribution of this bat and of its rabies virus. We analyzed genetic data from both bats and the rabies virus they carried. Our results showed that the genetic structure of bats and their specific rabies virus were mixed across different Chilean regions, likely related to their migratory behavior. We also found that the Brazilian free-tailed bat was infected by the virus of the other three bat species, but it appeared not to transmit rabies to other insectivorous bats in our study area. Recognizing these patterns can help to understand and anticipate the spread of rabies virus and other pathogens in bats to humans and domestic animals.