Large circulation of a novel vesiculovirus in bats in the Mediterranean region

Bats are the natural reservoirs of a variety of emerging or re-emerging viruses. Among them, rabies virus (genus Lyssavirus , family Rhabdoviridae ) is of the first and most iconic described in these animals. Since its first description, various new bat lyssaviruses have been regularly described. Apart from lyssaviruses, other bat rhabdoviruses have been also identified, including members of the Vesiculovirus , Ledantevirus and more recently Alphanemrhavirus and Tupavirus genera. However, the family Rhabdoviridae is one of the most abundant and diverse viral families, with 318 officially recognized species divided into 3 subfamilies and 46 different genera. Thus, the number of bat- associated rhabdoviruses is probably higher.

In this study, we first developed and validated a combined nested RT-qPCR technique (pan-rhabdo RT-nqPCR) dedicated to the broad detection of animal rhabdovirus. After validation, this technique was used for a large retrospective screening of archival bat samples ( n = 1962), including blood ( n = 816), brain ( n = 723) and saliva ( n = 423). These samples were collected from various bat species over a period of 12 years (2007-2019) in 9 different countries in Europe and Africa. A total of 23 samples (1.2%) from Miniopterus schreibersii , Rhinolophus euryale and Rhinolophus ferrumequinum bat species was found positive for rhabdovirus infection, including 17 (2.1%) blood and 6 (1.4%) saliva samples, all collected from bats originated from the Mediterranean region.

The complete virus genome sequences were obtained by next-generation sequencing for most of the positive samples. Molecular and phylogenetic analysis of these sequences demonstrated that these virus isolates, named Mediterranean bat virus (MBV), were closely related, and represented a new species Vesiculovirus mediterranean within the Vesiculovirus genus. MBV was more specifically related to the other bat vesiculoviruses previously described in China and North America, together clustering into a distinct group of bat viruses within this genus. Interestingly, our results suggest that MBV is widely distributed, at least in the West part of the Mediterranean region, where it can act as an arbovirus infecting and circulating in multiple bat species. These findings expand the host range and the viral diversity of bat vesiculoviruses and pave the way for further investigations to determine the route of transmission and the dynamic of diffusion of these viruses into bat colonies, as well as to evaluate their potential hazard for public health.