First cases of European bat lyssavirus type 1 in Iberian serotine bats: Implications for the molecular epidemiology of bat rabies in Europe

Previous studies have shown that EBLV-1 strains exclusively hosted by Eptesicus isabellinus bats in the Iberian Peninsula cluster in a specific monophyletic group that is related to the EBLV-1b lineage found in the rest of Europe. More recently, enhanced passive surveillance has allowed the detection of the first EBLV-1 strains associated to Eptesicus serotinus south of the Pyrenees. The aim of this study is the reconstruction of the EBLV-1 phylogeny and phylodynamics in the Iberian Peninsula in the context of the European continent. We have sequenced 23 EBLV-1 strains detected on nine E. serotinus and 14 E. isabellinus. Phylogenetic analyses were performed on the first 400-bp-5’ fragment of the Nucleoprotein (N) gene together with other 162 sequences from Europe. Besides, fragments of the variable region of the phosphoprotein (P) gene and the glycoprotein-polymerase (G-L) intergenic region were studied on Spanish samples. Phylogenies show that two of the new EBLV-1a strains from Iberian E. serotinus clustered together with French strains from the North of the Pyrenees, suggesting a recent expansion southwards of this subtype. The remaining seven Iberian strains from E. serotinus grouped, instead, within the cluster linked, so far, to E. isabellinus, indicating that spatial distribution prevails over species specificity in explaining rabies distribution and supporting interspecific transmission. The structure found within the Iberian Peninsula for EBLV-1b is in concordance with that described previously for E. isabellinus. Finally, we have found that the current EBLV-1 European strains could have emerged only 175 years ago according to our evolutionary dynamics analyses.
Author summary Rabies is caused by at least fourteen different viruses of the genus Lyssavirus. Although the classical rabies virus transmitted by the dog accounts for most human cases, most lyssaviruses are hosted by bats, which are able to transmit the disease to humans. The European bat lyssaviruses 1 (EBLV-1) and 2 (EBLV-2) have caused human rabies in Europe, while more than 90% of the bat rabies cases have been reported from serotine bats (Eptesicus serotinus) infected by EBLV-1. These cases clearly accumulate in certain areas of Europe, but the factors driving this distribution are unknown. The evolutionary relationships among these viral strains provide valuable information, however, they are only partially known. The south of the Iberian Peninsula is the only location within Europe with an additional reservoir for EBLV-1, the isabelline serotine bat (Eptesicus isabellinus) which is present also in North Africa. In this study we have reconstructed the EBLV-1 phylogeny and phylodynamics in the Iberian Peninsula in the context of the European continent. Our results suggest that some lineages have longer evolutionary history in their distribution areas, than others which seem to be in the process of a geographical expansion.