Lyssavirus distribution in naturally infected bats from Germany

In Germany, to date three different lyssavirus species are responsible for bat rabies in indigenous bats: the European Bat Lyssaviruses type 1 and 2 (EBLV-1, EBLV-2) and the Bokeloh Bat Lyssavirus (BBLV) for which Eptesicus serotinus, Myotis daubentonii and Myotis nattereri, respectively, are primary hosts. Lyssavirus maintenance, evolution, and epidemiology are still insufficiently explored. Moreover, the small number of bats infected, the nocturnal habits of bats and the limited experimental data still hamper attempts to understand the distribution, prevalence, and in particular transmission of the virus. In an experimental study in E. serotinus a heterogeneous dissemination of EBLV-1 in tissues was detected. However, it is not clear whether the EBLV-1 distribution is similar in naturally infected animals. In an attempt to further analyze virus dissemination and viral loads within naturally infected hosts we investigated tissues of 57 EBLV-1 positive individuals of E. serotinus from Germany by RT-qPCR and compared the results with those obtained experimentally. Additionally, tissue samples were investigated with immunohistochemistry to detect lyssavirus antigen in defined structures. While in individual animals virus RNA was present only in the brain, in the majority of E. serotinus viral RNA was found in various tissues with highest relative viral loads detected in the brain. Interestingly, viral antigen was confirmed in various tissues in the tongue including deep intralingual glands, nerves, muscle cells and lingual papillae. So, the tongue appears to be a prominent site for virus replication and possibly shedding.