Bat rabies--a Gordian knot?

Although classical rabies is one of the earliest identified and best studied infectious diseases, there is still limited knowledge about lyssaviruses and their major natural hosts, bats. Focussing on bat rabies in Europe caused by European bat lyssaviruses 1 (EBLV-1) and 2, for instance the association of EBLV-1 to Eptesicus bats and EBLV-2 to Myotis daubentonii and M. dasycneme together with an apparent clustering of cases is one question still to be answered. Furthermore, the question whether EBLVs are less virulent or bats less susceptible is the key to the understanding of the disease. Accumulating evidence from experimental studies and field observations, however, has resulted in contradicting hypotheses. Serological surveys, using tools developed for classical rabies, are often used for bat rabies surveillance. However, such surveys are hampered by the lack of validated methods applicable for bat sera. Bats seem to play a prominent role as reservoir for viral pathogens and the unique biology of bats especially the immune response may contribute to this. Considering all known aspects, bat rabies seems to form a yet unsolvable entanglement, reminiscent of the ancient tale of the Gordian knot. In this manuscript we will not be able to untangle this knot, but we hope to offer some suggestions of where to start.