5. Conclusions

This lead to the public health recommendation that individuals that are in close contact with bats should be vaccinated, in addition to simple measures such as wearing gloves whilst handling bats. Furthermore, post-exposure vaccination could be offered to those that were bitten or had inadvertently been in contact with bats. This could also be extended to domestic

All evidence to date suggests that the Daubenton's bat is the wildlife reservoir for EBLV-2. However, many questions remain concerning the persistence of EBLV-2 within the Daubenton's bat population in Europe. The virus is only detected sporadically. In the UK, this equates to a single isolation a year but this meagre number is presumably the tip of the iceberg of what must be constant virus transmission events occurring whilst the bats are active. With the exception of two bats submitted in May, the majority of submissions in the UK occur in late summer and early autumn (Figure 2). The incubation period, the time from exposure to the development of disease or death, for lyssaviruses in bats is highly variable. By their nature, this cannot be established in wildlife populations as the timing of the transmission event is not known. In a unique case, EBLV-2 was detected in a bat that had been held in captivity for 9 months [42]. Captive studies in Daubenton's bats reported an incubation period of 33 days [35] after infection by the sub-dermal route. The later study involving EBLV-1 infection of serotine bats gave incubation periods between 17 and 26 days following sub-dermal or intramuscular infection [36]. This suggests that the incubation period varies from just over 2 weeks to over 9 months, with factors such as virus dose and route of exposure influencing the time to development of disease. The presence of virus in the salivary glands and taste buds of infected bats implicates biting as the main means of transmission. This could presumably occur at a number of points in the Daubenton's bat life cycle including swarming and mating just prior to hibernation, to the formation of colonies during the summer months. The composition of UK

Figure 2. Seasonal distribution of EBLV-2 infected Daubenton's bats submitted for rabies testing in the UK (1996–2017).

animals, particularly cats that catch bats.

4. Discussion

106 Bats

When the second case of EBLV-2 infection occurred in a human in 2002, very little was known about the biology of the virus and its relationship with its bat reservoir leading some authors to describe the relationship as an ecological enigma [48]. Since then advances have been made in the detection of more lyssavirus species in bat populations, the virus distribution in the bat host, the derivation of the complete EBLV-2 genome and the establishment of clear public health measures aimed at protecting those that handle bats. This includes the wearing of gloves to prevent exposure to virus and the knowledge that current vaccines against rabies will prevent infection with EBLV-2. However, much is not known, in part due to the difficulties in studying a protected, nocturnal, flying mammal. Lyssaviruses form intimate relationships with particular bat species that maintain the virus in the environment [49]. This could imply adaptation to the host that favours continued transmission in that host but limiting the viruses' ability to infect another species. Alternatively, host behaviour such as roosting, dispersal and mating could be drivers for conspecific transmission. Indeed, both may function to restrict particular viruses to a single bat species. It is clear that further multidisciplinary research will be needed to answer fundamental questions on the maintenance of EBLV-2 in the Daubenton's bat.

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