Abstract
Silver-haired bats, (Lasionycteris noctivagans) are semi-colonial, migratory tree bats that have infrequent contact with humans. Despite the species rarity, the L. noctivagans rabies variant is the most commonly reported rabies virus variant (RABV) in domestically acquired human rabies cases in the US. Unlike big brown bats (Eptesicus fuscus) and little brown bats (Myotis lucifugus), L. noctivagans are not considered true hibernators. It is unknown if RABV can overwinter in hibernating L. noctivagans or is only maintained in members of this taxa that migrate to warmer climates. To better understand RABV overwintering in this species, L. noctivagans were inoculated intramuscularly with either a homologous RABV (L. noctivagans Virus 1) or one of two heterologous RABV (Eptesicus fuscus Virus 2 and Myotis lucifugus Virus 1). Five days following inoculation, L. noctivagans were placed in a hibernation chamber for 6 weeks. Our results demonstrate that rabies virus can overwinter in L. noctivagans yet the incubation period was extended 6 weeks when compared to bats maintained at ambient temperatures. Additionally, we found that the longer the incubation period, the greater the viral dissemination to the salivary glands. Similar to our previous studies, L. noctivagans were most susceptible to a homologous variant. In summary, we found that RABV incubation is extended following a subcutaneous exposure or maintenance in hibernation and longer incubation times increase dissemination and potential for transmission.
Highlights
Rabies virus (RABV) can be found in wild animals year round, yet infections increase substantially during certain times of the year
Previous studies have suggested that the L. noctivagans RABV may be more virulent, yet it is unknown if L. noctivagans bats have an altered susceptibility to homologous RABV thereby increasing the number of rabid L. noctivagans in the wild populations as compared to E. fuscus and M. lucifugus [15,16,17,18,19]
If the answer was dependent on percentage of rabies positive L. noctivagans submitted to the NYSDOH rabies laboratory, the data would imply that tree bats, including L. noctivagans, had an increased susceptibility to rabies when compared to the commensal species E. fuscus and M. lucifugus
Summary
Rabies virus (RABV) can be found in wild animals year round, yet infections increase substantially during certain times of the year. In the Northeastern US, the percentage of rabies positive animals increases from June through October [1]. The increase coincides with warmer weather, bats moving to summer roosts and nursery colonies, and increased activity of wildlife. Warmer weather results in more human outdoor activity and greater likelihood for interaction between the general public and wildlife.
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