Pathogenesis studies with Australian bat lyssavirus in grey‐headed flying foxes (Pteropus poliocephalus)

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Abstract
Objective To examine the susceptibility of the grey‐headed flying fox (Pteropus poliocephalus) to Australian bat lyssavirus (ABL), and to provide preliminary observations on the patho‐genesis of the disease in flying foxes. Procedure Ten flying foxes were inoculated intramuscularly with ABL, and four with a bat‐associated rabies virus. Inoculated animals were observed daily, and clinical samples collected every 9 to 14 days. Animals with abnormal clinical signs were euthanased, and samples collected for histolog‐ical, serological, virological and immunohistological examinations. At 3 months post inoculation (PI), all survivors were euthanased, and each submitted to a similar examination. Results Three ABL‐inoculated flying foxes, and two rabies‐inoculated animals developed abnormal clinical signs between 15 and 24 days PI. All three ABL‐inoculated animals had histological lesions consistent with a lyssavirus infection, and lyssaviral antigen was identified in the central nervous system (CNS) of each. Virus was isolated from the brain of two affected animals. Of the rabies‐inoculated flying foxes, both had histological lesions and viral antigen in the CNS. Virus was recovered from the brain of only one. None of the five affected flying foxes developed anti‐lyssavirus antibodies, but, by 3 months PI, five of the seven ABL‐inoculated survivors, and one of the two rabies virus‐inoculated survivors, had seroconverted. The dynamics of the immune responses were quite variable. Conclusions The response of flying foxes to ABL, administered by a peripheral route of inoculation, was similar to that of bats inoculated peripherally with bat‐derived rabies viruses.