Objectives: Wobbly possum disease (WPD), a neurological disease of the Australian brushtail possum (Trichosurus vulpecula), was first described in 1995 in a group of captive possums at a New Zealand research facility [1]. It was subsequently observed in free-living possums, and reproduced under experimental conditions [2, 3]. The early stages of WPD are characterised by behavioural changes (loss of appetite, decreased interest in the environment, temperament changes), followed by progressive ataxia. Histologically, the disease is characterised by inflammation of the brain and of several other tissues. Recently, we have identified a novel virus in archival tissues from WPD-affected possums [4]. The objective of the current study was to confirm the aetiological involvement of this virus in WPD.
Methods: The virus was grown in primary liver macrophages and purified using density gradient ultracentrifugation [5]. Possums caught from the wild were individually housed. Following acclimatization period of up to 4 weeks, each possum in group 1 (n=4) received ~1 x 107 TCID50 of a purified cell culture isolate, each possum in group 2 (n=4) received ~1 x 106 TCID50 of a cell lysate from inoculated cultures, and each possum in group 3 (n=4) received 1 mL of a standard inoculum prepared from tissues of WPD-affected possums. Control possums (n=4) received either a gradient material prepared from uninoculated cultures (n=2) or nothing (n=2). All inoculations were performed via intraperitoneal injection.
Results: All but one possums in groups 1-3 developed clinical signs of WPD approximately 2 weeks post inoculations and were euthanized. One possum died prior to the development of neurological signs, and 3/5 joeys died. Control possums did not demonstrate any clinical signs of WPD. High levels of viral RNA were detected in tissues from all possums that received infectious inocula, but not from control possums.
Acknowledgements: This work was supported by the Massey University Research Fund.