Disease Surveillance and Monitoring in Wild-Ranging Carnivores in Taiwan: The First Identification and Characterization of Rabies Virus in Ferret Badgers
Date Issued
2015
Date
2015
Author(s)
Chiou, Hue-Ying
Abstract
The objective of this study was to investigate the causes of death and potential diseases carried by the wild-ranging carnivores in Taiwan. For those interesting and essential diseases, further studies in depths were performed. A total of 51 carcasses from rescued but dead or road-killed carnivores, collected during the period of August 2011 to January 2015, were necropsied for histopathology, molecular and immunological assays, microbiology, and parasitology. The cases included 31 Taiwan ferret badgers (TWFBs) (Melogale moschata subaurantiaca), 12 masked palm civets (MPCs) (Paguma larvate taivana), 5 small Chinese civets (SCCs) (Viverricula indica pallida), and 3 crab-eating mongooses (CEMs) (Herpestes urva). Zoonotic rabies and fatal canine distemper were diagnosed in 4 TWFBs and 3 MPCs, respectively. The characteristic pathological changes of rabid TWFBs were nonsuppurative meningoencephalomyelitis, ganglionitis, and formation of typical intracytoplasmic Negri bodies with brain stem affected the most. Additionally, variable spongiform degeneration, primarily in the perikaryon of neurons and neuropil, was observed in the cerebral cortex, thalamus, and brain stem. In the non-nervous tissue, representative lesions included adrenal necrosis and lymphocytic interstitial sialoadenitis. By immunohistochemical (IHC) staining as well as fluorescent antibody test (FAT), positive viral antigens were detected in the perikaryon of the neurons and axonal and/or dendritic processes in the nervous tissue and in the macrophages scattered in various tissues throughout the body. The findings suggest that brain stem, cerebral cortex, hippocampus, thalamus and hypothalamus are ideal sampling regions for molecular diagnosis of RABV in TWFBs. Retrospective study using archived formalin-fixed and paraffin-embedded tissues of TWFBs revealed the earliest IHC-positive rabid TWFB case in 2004. To examine the origin of this viral strain, we sequenced three complete genomes and acquired multiple rabies virus (RABV) nucleoprotein (N) and glycoprotein (G) sequences. Phylogeographic analyses demonstrated that the RABV of TWFB (RABV-TWFB) is a distinct lineage within the Asian group, and has been differentiated from its closest lineages, China I (including Chinese ferret badger isolates; RABV-CNFB) and Philippines, 158-210 years before present. The most recent common ancestor of RABV-TWFB was originated 91-113 years ago. The ancient origin of the endemic RABV-TWFB illustrates that this RABV variant could be cryptically circulated in the environment without being recognized for a long period of time. The underlying mechanism is worthy of further study and may shed light on the complex interaction between RABV and its host.
Subjects
Rabies
Taiwan ferret badger
Carnivores
Phylogeographic analyses
Type
thesis
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