Histopathology and immunohistochemistry of bats infected by Australian batlyssavirus

Objective To describe the lesions and distribution of viral antigens in bat s infected by Australian bat lyssavirus. Design A retrospective histopathological and immunohistochemical study of b ats naturally infected with the virus. Procedure Tissues from 37 infected bats were examined. Nineteen flying foxe s (fruit bats) and two insectivorous bats were examined in detail. Brains o f another 16 flying foxes were poorly fixed and were examined less fully. Result Lesions varied considerably between individuals and, where present, were mostly those of nonsuppurative meningoencephalomyelitis and ganglioneu ritis similar to lesions seen in rabies and rabies-like diseases. The numbe r of cells with intracytoplasmic inclusion bodies (Negri bodies) was variab le; none were seen in some bats. Intracytoplasmic vacuolation of neurons wa s a common finding. Lesions occurred throughout the central nervous system but were most frequent and severe in the hippocampus, thalamus and midbrain , and medulla oblongata and pens. Indirect immunoperoxidase tests far lyssa virus antigen reactions varied in intensity and distribution, but also occu rred mostly in the hippocampus, thalamus and midbrain, and medulla oblongat a and pens. In peripheral tissues, reactions were seen in autonomic ganglia , in nerve plexuses of the gastrointestinal tract, in nervous tissues withi n muscles and immediately adjacent to individual muscle fibres, in an adren al medulla, and in epithelial tissues in one of eight salivary glands exami ned. Conclusion The main lesion in Australian bat lyssavirus infection is nonsup purative inflammation similar to that seen in rabies and other rabies-like diseases, except that the number of Negri bodies is more variable. Reaction s to immunoperoxidase tests for lyssavirus vary in intensity and distributi on and may occur in both central and peripheral nervous systems. These reac tions do not always occur in the salivary glands, even if brain infection i s present.