[Immunopathology of Borna disease in the horse: clinical, virological and neuropathologic findings].

Abstract

Tissues from nine horses and one donkey suffering from natural Borna disease were investigated. Clinically, all animals demonstrated progressive reduced mentation and aggravating gait disturbances. During the clinical course anorexia and progressive loss of proprioception were observed. Cranial nerve failure was accompanied by signs of pharyngeal paralysis, sialorrhea, bruxism, and by blindness. Virologically, infectious virus was detected in the brain of all animals investigated but was not found regularly in all areas of the brain. However, in all cases, infectivity was found in the thalamus and the hippocampal area. In contrast, in other compartments of the central nervous system virus was not detected regularly. These findings correlate well to the results obtained from assaying Borna virus-specific RNA by Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and virus specific antigen by immunohistochemistry. No evidence of infection was found in the autonomic nervous system and peripheral organs. Immunomorphologically, lymphocytic inflammatory reactions and increased expressions of MHC class I and class II antigen were found in the brain as well as in the trigeminal and olfactory system. No evidence of inflammation was found in the retina. From the finding that BDV-proteins and nucleic acids were even more abundant in the trigeminal system as compared to the olfactory system, we conclude that infection may have occurred via the trigeminal nerve.