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

This research investigates the pathological effects of Borna disease in horses, highlighting the neurological signs, disease progression, and virological evidence in the brain and nervous system. The study finds that horses infected with Borna disease exhibit reduced mental function and issues with gait, and this is likely linked to the presence of the virus in the thalamus and hippocampus of the horse’s brain.

Clinical Findings

• The study observed consistent clinical symptoms in afflicted horses, including decreased mental function and movement issues. Symptoms also escalated to anorexia and loss of proprioception (awareness of the position of one’s body), showing the progressive nature of the disease.
• Cranial nerve failure was demonstrated by paralysis of the animal’s pharynx, excessive salivation, teeth grinding and blindness.

Virology and Immunopathology

• Upon examination, infectious Borna virus was present in all the animal brains studied but did not appear uniformly in all brain areas. Specifically, the virus was consistently found in the thalamus and the hippocampal area, suggesting these areas may be particularly susceptible.
• Methods used to detect virus presence included Reverse Transcriptase-Polymerase Chain Reaction assay and immunohistochemistry, which detect virus-specific RNA and antigen respectively.
• Other compartments of the central nervous system did not regularly yield the virus, and no infection was found in the peripheral nervous system or peripheral organs.
• The scientists also observed lymphocytic inflammatory reactions and increased expressions of MHC class I and II antigens in the brain, indicating an immune response to the Borna disease virus.

Infection Route

• Given the abundance of Borna disease virus proteins and nucleic acids in the trigeminal system compared to the olfactory system, the researchers propose that infection may occur through the trigeminal nerve.
• The trigeminal nerve is one of the key nerves in the horse’s head and if affected, it can lead to many of the observed symptoms.