Morphometric analysis of the retina from horses infected with the Borna disease virus.
Authors: Dietzel J, Kuhrt H, Stahl T, Kacza J, Seeger J, Weber M, Uhlig A, Reichenbach A, Grosche A, Pannicke T
Journal: Veterinary pathology
Summary
# Editorial Summary: Retinal Pathology in Equine Borna Disease Blindness is a hallmark clinical sign of Borna disease in horses, yet the underlying retinal mechanisms have remained unclear until now. Dietzel and colleagues conducted a quantitative morphological analysis of retinal tissue from nine naturally infected horses (confirmed by detection of Joest-Degen inclusion bodies at post-mortem), comparing neuron and Müller glial cell counts against unaffected controls using histological and immunohistochemical staining of paraffin sections. The diseased horses demonstrated a significantly reduced neuron-to-Müller cell ratio across the whole retina (8.5 ± 0.4 versus 17.6 ± 0.8 in controls; P < 0.01), indicating substantial photoreceptor loss, though the severity of retinal changes varied between individuals. Beyond explaining the visual dysfunction observed clinically in affected animals, these findings establish that Borna disease targets neuronal populations within the retina itself, adding an important layer to our understanding of disease pathogenesis. For practitioners managing horses with suspected neurological disease, this work reinforces the likelihood of permanent visual impairment in Borna-infected animals and supports the need for careful ophthalmological assessment alongside neurological evaluation.
Read the full abstract on PubMed
Practical Takeaways
- •Blindness in horses with suspected Borna disease is associated with measurable photoreceptor degeneration, confirming a neurological basis for this clinical sign
- •Retinal changes in Borna disease vary between affected horses, suggesting variable progression or severity of neuronal damage
- •This pathologic information supports the neuroinflammatory nature of Borna disease and its multi-system neurological effects in equine patients
Key Findings
- •Borna disease causes significant retinal degeneration in horses with neuron-to-Müller cell ratio reduced from 17.6±0.8 in controls to 8.5±0.4 in diseased horses (P<0.01)
- •Histologic changes in affected retinae were variable in degree across the 9 diseased horses examined
- •Loss of photoreceptors and other retinal neurons likely explains blindness observed in Borna disease-infected horses