Sample collection for this project was performed on the farm from which the horses originated (confidential), and all diagnostic tests were performed at the University of California, Davis Veterinary Medical Teaching Hospital.
Equine Degenerative Myeloencephalopathy in Lusitano Horses
Article first published online: 16 NOV 2011
Copyright © 2011 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 25, Issue 6, pages 1439–1446, November-December 2011
How to Cite
Finno, C.J., Higgins, R.J., Aleman, M., Ofri, R., Hollingsworth, S.R., Bannasch, D.L., Reilly, C.M. and Madigan, J.E. (2011), Equine Degenerative Myeloencephalopathy in Lusitano Horses. Journal of Veterinary Internal Medicine, 25: 1439–1446. doi: 10.1111/j.1939-1676.2011.00817.x
- Issue published online: 16 NOV 2011
- Article first published online: 16 NOV 2011
- Manuscript Accepted: 30 AUG 2011
- Manuscript Revised: 22 AUG 2011
- Manuscript Received: 7 MAY 2011
- State of California pari-mutuel fund
- Center for Equine Health
- Neuro axonal dystrophy;
- Vitamin E
Equine degenerative myeloencephalopathy (EDM) is a neurodegenerative disorder that has been previously associated with low vitamin E concentrations.
To describe the clinical, electrophysiologic, and pathologic features of EDM in a group of related Lusitano horses.
Fifteen Lusitano horses.
Neurologic examinations were conducted, and serum vitamin E concentrations were measured. Three neurologically abnormal horses were further evaluated by ophthalmologic examination, electroretinography, electroencephalography, muscle and nerve biopsies, and post-mortem examination.
Six horses appeared neurologically normal, 6 were neurologically abnormal, and 3 had equivocal gait abnormalities. Abnormal horses demonstrated ataxia and paresis. An inconsistent menace response was noted in 4 neurologically abnormal horses and in 1 horse with equivocal findings. All horses had low serum vitamin E concentrations (<1.5 ppm). Ophthalmologic examinations, electroretinograms, electroencephalograms, and muscle and peripheral nerve biopsies were unremarkable in 3 neurologically abnormal horses. At necropsy, major neuropathological findings in these horses were bilaterally symmetric, severe, neuro axonal degeneration in the gracilis, cuneatus medialis, cuneatus lateralis, and thoracicus nuclei and bilaterally symmetric axonal loss and demyelination mainly in the dorsolateral and ventromedial tracts of the spinal cord. A diagnosis of EDM was made based on these findings. Pedigree analysis identified 2 sires among the affected horses.
Conclusions and Clinical Relevance
Equine degenerative myeloencephalopathy is a neurodegenerative disorder that causes ataxia and, in severe cases, paresis, in young Lusitano horses. The disease appears to have a genetic basis, and although vitamin E deficiency is a common finding, low serum vitamin E concentrations also may occur in apparently unaffected related individuals.