Pigment retinopathy in warmblood horses with equine degenerative myeloencephalopathy and equine motor neuron disease

Vet Ophthalmol. 2017 Jul;20(4):304-309. doi: 10.1111/vop.12417. Epub 2016 Aug 5.

Abstract

Objective: A pigment retinopathy has been reported in adult horses with equine motor neuron disease (EMND) arising from chronic α-tocopherol (α-TP) deficiency. A pigment retinopathy has not been identified in horses with neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) that affects genetically susceptible young horses with α-TP deficiency. The objective of this report is to describe, for the first time, a pigment retinopathy in a family of α-TP-deficient Warmbloods (WB) with clinically apparent NAD/EDM or EMND.

Animals and procedures: Twenty-five WB horses from one farm underwent complete neurologic and ophthalmic examinations and serum α-TP concentrations were assessed. Two of the most severely ataxic horses were euthanized and postmortem examinations performed.

Results: Alpha-TP deficiency was widespread on this farm (22 of 25 horses). Eleven of 25 horses were clinically normal (age range 2-12 years), one had signs of EMND (6 years of age), 10 had signs of ataxia consistent with NAD/EDM (1-10 years), and two of these were postmortem confirmed concurrent NAD/EDM and EMND. A pigment retinopathy characterized by varying amounts of granular dark pigment in the tapetal retina was observed in four clinically apparent NAD/EDM horses (two postmortem confirmed concurrent NAD/EDM and EMND) and one horse with clinical signs of EMND.

Conclusions: A pigment retinopathy can be present in young α-TP-deficient Warmblood horses with clinical signs of EMND as well as those with signs of NAD/EDM.

Keywords: horse; lipofuscin; neurodegeneration; retina; tocopherol; vitamin E.

MeSH terms

  • Animals
  • Brain Diseases / diagnosis
  • Brain Diseases / veterinary*
  • Female
  • Horse Diseases / diagnosis*
  • Horse Diseases / pathology
  • Horses
  • Male
  • Motor Neuron Disease / diagnosis
  • Motor Neuron Disease / pathology
  • Motor Neuron Disease / veterinary*
  • Neurologic Examination / veterinary
  • Pedigree
  • Pigments, Biological*
  • Retinal Diseases / diagnosis
  • Retinal Diseases / pathology
  • Retinal Diseases / veterinary*
  • Vitamin E Deficiency / diagnosis
  • Vitamin E Deficiency / pathology
  • Vitamin E Deficiency / veterinary*
  • alpha-Tocopherol / blood

Substances

  • Pigments, Biological
  • alpha-Tocopherol