Abstract
Abstract: :
Purpose: To study hemeralopia found in clinical cases of the wirehaired dachshund breed of dog. Methods: Two clinically normal daughters from a combination of a hemeralopia affected male and two unrelated dams of another breed were backcrossed to their hemeralopia affected father. The offspring were examined clinically and full-field electroretinograms (ERGs) were performed at the age of eight weeks. Two affected pups plus one unaffected littermate were euthanized at the age of 3 months and the eyes processed for light- (LM) and electron microsocpy (EM) and immunohistochemistry (IHC). Antibodies against cells in the inner retina, cones and glial cells were used in the IHC study. Results: Of 14 offspring obtained, five showed signs of hemeralopia: one female in one litter, two females and two males in another. Clinical signs were present from 4 to 12 weeks of age, with normal appearing fundi. Electroretinography showed absence of scotopic 30 Hz flicker responses in all clinically affected dogs. IHC showed reduced numbers of blue sensitive cones in affected animals. LM and EM demonstrated abnormal appearing nuclei, outer and inner segments of the cone photoreceptors specifically. Conclusions: This study shows that hemeralopia is an inherited retinal disease of wirehaired dachshunds with early onset functional and structural changes of the cone system. This strain of dog has the potential to become a new animal model for human cone dystrophies.
Keywords: retinal degenerations: hereditary • animal model • retina: distal(photoreceptors, horizontal cell