Clinical findings in early onset cone-rod dystrophy in the Standard Wire-haired Dachshund.
OBJECTIVE
To describe the clinical findings and the age of onset of cone-rod dystrophy (crd) in the Standard Wire-haired Dachshund (SWHD) and to evaluate which clinical tests could be used to obtain a reliable diagnosis.


METHODS
Sixty-eight SWHD and SWHD-derived dogs were used, including 23 affected with crd and 45 controls, respectively.


METHODS
The dogs were subjected to behavioral testing, examination of pupillary light reflexes (PLRs), indirect ophthalmoscopy and bilateral full field electroretinography (ERG).


RESULTS
The majority of affected puppies (5-10 weeks) displayed pin-point sized pupils upon examination with focal light. All dogs in the control group, except one, displayed normal PLRs upon examination. In all crd-affected dogs there was a great variation both in age of onset and in clinical appearance of retinal changes upon fundoscopy. Two siblings displayed panretinal degeneration at the age of 10 months while other affected dogs showed early changes at the age of 3 years. Generalized bilateral retinal atrophy was the end stage of the disease. The maze test revealed no obvious differences among affected and unaffected groups. ERG recordings showed only slightly reduced rod, and mixed rod-cone responses, but severely reduced cone single flash a- and b-wave amplitudes, and cone flicker amplitudes were observed in all affected dogs.


CONCLUSIONS
Presence of pin-point sized pupils in young SWHDs was found to be an important indicator of early onset crd. Fundoscopic changes and progression of disease at later stages resembled those previously described in the majority of progressive retinal atrophies in dog. ERG was found to be the most reliable diagnostic procedure to clinically diagnose crd in the SWHD.
Ropstad
Ernst O
EO
Department of Companion Animal Clinical Sciences, Norwegian School of Veterinary Science, Oslo, Norway. ernst.ropstad@veths.no
Bjerkås
Ellen
E
Narfström
Kristina
K
D000818:Animals; D000831:Animals, Newborn; D003941:Diagnostic Techniques, Ophthalmological / Q000662:veterinary; D004283:Dog Diseases / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D004285:Dogs; D004596:Electroretinography / Q000662:veterinary; D005260:Female; D020022:Genetic Predisposition to Disease; D008297:Male; D010375:Pedigree; D012174:Retinitis Pigmentosa / Q000175:diagnosis / Q000662:veterinary*