Retinal Dysplasia in English Cocker Spaniels

Retinal dysplasia is an eye disease affecting the retina, which leads to severe visual impairment and even to total blindness. The disease causes retinal development disorders, retinal hemorrhages and complete or partial retinal detachment. Clinical signs appear in puppies. Affected dogs show significant visual impairment, disorientation in unfamiliar surroundings, loss of pupillary reflex and reaction to glare, wandering eye movements, dark-colored irises and intraocular hemorrhages.

The cause of the disease is the c.653_654insC mutation in the NDP gene, which causes shortening and dysfunction of a protein essential for the normal development of the vascular and nervous system of the retina.

The mutation is X-linked recessive. This means that it is located on the X chromosome. Since the genotype of males is composed of X and Y chromosomes, they can only be healthy (not affected by the mutation) or affected. The genotype of females contains two X chromosomes, so females can be either healthy, carriers or affected. Carriers usually do not show clinical signs, but they are able to pass the mutated allele on to their offspring.

A genetic test can clearly reveal the genotype of the animal and is a suitable tool for breeders to avoid unintentional breeding of affected puppies.

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Reference:

Joyce, H., Burmeister, L.M., Wright, H., Fleming, L., Oliver, J.A.C., Mellersh, C. : Identification of a variant in NDP associated with X-linked retinal dysplasia in the English cocker spaniel dog. PLoS One 16:e0251071, 2021. Pubmed reference: 33945575