Abbreviated Name: PRA

Disease Description: A disease where the retina slowly deteriorates, producing night blindness.

Inherit Mode: In the Siberian husky, PRA is an X-linked trait. In most breeds studied to date, PRA is inherited as an autosomal recessive trait.

Disease Symptom: Generalized PRA - early onset: The first sign is generally failing night vision, as early as 6 weeks of age, and this progresses to complete loss of vision by about 1 - 2 years of age. Collies may retain some vision until the age of 2 - 3 years. In miniature schnauzers, poor night vision usually develops later (6 months to a year) and there is advanced loss of vision by 3 to 4 years. Affected Alaskan malamutes are day-blind (hemeralopia) at 8 to 10 weeks of age; night vision is never affected. Generalized PRA (progressive rod-cone degeneration) - late onset: Generally night blindness is noticed between 2 and 5 years of age (depending on the breed) progressing to total blindness within a year or so. Peripheral vision is lost first. Central PRA (CPRA) - retinal pigment epithelial dystrophy (RPED):Loss of vision occurs much more slowly than in generalized PRA, without initial night blindness. Affected dogs may not lose vision completely. Because the changes are in the centre of the retina, affected dogs initially have trouble locating still objects in bright light.

Disease Cause: -

Disease Diagnose: There are no obvious external changes to the eyes. You may notice that your dog has difficulty getting around when the lights are turned off, or when outside at night. If you suspect that your dog has impaired vision, your veterinarian will look for abnormalities with an ophthalmoscope. PRA may also be detected by electroretinogram(ERG) before your dog has any apparent visual difficulties. Electroretinography, which measures electrical patterns in the retina, is usually only available in specialty veterinary centres. (See CERF website listed in references below.) Genetic testing is quickly becoming available for different forms of PRA in different breeds. The advantage of such testing is that it can identify dogs whose sight is unaffected, but who are carriers of the disorder (heterozygotes).

Treat Method: There is no treatment for PRA. The degree of visual impairment varies with the breed and specific type of retinal degeneration as described above, but most affected dogs will ultimately be completely blind. With their acute senses of smell and hearing, dogs can compensate very well, particularly in familiar surroundings, to the point where owners may be unaware of the extent of vision loss. You can help your dog by developing regular routes for exercise, maintaining consistent surroundings, introducing any necessary changes gradually, and being patient.

Breeder Advice: Breeding is not advised for any dog with PRA, or for the parents (assumed to be carriers). Siblings should be carefully screened by electroretinogram if they are considered for breeding. Generalized PRA can often be detected by electroretinography at least a year before clinical signs are apparent. For some disorders (eg. rod-cone dysplasia type I in Irish setters), blood-based DNA tests are available which can distinguish normal animals from those who are clinically normal but are carriers, and from those that are affected but are not yet showing any signs. Test results are registered through the Canine DNA Registry administered by the Canine Eye Registration Foundation (CERF). DNA testing for PRA is also available for Chesapeake Bay retrievers, Labrador retrievers and Portuguese water dogs. For more information see the resources below.

Disease Description Source: Link