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Progressive Retinal Atrophy (Discovered in the Basenji)

Progressive retinal atrophy (PRA) is an eye disorder where the light sensing retina at the back of the eye degenerates, causing progressive vision loss and eventual blindness.

Key Signs

Progressive vision loss, Night blindness, Reduction of the visual field (tunnel vision), Blindness

Age of Onset

3 to 7 yrs

Adult to mature onset

Inheritance

Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

Moderate-high likelihood

At risk dogs are likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with PRA

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about PRA

In Basenjis, the initial clinical signs of PRA are caused by degeneration of rod photoreceptor cells resulting in loss of night vision, followed by reduction of the visual field. Gradual progression of daylight blindness occurs as the cone cells of the retina also degenerate. Signs of disease include variable reflectivity of the tapetum and attenuated blood vessels. The onset of signs occurs in adulthood, typically at 5-6 years of age. Affected dogs usually retain adequate daylight vision for many years, sometimes throughout their natural lifespan. Affected dogs usually adjust well to their normal surroundings despite the reduction of visual field and night blindness.

Although this condition results in gradual vision loss, and possible complete blindness, many dogs adapt remarkably well to vision loss. However, some dogs may exhibit a tentativeness when introduced to unknown environments, especially in low light conditions, because their vision is compromised. Occasionally, they may react abruptly (snapping) if they are startled so caution and use of verbal queues should be taken when handling a blind dog. Caretakers should take precautions to protect the blind dog from threats it cannot detect (ex. cliffs, sharp points on furniture, moving vehicles). Owners may find that it is helpful to keep the dog's main environment as stable as possible (avoid moving furniture, etc.) to help them navigate as vision worsens.

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the PRA mutation can be safely bred with a clear dog with no copies of the PRA mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the PRA mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the PRA mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene SAG
Variant T>C
Chromosome 25
Coordinate 44,843,440

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Goldstein, O., Jordan, J. A., Aguirre, G. D., & Acland, G. M. (2013). A non-stop S-antigen gene mutation is associated with late onset hereditary retinal degeneration in dogs. Molecular Vision. 19:1871-84. View the article