Progressive Retinal Atrophy (Discovered in the Shetland Sheepdog - CNGA1 variant)

Progressive Retinal Atrophy (PRA) is a disorder that causes the degeneration of the light sensing retina at the back of the eye, resulting in vision loss and eventual blindness.

Key Signs

Degeneration of the photoreceptor cells of the retina, Night blindness, Vision loss, Blindness

Age of Onset

1 to 4 yrs

Junior to adult onset


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

Clinical signs of the disease typically appear only when the vision of the dog is already impaired. The dog may be reluctant to walk in a dark environment or up or downhill. Affected dogs may also have dilated pupils with an abnormal shine. The disease does not cause pain and there is no curative therapy. The age of onset and age of diagnosis vary between 2 to 11 years of age.

A blind dog tends to adapt well to the loss of vision. However, some dogs may exhibit a tentativeness when introduced to unknown environments 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).

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 CNGA1
Variant Deletion
Chromosome 13
Coordinate Start 43,831,900
Coordinate End 43,831,897

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Wiik, A. C., Ropstad, E. O., Ekesten, B., Karlstam, L., Wade, C. M., & Lingaas, F. (2015). Progressive retinal atrophy in Shetland sheepdog is associated with a mutation in the CNGA1 gene. Animal Genetics, 46(5), 515–521. View the article