Progressive Retinal Atrophy (PRA)
Progressive Retinal Atrophy (PRA) is actually several conditions which can affect your dog’s vision, leading to eventual blindness. Each of the different types of PRA act a little differently, and differ in which dogs are most susceptible. This is a discussion of some of the most common varieties of Progressive Retinal Atrophy.
Progressive Rod-Cone Degeneration (prcd-PRA)
Progressive Rod-Cone Degeneration (prcd-PRA) is by far the most prevalent of the Progressive Retinal Atrophy diseases, affecting many different breeds of dog. Breeds known to suffer from this malady include:
- American Eskimo Dog
- Australian Cattle Dog
- Australian Shepherd
- Chesapeake Bay Retriever
- Chinese Crested
- Cocker Spaniel
- English Cocker Spaniel
- Entlebucher Mountain Dog
- Finnish Lapphund
- Giant Schnauzer
- Golden Retriever
- Labrador Retriever
- Norwegian Elkhound
- Nova Scotia Duck Tolling Retriever
- Portuguese Water Dog
- Silky Terrier
- Spanish Water Dog
- Swedish Lapphund
- Yorkshire Terrier
Additionally, some popular “Designer” dogs are known to be susceptible, including the Cockapoo, the Golden Doodle, the Labradoodle, and the Maltipoo.
Progressive Rod-Cone Degeneration, as its name implies, involves the late onset degeneration of the rod and cone cells, starting with the rod cells. The rod cells are responsible for night vision, so night blindness is often the first visible symptom you see.
As the rod cells die off, the retina becomes saturated with oxygen, too much for the cone cells needs. Therefore, conditions become toxic and the cone cells also begin to die off, resulting in total blindness.
While prcd-PRA is inherited, it is inherited as a recessive trait, meaning both parents must have the disease gene. Genetic testing can determine if your dog is normal (no disease gene present at all), carrier (one of the two disease genes present) or affected (both disease genes present). To prevent spreading the prcd-PRA condition, it is important that at least one of the parents was tested and proved to be normal.
Rod-Cone Degeneration Type 4 (rcd4-PRA)
Rod-Cone Degeneration Type 4 (rcd4-PRA) is another late onset PRA mutation discovered by the Animal Health Trust in the UK. Breeds known to suffer from this malady include:
- Australian Cattle Dog
- English Setter
- Gordon Setter
- Irish Setter
- Irish Red and White Setter
- Polish Lowland Sheepdog
- Small Munsterlander Pointer
- Standard Poodle
- Tibetan Terrier
While a different mutation of the genetic makeup is responsible for rcd4-PRA, the progression and inheritance factors are similar to prcd-PRA.
Rod-Cone Degeneration Type 1 (rcd1-PRA)
Rod-Cone Degeneration Type 1 (rcd1-PRA) differs from most of the PRA mutations in that it is an early onset disease. Puppies will begin showing signs of night-blindness by the time they are six weeks old, and will usually be totally blind before they are two years old. Irish Setters and Irish Red & White Setters may be susceptible to this mutation.
Just like almost all PRA mutations, rcd1-PRA is a recessively inherited disease, requiring both parents to be carrying at least one mutated gene. Breeding should only occur if at least one of the parents has been genetically tested as clean.
Rod-Cone Degeneration Type 2 (rcd2-PRA)
Rod-Cone Degeneration Type 2 (rcd2-PRA) is yet another early onset PRA disease. Puppies will begin showing signs of night-blindness by the time they are six weeks old, and most will be totally blind before they are a year old. Collies are known to be susceptible to this mutation.
Just like almost all PRA mutations, rcd2-PRA is inherited recessively. Since both parents must be carrying a mutated gene to result in the puppy acquiring this disease, at least one parent that has been genetically tested as clean should be used for breeding.
Rod-Cone Degeneration Type 3 (rcd3-PRA)
Rod-Cone Degeneration Type 3 (rcd3-PRA) is also an early onset PRA disease affecting the Cardigan Welsh Corgi and the Chinese Crested. Progression and inheritance is similar to rcd2-PRA.
As you may have guessed from the name, this mutation occurs only in the Basenji breed. It is normally first diagnosed at five years old, and will progress gradually, eventually resulting in total blindness.
Similar to most varieties of Progressive Retinal Atrophy, Basenji PRA is inherited as a recessive trait, meaning both parents have to supply the mutated gene in order for the dog to be infected. Therefore when breeding make sure at least one of the parents has been tested normal, with no mutated gene.
Dominant PRA is the only mutation of the PRA disease that is a dominant inheritance. This means that if even one of the parents has the mutation, chances are extremely likely that the puppies will receive the mutation, and will be affected. only one affected gene is required to have the disease, instead of requiring both as in other mutations.
The Bullmastiff and the Mastiff are both susceptible to this disease. In addition to the normal late onset progression of this disease, it is important to know that dogs affected are also susceptible to further retinal damage if exposed to bright lights. Ophthalmological exams should only be done using infrared, and exposure to bright sunshine should be avoided.
There are various genetic mutations which can cause Progressive Retinal Atrophy. There is no cure for PRA, so the only thing we can do about it is responsible breeding to eliminate the mutations from future generations of dogs.
But don’t worry about your dog! She will develop her other senses as she slowly goes blind. It is far worse on you than her, believe me!
Want to learn more?
Because of her work in a ophthalmic veterinary clinic, Caroline Levin had the opportunity to meet many blind and low vision dogs and get many tips from their owners. From these discussions, Living With Blind Dogs: A Resource Book and Training Guide for the Owners of Blind and Low-Vision Dogs, Second Edition was born. Now in its second edition, even more information on living with a blind dog is included.
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