Progressive retinal atrophy is a hereditary health condition that affects a significant number of different breeds and types of dogs, by means of genetic inheritance through the breed line. It affects the eyes of the dog by means of causing a gradual degeneration in the eye tissues, which ultimately causes blindness.
The condition cannot be caught or transferred from dog to dog other than by means of heredity, and this means that in order to prevent the condition from being passed on to ever more dogs and spreading widely throughout the affected breeds, potential breeding stock from at-risk breeds should be tested first, to ensure that they will have the best possible chance of producing healthy puppies.
Progressive retinal atrophy comes in a wide range of different variants, all of which lead to blindness by means of different methods-and whilst the end result is the same, the different forms that the condition takes means that a different test is required for each one-and also, that each form of the condition has different sets of breeds that are at risk for that particular variant.
The Kennel Club and the British Veterinary Association run a wide range of health schemes in order to monitor and attempt to curb the spread of common hereditary health conditions, and part of this scheme means testing for the CRD3 variant of progressive retinal atrophy.
In this article, we will talk more about the CRD3 form of the condition, and how to get your own dog tested for it. Read on to learn more.
The CRD3 variant of progressive retinal atrophy is a specific form of the condition that falls under the main umbrella of the condition as a the whole. The CRD3 designation refers to cone-rod dystrophy that leads to a progressive and gradual dystrophy of the eye’s cones, the retinal cells that enable the dog to see in normal daylight. In turn, the rods of the eyes, responsible for night vision and being able to see in dim light and darkness begin to degenerate as well.
PRA (CRD3) is particularly prevalent across the gene pool of the Glen of Imaal terrier, and is in fact largely unique to this one breed of dog. However, it is important to note that cross breeds and mongrels that have Glen of Imaal Terrier ancestry or part-breeding may also inherit the condition as well.
If you own a Glen of Imaal terrier and plan to breed from them, it is important to get them tested first to ensure that they are not carrying the condition. Even if you do not intend to breed from your dog, it may be worthwhile testing your dog anyway so that you know what to expect, and the same is true for the owners of part-bred dogs with some Glen of Imaal Terrier ancestry.
The condition’s eventual progression to blindness is a slow one, and dogs younger than three years of age rarely exhibit the symptoms of the condition, and may appear ostensibly normal and healthy until they get older.
Once the condition does begin to manifest, you will begin to notice the signs of a gradual deterioration in your dog’s general vision, which may first become apparent in the dark and in dim lighting.
PRA (CRD3) is an autosomal recessive condition, which means that if a dog only inherits the gene that carries the condition from one of their parents but not the other, they will not suffer from eventual blindness themselves, but will be a carrier for the condition and run the risk of passing it on to their own offspring.
Dogs that inherit two genes for PRA (CRD3) (one from each parent) will be afflicted with the condition, whilst dogs bred from parents that were both clear of the condition will not inherit progressive retinal atrophy, nor become a carrier for it.
In order to diagnose PRA (CRD3) or the markers for it that indicate that the dog is a carrier but not affected by it themselves, a DNA test is required.
This usually involves simply taking your dog along to your local vet and having them take a DNA sample from your dog by means of swabbing the inside of their cheek, and this sample is then sent off to a laboratory that can interpret it, and provide the results.
For a list of the laboratories that can perform the appropriate test, check out this list of The Kennel Club’s authorised laboratories-or talk to your local vet, as they may already have a working relationship with a local laboratory and be able to send off the sample on your behalf.