Progressive retinal atrophy is one of the most common hereditary eye conditions that can affect dogs, and that is prevalent within certain breeds, passed on through the genes to each successive generation of dogs.
Progressive retinal atrophy cannot be prevented or cured in dogs that inherit the faulty genes that cause the condition, and whilst it is painless for dogs that are affected, it ultimately leads to total and irreversible blindness, making it a significant threat to the health and quality of life of dogs affected by it.
Progressive retinal atrophy comes in many different variant forms, each of which ultimately have the same effect-causing the dog to lose their sight-but each of the different forms affect the eyes in various different ways, and are caused by different gene mutations.
Understandably, having a significant number of dogs of one breed that carry the mutation for progressive retinal atrophy means that the condition will become widespread within that breed, and the only way to prevent its ongoing spread and the number of dogs affected by it in the future is to remove affected dogs from the gene pool, by not using them to breed from.
This means that in breeds that have particularly high occurrence rates of the condition, genetic testing is strongly advised, in order to allow dog owners to get a complete picture of the health of their dog’s eyes and so, make an informed decision on whether or not to breed from them.
Because each variant of progressive retinal atrophy is caused by a different gene mutation, the test required for each variant is different-and in this article, we will look at the GPRA rcd4 variant of progressive retinal atrophy, which is most common within the Irish setter and Gordon setter dog breeds.
Read on to find out more about the condition, how it is tested for, and why testing is so important.
The name GRPA rcd4 stands for “generalised progressive retinal atrophy, rod-cone degeneration four,” which means that this variant of progressive retinal atrophy affects both eyes by destroying the rods and cones at the back of the retina, the cells that are responsible receiving and interpreting light and colour.
Over time, this leads to a complete and irreversible blindness in affected dogs, which while not painful, obviously significantly affects the dog’s quality of life. You can find out more about progressive retinal atrophy in general by reading this article.
GPRA rcd4 is a hereditary condition that is particularly commonly found in the gene pools of the Irish setter and Gordon setter, and of course, potentially any cross-breed and mongrel dogs that have ancestry from these two breeds.
Unlike many of the other variants of progressive retinal atrophy, GRPA rcd4 is notable because it is generally a late-onset form of the condition, rarely becoming apparent in dogs before they reach the age of ten-although there are of course some exceptions.
This means that unlike other forms of the condition that progress faster, dogs have often reached old age by the time they are diagnosed with the condition, and may have already been used for breeding, which is why testing for the condition prior to breeding is so important.
GRPA rcd4 is caused by a single recessive mutated gene called rcd4, which means that in order for a dog to develop the condition themselves, they need to inherit two copies of the mutated gene, one from each parent.
A dog that only inherits one copy of the mutated gene along with one healthy gene will not exhibit the condition themselves; but they will become carriers for it, and pass the heredity onto their own offspring. The third generation then will vary in terms of their expression of the condition-on average, 25% of the third generation will be clear of the condition, 50% will become carriers themselves, and 25% will be both carriers and affected by the condition.
Testing potential breeding stock of the Irish setter or Gordon setter breeds for the presence of the GRPA rcd4 gene mutation is particularly important, because the condition usually does not present until old age, by which time many dog owners will have come to conclude that their dogs are not going to be affected by it.
A DNA test is necessary in order to identify the faulty gene, and these tests can be carried out at one of several laboratories that offer it, by means of testing a cheek swab sample from the dog in question.
The swab can be taken by your dog’s own local vet and then sent off for testing-for information about The Kennel Club’s approved laboratories that can run the test, check out this list.