What Does It Mean if My Dog Is a Carrier of PRA?
PRA is an inherited disease, which means a dog is born with a defective gene. In some breeds, like Mastiffs and Bullmastiffs, PRA seems to be a dominant gene. That means a dog only needs to inherit one copy of the defective gene to develop the disease. In other breeds, like Samoyeds and Siberian Huskies, the gene seems to be linked with the sex of the dog and is found mainly in males.
However, in most cases of PRA, the dog needs to inherit the defective gene from both parents before developing the disease. This is known as an autosomal recessive pattern. That means dogs with only one copy of the gene for PRA won’t have PRA itself; they will carry the gene and can potentially pass it down to the next generation. These dogs are known as carriers. As Dr. Klein says, “Carriers may not have any signs of impaired vision but carry the gene, and when crossed with another carrier, they can produce affected individuals, other carriers, and possibly unaffected dogs.”
These signs may not be apparent until later in the disease, as dogs will naturally acclimate to their vision loss. Signs may be more noticeable at night or when the dog is in a new environment.
Clinical signs may include the following:
Diagnosis of Progressive Retinal Atrophy in Dogs
You may notice that your dog is not so adventurous and hesitates about jumping down from any height as he cannot judge the distance anymore. Or you may notice your dog bumps into things around the house, especially if you move the furniture. Usually by the time you notice this change in behavior, the disease has progressed to an advanced stage. As the day vision deteriorates you will notice a white opaqueness forming in the centre of the pupil, this is the cataract forming and further reducing the day vision of your canine friend.
If you suspect your dog is losing his eyesight, you need to contact your veterinarian who will refer your dog to a veterinary ophthalmologist to perform some tests on the eyes. The usual method to diagnose any abnormalities in your dog’s eye is the electroretinogram (ERG). This test measures the response of the retina to light. This test can prove conclusively that your dog has this disease. Luckily there is no pain for your dog, it will just take a bit of adjusting to getting around and your pet will appreciate your support. Make sure that he can come to no harm outside by shutting the gates to your pool or your property so keep him safe.