What is prcd-PRA?
Progressive rod-cone degeneration - Progressive Retinal Atrophy, (prcd-PRA), is a genetically controlled disease sometimes present in Entlebuchers. This disease, something like Age Related Macular Degeneration in humans, causes the retina to degrade over time, leading to blindness, often in both eyes.
prcd-PRA is an Autosomal Recessive disorder, meaning that two copies of the mutated gene are necessary to cause the disease. One copy comes from the dam (mother) and the other from the sire (father).
Symptoms of prcd-PRA
This disease causes vision loss. Eye exams may find evidence as early as 1.5 years but noticeably vision loss is generally at 3 to 5 years of age. Initially, rod disintegration will create vision deficits in dim lighting and peripheral vision. Over time, vision is impaired even in bright light, and eventually the dog becomes totally blind.
Blind dogs generally adapt very well,
and continue to live full lives, but their genes will carry this illness to potential offspring.
Before genetic testing was available, dogs were often bred before evidence of vision loss appeared. Puppies born to parents suffering PRA vision loss would have at least a 50% chance of inheriting the disease. If both parents were later found to be affected, all of the pups would go on to develop this type of blindness.
With advances in genetic science, this type of blindness can now be prevented.
Preventing PRA Blindness
With genetic testing, we can now prevent the prcd-PRA disease from causing blindness through a simple cheek swab or blood sample test. DNA in sloughed cheek cells or blood are analyzed for the gene responsible for the disease as specialized labs. The cost of a test is less than $50.
Now that we can determine the gene status before breeding, we can prevent this type of blindness. Before testing, it wasn't so easy as breeding and pups were well established before the disease presented itself with symptoms.
Say "p" represents the mutated gene and "P" represents the healthy gene; then pups with "pp" have prcd-PRA and become blind, pups with "pP" or "Pp" are carriers of the mutation, but healthy themselves and pups with "PP" are healthy.
If both dogs are healthy, "PP", then only healthy pups will be born.
If both dogs are affected, "pp", then only affected pups will be produced.
If one dog is affected "pp" and the other is healthy "PP", the pups will be 100% "Pp" , carriers.
If two carriers are bred, "Pp", the pups will be 50% "Pp" carriers, 25% healthy "PP" and 25% affected "pp".
In order to prevent blindness caused by this disease, we no longer breed dog pairs who are both carriers, and we do not breed any affected dogs.
The status of Entlebuchers can be checked through the OFA website, which lists all medical test results submitted for the dog.