The term "PRA" refers to 'Progressive Retinal Atrophy," which is a group of disorders in which cells in the retina of the eye degenerate, eventually leading to vission loss. One form of PRA occurs in Cardigan Welsh Corgis, known as rcd3-PRA. In this form of PRA, the rod cells of a young Corgi begin to die, often before the age of 1 year old. The rod cells are responsible for vision in low-light or night settings and the dog quickly becomes night-blind. At 2-3 years old, the dog's cone cells also degenerate and die off. This leads to a loss of color vision as well as well as vision in bright light. This ultimately results in complete blindness. Unfortunately, there is no cure for PRA.
Because rcd3-PRA is a recessive disorder, a dog can be an obligate carrier and not display any symptoms of the disease. This makes DNA testing an important tool to ensure the health of all puppies. Breeding two carrier dogs can result in affected offspring. There is a 25% chance that a pup could receive the mutated allele from each parent and be affected by the disease.
Petersen-Jones SM, Entz DD, Sargan DR. cGMP phosphodiesterase-alpha mutation causes progressive retinal atrophy in the Cardigan Welsh corgi dog. Invest Ophthalmol Vis Sci. 1999 Jul; 40(8):1637-44. [PubMed: 10393029]
Petersen-Jones SM, Zhu FX. Development and use of a polymerase chain reaction-based diagnostic test for the causal mutation of progressive retinal atrophy in Cardigan Welsh Corgis. Am J Vet Res. 2000 Jul; 61(7):844-6. [PubMed: 10895911]
Petersen-Jones SM, Entz DD. An improved DNA-based test for detection of the codon 616 mutation in the alpha cyclic GMP phosphodiesterase gene that causes progressive retinal atrophy in the Cardigan Welsh Corgi. Vet Ophthalmol. 2002 Jun;5(2):103-6. [PubMed: 12071867]
|P/P||Affected: Dog has two copies of the PRA-rcd3 mutation and will be affected. The mutation will always be passed on to every offspring.|
|n/P||Carrier: Dog carries one copy of the mutation associated with PRA-rcd3. Dog will not be affected by PRA-rcd3 but may pass the mutation to offspring.|
|n/n||Clear: Dog is negative for the mutation associated with rcd3-PRA.|