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Health > Eyes > Progressive Retinal Atrophy (PRA)

The genetic disorder Progressive Retinal Atrophy (PRA), causes cells in the retina at the back of the eye to degenerate and die, even though the cells seem to develop normally early in life.

PRA refers to a group of diseases that cause the retina of the eye to degenerate slowly over time. The result is declining vision and eventual blindness.

The acronym "prcd" stands for "progressive rod-cone degeneration" which is the type of PRA known in several breeds.  The “rod” cells operate in low light levels and are the first to lose normal function. Night blindness results. Then the “cone” cells gradually lose their normal function in full light situations. Most affected dogs will eventually be blind.

Typically, the clinical disease is recognized first in early adolescence or early adulthood. Since age at onset of disease varies among breeds, you should read specific information for your dog. Diagnosis of retinal disease can be difficult. Conditions that seem to be prcd-PRA might instead be another disease and might not be inherited. OptiGen’s genetic test assists in making the diagnosis. It’s important to remember that not all retinal disease is PRA and not all PRA is the prcd form of PRA. Annual eye exams by a veterinary ophthalmologist will build a history of eye health that will help to diagnose disease.

Cure/Treatment:None

If your dog is affected, you may find it helpful to read about other owners’ experiences living with blind dogs.

Inheritance
Prcd-PRA is inherited as a recessive trait in most cases. This means a disease gene must be inherited from each parent in order to cause disease in an offspring. Parents were either "carrier" or affected. A carrier has one disease gene and one normal gene, and is termed “heterozygous” for the disease. A normal dog has no disease gene and is termed "homozygous normal" - both copies of the gene are the same. And a dog with two disease genes is termed "homozygous affected" - both copies of the gene are abnormal.

Breeds Affected:
American Cocker Spaniel
American Eskimo Dog
Australian Cattle Dog
Australian Shepherd (Aussie)
Australian Stumpy Tail Cattle Dog
Chesapeake Bay Retriever 
Chinese Crested
English Cocker Spaniel
EntlebucherMountain Dog
Finnish Lapphund
Golden Retriever
Kuvasz
Labradoodle
Labrador Retriever
Lapponian Herder
Miniature & Toy Poodle
Nova Scotia Duck Tolling Retriever
Portuguese Water Dog
Spanish Water Dog
Swedish Lapphund

It’s been proven that all breeds being tested for prcd-PRA have the same disease caused by the same mutated gene. This is so, even though the disease might develop at different ages or with differing severity from one breed to another. To ensure your Australian Shepherd (Aussie) doesn't carry this gene have him tested.

PRA Breeding Strategies:
Potential Genotype of Offspring
Parent Genotype 2
Parent Genotype 1 Homozygous Normal (NN) Heterozygous Affected (ND) Homozygous Affected (DD)
Homozygous Normal (NN)  All Normal (NN)
1/2 Normal = NN
1/2 Hetero. Affect. = ND
All Hetero. Affect. = ND
Heterozygous Affected (ND)  1/2 Normal = NN
1/2 Hetero. Affect. = ND
1/4 Normal = NN
1/2 Hetero. Affect. = ND
1/4 Homozyg. Affect. = DD
1/2 Hetero. Affect. = ND
1/2 Homozyg. Affect. = DD
Homozygous Affected (DD) All Hetero. Affect. = ND 1/2 Hetero. Affect. = ND
1/2 Homozyg.Affect. = DD
All Homozyg.Affect. = DD

Breeder's Note: It is VERY good news knowing that if you breed a normal to a normal none of the puppies will have PRA! and even though Optigen indicates in their table that all the gray areas are acceptable breedings, as a breeder I don't think I would breed an affected or a carrier knowingly to produce puppies that are carriers of PRA. OFA will clear by parentage for first generation puppies.

prcd-PRA Breeding Strategies:
Possible results using the OptiGen prcd test
Genotype Risk Group Significance For Breeding Risk of prcd Disease
Homozygous Normal Normal/Clear Can be bred to any dog, extremely low risk of producing affected offspring
Extremely low
Heterozygous Carrier Should be bred only to Normal/Clear to remove risk of producing affected offspring Extremely low
Homozygous Mutant Affected Should be bred only to Normal/Clear to remove risk of producing affected offspring Very high

Source: Optigen

Progressive Retinal Atrophy (PRA) Testing Requirements and Costs

Rev. 15 January 18



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