The OptiGen prcd-PRA Test
Breed specific information:
The genetic disorder, prcd-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. 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.
Unfortunately, at this time there is no treatment or cure for PRA. If your dog is affected, you may find it helpful to read about other owners’ experiences living with blind dogs. (suggested links:www.eyevet.org and www.blinddogs.com)
Prcd-PRA is inherited as a recessive trait. 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.
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.
Although prcd-PRA is inherited, it can be avoided in future generations by testing dogs before breeding. Identification of dogs that do not carry disease genes is the key. These "clear" dogs can be bred to any mate - even to a prcd-affected dog which may be a desirable breeding prospect for other reasons. The chance of producing affected pups from such breedings depends on the certainty of test results. Again, you’ll find the specific information on certainty of test results for your dog by linking to breed specific information.
The OptiGen prcd test is done on a small sample of blood from the dog. The test analyzes the specific DNA mutation causing prcd-PRA. The OptiGen test detects the mutant, abnormal gene copy and the normal gene copy. The result of the test is a genotype and allows separation of dogs into three groups: Normal/Clear (homozygous normal), Carrier (heterozygous) and Affected (homozygous mutant).
|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 affecteds
|Heterozygous||Carrier||Should be bred only to Normal/|
Clear to remove risk of producing
|Homozygous Mutant||Affected||Should be bred only to Normal/|
Clear to remove risk of producing
The prcd-PRA test is done on a small sample of blood obtained by your veterinarian. This allows the lowest risk of contamination of the sample and added assurance of a match of the sample with the identified dog. Please read Instructions and Information to learn about ordering a test, shipping a sample and prices.
Affected dogs are tested at no charge. Please review the conditions for this before submitting a sample from an affected dog.
Registries: Breed clubs may sponsor genetic disease registries and OptiGen may provide some test information directly to the registry in accordance with the club’s official policies. Please go to your club to learn more about this.
The research leading to this discovery was undertaken by scientists at the James A. Baker Institute of Animal Health at Cornell University's College of Veterinary Medicine in Ithaca, New York. Initial data are published in volume 95 of the March, 1998 issue of the Proc. National Academy of Sciences. Publication of the prcd mutation is being prepared. The patented technology underlying this test is under exclusive license to OptiGen from Cornell Research Foundation, Inc.