by Stephanie Dixon
It has come to the attention of the Barbet community that the prcd form of PRA is a disease that we have to be on the lookout for in our breed. “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. “prcd” stands for “progressive rod-cone degeneration” which is a type of PRA known in several breeds.” Typically a late onset disease, dogs with prcd-PRA will often not show any symptoms until long after they have been used in breeding programs. It does not cause physical pain for the dogs but certainly blindness is something that we wish to avoid producing.
The Optigen website states that “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.” The genetic test for prcd indicates whether or not the dog is normal/clear, a carrier or affected/ at risk. Dogs that are normal/clear are not at risk for developing the disease and can be bred to any dog since they will not pass on the gene. Dogs that are a carrier are again not at risk but could pass on the gene for prcd to their offspring and should only be bred to a dog that is normal/ clear in order not to produce any affected offspring that would then be at risk for developing PRA. Dogs whose results come back showing that they are affected / at risk have a very high likelihood of developing the prcd form of PRA, they should only be bred to dogs that are normal/clear.
Prior to this spring I had not heard of any Barbets being tested for prcd-PRA nor had I heard of any that had been diagnosed with the disease. However, now that more Barbets are getting DNA testing done with MyDogDNA and Embark and obtaining results for a large numbers of diseases, we are gathering more information about the health of our Breed. In fact it was through testing with Embark’s comprehensive panel of 160 diseases that it became known to breeders that the form of prcd-PRA was in the Barbet.
In July 2017, MyDogDNA reported that “According to our scientific research, we have discovered that in >100 tested barbets, prcd-PRA occurs in 13 % of the population.” Here you can find more information. If you have already tested your Barbet with MyDogDNA, the prcd-PRA test is available as an add on for an additional fee of over $200, making Embark a much better full panel value. Alternatively you can send off for a test kit from another lab such as GenSol that frequently offers discounts for the stand alone prcd-PRA test.
EmbarkVet had their science team run an analysis in July 2017 and they were able to share that based on the dogs in their database, “The mutation is at a frequency of about 12.5%.” (Alli Kendrick, EmbarkVet). At that time they were aware of 2 carriers and one affected Barbet. By the end of October that number had grown by at least two more carriers and the carrier rate was reported by Embark as being 15%. As owners continue to test their dogs and share the results we will be able to get a better picture of how prevalent the disease is within our breed.
Dr. David Silversides DVM, PhD. at the Laboratory of Veterinary Genetics, Faculty of Veterinary Medicine University of Montreal has been very helpful. He believes that based on the data obtained by MyDogDNA, and despite the fact that the number of Barbets tested to date is not high, carrier rates for the Barbet may be about 1 in 7.
Moving forward I strongly recommend that all breeders include testing for the prcd form of PRA as part of their pre-breeding health testing. As mentioned earlier, the test for prcd-PRA can be obtained as a stand alone test from many different labs and for those doing the EmbarkVet tests it is included in their disease panel.
A word of caution for Barbet breeders; DNA testing allows us to maintain as much diversity in our already small gene pool as possible by enabling us to continue to use carrier and even affected dogs in our breeding programs without the risk of producing affected puppies. If breeders choose to breed only dogs that are clear to one another and/ or if they choose to only keep the puppies in the litter that are clear they run the very real risk of eliminating dogs that may end up testing clear on a future DNA test for a different disease.