prcd-PRA Testing Goldens--a bunch of smoke?

Jim Drager · Aug 23, 2008

Hi Melanie!

I know of two GR's that are both a) tested positive b) have diminished eyesight, and it is getting worse. Both of them are out of my Maverick, who is a "carrier" per Optigen.

I also know of 2 other GR's who have not been tested, who were bred to Mav, produced clinically affected dogs, and are "blind". Obviously, I will not disclose who they are...that is up to the owners.

I am not saying the science is real or not, but there is at least a little fire under all of the smoke.

Jim

Ps...are you coming to the Specialty so that you may join the legions of us seeking to feel "cheap in the morning" :>)

stevelow · Aug 23, 2008

This is a great discussion. Thank you, Melanie for raising the question, and thank you Gerry for filling in many of the blanks. Both of you have a lor of experience breeding Golden Retrievers, and I respect your knowledge.

I have two pertinent questions:

1. Can an exam by an ACVO determine if PRA is of the prcd variety?

2. While I realize that Optigen is bound by confidentiality, as they should be, why can't they publish statistics in a timely fashion. I would like to know how many GRs have been tested, and how many are affected or carriers.

Eric Johnson · Aug 23, 2008

There are a whole range of possibilities.

1. Goldens have something about their make-up that causes the problems to be later onset or expressed differently.

2. Golden owners don't notice the eyes issues specifically because of other health problems.

3. Somehow Golden breeders have bred away from the issue.

4.

5.

6. and so on.

It's a definitional thing. Prcd-PRA is prcd-PRA. If Goldens are different and get prcd-PRA(2), then it's wise to find out what the difference is....by testing.

I don't think a carrier bred to a carrier will produce a litter of 25% affected dogs! Instead, each puppy from a carrier to carrier breeding has a 25% chance of being affected. There is a substantial difference. The 25-50-25 ratio only works out when applied to relatively large populations.

It seems to me that the Golden owners would be testing like crazy and hoping there will be some mitigating factor. With a population of 10's of thousands whelped each year, it is far to early (with results of maybe 200 dogs) to declare this a hoax. Get 1,000 tests run and then talk to Dr. Aguirre. He's not going to lead you knowingly astray. He can only work with the facts in evidence and there just aren't enough facts yet.

It's tough (and expensive) to be the leader.

Eric

2goldens · Aug 23, 2008

Melanie, good to keep this discussion in the forefront. We cannot get definite answers until more dogs are tested and people are upfront with results. So much better to have knowledge and we can only do that with the statistics from testing.
Jim answered some questions of dogs that he knows of; there are probably more dogs out there that we do not know about.
Gerry's responses are wonderfully given and all her work is appreciated!
My wish is that at the National, more are tested!
And, Jim, I am so hoping I feel "cheap" in the morning!

Gerry Clinchy · Aug 23, 2008

stevelow said:
This is a great discussion. Thank you, Melanie for raising the question, and thank you Gerry for filling in many of the blanks. Both of you have a lor of experience breeding Golden Retrievers, and I respect your knowledge.

I have two pertinent questions:

1. Can an exam by an ACVO determine if PRA is of the prcd variety?

No. In humans, retinitis pigmentosa is analogous to PRA in dogs. In humans, there are 46 genetic causes of retinitis pigmentosa, encompassing 5 different genetic mechanisms ... for the same clinical symptoms.

This is similar to the situation with PRA in dogs.

2. While I realize that Optigen is bound by confidentiality, as they should be, why can't they publish statistics in a timely fashion. I would like to know how many GRs have been tested, and how many are affected or carriers.

You are not alone in this desire for more information more quickly

. I believe where Optigen has an established relationship with a National breed club they provide quarterly statistics to the National club.

Ann Hubbs of the GRCA Health and Genetics Committee is in touch with Optigen. I do not know if there is yet a regular mode of reporting the statistics to GRCA since the numbers examined have been relatively small (v. other breeds) and the statistics are not a good random sample.

The most recent update to the Optigen site dated 8/14/08 give us current statistics. It does not mention the exact number tested, but my best guess would be something over 400, but less than 500.

Gerry Clinchy · Aug 23, 2008

Melanie Foster said:
The question asked was "how many blind dogs" ... didn't specify prcd-PRA.

See the subject and decide what I was inquiring about.

You have presented a "Catch 22" situation. If dogs who are deceased were not tested, we cannot be sure of which type of PRA they had. However, if we find those same dogs in pedigrees of dogs today that have been found to have the prcd form of PRA, it would seem at least somewhat reasonable to suspect that those ancestors may have had the same form of PRA.

That could be an erroneous conclusion ... or not. We simply don't know.

The two now living have been dx'd by an ACVO & have tested affected with prcd-PRA by Optigen.

And where is the update as to how they're progressing?

As Jim mentioned, one dog has gradually been progressing. There are definitely certain situations where there is visual deficiency. It is up to the owners of the dogs to report this to Optigen. Optigen cannot report information they don't have. If any owner who has an affected dog does not take that responsibility, it is unfortunate, but nothing that anyone else can do about it.

The three deceased were dx'd with PRA by an ACVO.

prcd-PRA? If not, why are you mentioning them?

Because at least two of them later produced carrier-tested or affected offspring. It simply demonstrates that PRA has been around for a while, even though nobody talked much about it.

Of the two whom I'm not sure are still living, one's owner did not proceed to DNA testing (although it was available at the time); the other was not dx'd by an ACVO, but owner commented "was blind at 10" & produced an affected get & also did not proceed to DNA testing, to my knowledge.

Melanie

Melanie: I'm a little curious as to why folks are getting upset for me questioning this. I would think y'all would be wanting answers like I do.

I, for one, am not at all "upset" for you asking these questions.

I have been irritated for years by "experts" feeding us selective facts figuring we were not bright enough to accept the "holes" in various theories and could use good judgment in assessing the whole picture. To this day there are gaps in the information we are given by OFA, and even PennHIP. With some digging you can find it, but it is not easily available.

It was breeders who first noticed that pigmentary uveitis showed a disturbing familial relationship in Golden Retrievers ... before the "experts" realized this was a distinctive form of the disease in Golden Retrievers.

Owners and breeders are in the forefront of breeding healthy dogs. By realizing we are all in the same boat & sharing what we learn we can continue to do that.

If we consider this prcd-PRA testing as "research", we can "fund" the research either by sending money to GRF or some other research entity ... or we can test our dogs to get the data needed.

The advantage of the latter is that one hits two birds with one stone. First, we fund the data-gathering effort. Second, while we're waiting for the final answer of the "research" we are hopefully able to avoid producing any blind dogs. By continuing to use carriers, we are not devastating our gene pool. We simply use them in such a way as to avoid producing blind dogs.

In the end, regardless of what the data shows, we have taken a step toward answers to the questions we have today ... hopefully.

Guest · Aug 23, 2008

Jim Drager said:
I also know of 2 other GR's who have not been tested, who were bred to Mav, produced clinically affected dogs, and are "blind". Obviously, I will not disclose who they are...that is up to the owners.

Thanks for some concrete information. I don't know why it is so difficult to get anyone to share this kind of stuff. But we still don't know if the dams of the dogs you mention are Carriers (or Affected) or if the clinically affected dogs have the prcd form of PRA, correct?

Ps...are you coming to the Specialty so that you may join the legions of us seeking to feel "cheap in the morning" :>)

Hey, what happened to cheap and dirty? If I make it out there, I want to get my money's worth!

Eric Johnson said:
There are a whole range of possibilities.

1. Goldens have something about their make-up that causes the problems to be later onset or expressed differently.

This is what I would like to find out.

It's tough (and expensive) to be the leader.

No kidding.

Melanie

Eric Johnson · Aug 23, 2008

Unless they have changed their policy. Optigen runs as a closed registry. They will only reveal the dogs that are clear. Frankly I think they are wrong but their position is that they are a testing service, not a registry with all the potential legal implications.

In our case (Tollers), the tradition of posting the results, all of them or essentially all of them, came into being before the club got the first copy of the registry from Optigen. People routinely post them to Toller-L which has almost 1,000 members and is worldwide. Now the results are also posted on TollerData and I don't think anyone really refers to the Optigen report except for verification. As long as that's been in place, I have never had a request to change the PRA result. Same is true with Collie Eye Anamoly.

Eric

Bud Bass · Aug 23, 2008

We had a golden i purchased for my wife in 98, when he was about 3 we noticed problems with him seeing, then we had a vet who specialized in eys in Anchoarge and he diagnosed our dog with PRA, we were told is that is is a fairly common eye problem with goldens. No test was performed at the time, just a visual examination, over the next few years our golden slowly lost his sight. When he died this past winter, he could see shadows, follow light, but i am sure no details. This thread is really the first real information I've had on the desease. Thank you, bud

Gerry Clinchy · Aug 23, 2008

akblackdawg said:
We had a golden i purchased for my wife in 98, when he was about 3 we noticed problems with him seeing, then we had a vet who specialized in eys in Anchoarge and he diagnosed our dog with PRA, we were told is that is is a fairly common eye problem with goldens. No test was performed at the time, just a visual examination, over the next few years our golden slowly lost his sight. When he died this past winter, he could see shadows, follow light, but i am sure no details. This thread is really the first real information I've had on the desease. Thank you, bud

Akblackdog, this is really interesting. I wonder if this vet has more info on why he feels PRA is common in Goldens?

Guest · Aug 23, 2008

Melanie Foster said:
Where do you get the "most likely prcd-PRA" assumption? Without a DNA or clinical diagnosis, it could have been another form of PRA.

Creek Retrievers said:
That is not an assumption, it was diagnosed by a veterinary opthamologist.

The plot thickens:

SteveLowe said:
1. Can an exam by an ACVO determine if PRA is of the prcd variety?

Gerry said:
No. In humans, retinitis pigmentosa is analogous to PRA in dogs. In humans, there are 46 genetic causes of retinitis pigmentosa, encompassing 5 different genetic mechanisms ... for the same clinical symptoms.

This is similar to the situation with PRA in dogs.

No wonder this is so confusing.

Can an opthalmologist diagnose prcd-PRA or not?

Gerry Clinchy · Aug 23, 2008

Melanie Foster said:
The plot thickens:

No wonder this is so confusing. Can an opthalmologist diagnosis prcd-PRA or not?

When Dr. Aguirre dx'd the first GR to test affected he said he had a "gut feeling". Probably very few ACVOs that have seen as much or more PRA than he has ... and he couldn't tell which kind from physical exam alone.

Perhpas Creek Retrievers believes is was "likely prcd-PRA" because of subsequent test results on related descendants?

And, yes, we do have to be careful how we toss around "PRA" without specifying "prcd" or some other form.

If I have an affected dog with prcd-PRA today, and I know that a grandparent had PRA (but not DNA tested), it's not unreasonable to at least suspect that the grandparent had the same form of PRA.

If this statement from Optigen is reliable: prcd-PRA is the most common type of PRA and is found in over 20 breeds of dog. Then that would be another reason to suspect it was prcd; though not as specific as the first reason.

I did ask Aguirre if more than one PRA mutation could be present in the same dog. The reply was "Possible, but unlikely." He did not elaborate, so I don't really know the full details on "why".

Guest · Aug 23, 2008

Hi to All commenting on the prcd-pra.

I happen to own the affected 7 1/2 year old dog folks are talking about. You can refer to her by name and it is Daphne.

She fits all the patterns described in the research on the prcd-pra. Both parents carriers - she appears to be the only affected dog in the litter (I think one hasn't been tested ) - the others are carriers and one is clear.

She was diagnosed first by an eye exam. Dr Aguirree encouraged me to send her blood in but was clear to tell me that goldens before with the eye dx had not tested prcd-pra. She showed no visible signs to me of sight loss at that time. Today - she has clear problems at night and is beginning to have other limited vision - ie doesn't see the bumper going over her head - waits for it to land to locate it. Perhaps it will still be a long time before she loses her sight totally - I sure hope so.

Daphne had been bred before the diagnosis came. All her puppies tested as carriers ( I paid to test them once all this happened as the sire of the litter had died prior to the diagnosis and there was nothing collected on him. Felt I owed the owners of the puppies that as I wouldn't have bred her if I had any idea this was going on and the only way I would know if I bred to a clear dog or not would be by the results of testing the litter). The bitch I kept from that litter was later bred to a clear dog and she produced 5 carriers and 3 clear in her litter - like the research suggests she would. While more research needs to be done - guess I am willing to spend the money with Optigen so we might be able to avoid this in the future. Would be easier and cheaper to ignore this and some are clearly doing that.

If you would like more info on Daphne and her affected issues - feel free to write me directly.

Mardi

Guest · Aug 23, 2008

Gerry Clinchy said:
Perhaps Creek Retrievers believes is was "likely prcd-PRA" because of subsequent test results on related descendants?

Becky specifically said "That is not an assumption, it was diagnosed by a veterinary opthamologist."

Which information can be confirmed?

And this is worth repeating:

Melanie Foster said:
From the Optigen site:

"Conditions that seem to be prcd-PRA might instead be another disease and might not be inherited."

How is anyone supposed to know what to believe?

ps Randy, hope we didn't miss too many of your no birds today. Had to skip the Derby this weekend.

afdahl · Aug 23, 2008

I haven't seen anyone mention an electroretinogram. My understanding is that it can give a definitive diagnosis for prcd-PRA. In a breed with a typical age of onset of 5-7 years, according to my (former) veterinary ophthalmologist, the electroretinogram will show characteristic changes by 18 months.

This information dates back to when Dr. Aguirre was developing the marker tests and different breeds were being treated separately. I haven't considered doing an erg since the Optigen tests came out.

Amy Dahl

Guest · Aug 24, 2008

Gerry:

If there are 5 or 6 carrierXcarrier breedings, there may only be 5 or 6 affected.

These are just a few of the breedings I know of off the top of my head in the last couple of years that could potentially create affected dogs:

http://www.k9data.com/pedigree.asp?ID=222355

http://www.k9data.com/pedigree.asp?ID=303569

http://www.k9data.com/pedigree.asp?ID=295280

http://www.k9data.com/pedigree.asp?ID=261540

http://www.k9data.com/pedigree.asp?ID=281084

http://www.k9data.com/pedigree.asp?ID=280290

http://www.k9data.com/pedigree.asp?ID=302912

Since these breedings have been done recently (before the prcd-PRA test was available), why hasn't the breeding of their ancestors produced more blind dogs?

Melanie

Creek Retrievers · Aug 24, 2008

Melanie Foster said:
Becky specifically said "That is not an assumption, it was diagnosed by a veterinary opthamologist."

Which information can be confirmed?

And this is worth repeating:

How is anyone supposed to know what to believe?

ps Randy, hope we didn't miss too many of your no birds today. Had to skip the Derby this weekend.

It very well could have been another form of PRA and until offspring are tested the world may never know.

Melanie as for this,

"Conditions that seem to be prcd-PRA might instead be another disease and might not be inherited."

Why do you think they offer DNA testing now for prcd-PRA? It helps rule out prcd-PRA. I am not sure what type of silver lining your looking for? You can refute that dogs who might have had PRA in the past might not have had prcd PRA, but it is hard to deny the disease exists. If a dog does come back affected, should we sit and question if they will go blind or how diminished their eye sight will be? It will probably vary from dog to dog.

For the possible test breedings, unless all the pups are tested, it is hard to tell how many will come back affected.

Here are some questions...

Do you think pups that end up in pet homes will be tested? Do you think that this makes the percentage for carriers or affected dogs lower or higher?

I don't think we are getting an accurate picture of the prcd-PRA for the Golden Retriever population since the sample size is pretty small compared to the overall population.

With selective breeding how many generations would it take to eliminate prcd-PRA carriers? My unscientific calculation would be several generations or even one generation if you only breed the clear pups from a carrier to clear breeding. Maybe I missed something here, I did not take a genetics class in college.

Guest · Aug 24, 2008

Melanie Foster said:
Gerry:

If there are 5 or 6 carrierXcarrier breedings, there may only be 5 or 6 affected.

These are just a few of the breedings I know of off the top of my head in the last couple of years that could potentially create affected dogs:

http://www.k9data.com/pedigree.asp?ID=222355

http://www.k9data.com/pedigree.asp?ID=303569

http://www.k9data.com/pedigree.asp?ID=295280

http://www.k9data.com/pedigree.asp?ID=261540

http://www.k9data.com/pedigree.asp?ID=281084

http://www.k9data.com/pedigree.asp?ID=280290

http://www.k9data.com/pedigree.asp?ID=302912

Since these breedings have been done recently (before the prcd-PRA test was available), why hasn't the breeding of their ancestors produced more blind dogs?

Melanie

Are these all carrier to carrier breedings? Without looking up each dog - not sure we could predict affected without knowing we had carrier to carrier or affected to carrier. I recognize a couple of the dogs as carriers. If they are carrier to carrier, there will be at least a few affected. Hopefully - those dogs from carrier to carrier breedings will all be tested. A tough thing to accomplish as the test is expensive and some folks just won't do it.

Gerry Clinchy · Aug 24, 2008

Melanie Foster said:
Becky specifically said "That is not an assumption, it was diagnosed by a veterinary opthamologist."

Which information can be confirmed?

And this is worth repeating:

How is anyone supposed to know what to believe?

The entire quote helps a bit:
"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 "

I think this does say that there aren't always easy answers in the gathering of data.

As Amy mentioned, in some cases, electroretinograph will be used to help dx PRA. It somehow measures the signals sent from the eye to the brain.

One case that occurred last year: Owner noticed dog having vision problems. No physical evidence of PRA at first ACVO. Second ACVO not so sure about that. ERG done & does not reveal results consistent with PRA. Optigen test indicates clear for prcd-PRA. Dog finally goes to Dr. Aguirre. Another ERG is done.Second ERG also does not indicate PRA either. Final dx: Dog has a vision problem related to depth perception, but not PRA.

Evidently, the ERG can detect something that might indicate PRA even before a regular physical exam does (as Amy says). Before DNA testing was available, the Poodles used the ERG quite frequently.Not cheap & I was told that it requires anesthesia. Since Amy has actually done one, she might add enlightenment on that.

I don't think the ACVOs take a dx of PRA lightly. If they have doubts, it appears they explore further to reach what they believe is an accurate dx.

Now if we'd like to fund something ... according to Optigen there are "a few" Goldens who are affected by test but not old enough for physical symptoms. If the owners were willing to do ERGs, might we "fund" the cost of those ERGs? It might allow an 18 to 24-mo. expediting of the info we seek. OTOH, I'm not sure exactly how accurate the ERGs are considered to be. Again, maybe Amy has that info.

Gerry Clinchy · Aug 24, 2008

Melanie Foster said:
These are just a few of the breedings I know of off the top of my head in the last couple of years that could potentially create affected dogs:

http://www.k9data.com/pedigree.asp?ID=222355

http://www.k9data.com/pedigree.asp?ID=303569

http://www.k9data.com/pedigree.asp?ID=295280

http://www.k9data.com/pedigree.asp?ID=261540

http://www.k9data.com/pedigree.asp?ID=281084

http://www.k9data.com/pedigree.asp?ID=280290

http://www.k9data.com/pedigree.asp?ID=302912

Since these breedings have been done recently (before the prcd-PRA test was available), why hasn't the breeding of their ancestors produced more blind dogs?

Melanie

In all of these cases at least one clear ancestor appears in the gr-parent generation. In every case there is missing information on one of the gr-parents on the other side.

So, if each side had one clear gr-parent was available to "neutralize" the mutation, no affected offspring would result.

Unfortunately, some of those gr-parents may no longer be available for testing to gather information backward.

We always get back to the need for more data from the dogs that are here now & available for testing.

This may also be a good time to again express thanks to those owners who gave us the information we do have. Frozen semen testing has given us some of the clues that allow us to try and piece the puzzle together.

prcd-PRA Testing Goldens--a bunch of smoke?

Jim Drager

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Eric Johnson

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