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The CEA affected rate in North America is about 2.5% with a 25% carrier rate. The impact of this genetic disease is significantly higher than that of TNS.

So what is the impact? From what I've read, in 75-90% of homozygous dogs, there will be no identifiable visual impairment. Anyone here had a blind puppy?

 

very few dogs were imported into the USA (until AKC recognition) from a gene pool with a 10% carrier rate.

That's an assumption, Mark. You don't know that the UK doesn't have a 10% carrier rate. After all, we're supposed to have up to 30% TNS carriers in my small neck of the woods and no-one but me has ever had an affected litter. And all of our dogs derive from populations that apparently have a 25% CEA carrier rate, and we have no CEA problem (except that 2/7 of my dogs are carriers...).

 

If there is a very low rate of this disease in your country or in your family lines does it make sense to go have this test performed or for your government to force everyone to have the test just to measure the carrier rates?

Putting aside the obvious issues differentiating dog vs. human breeding and the roles of government health services vs. breed registries, our government do actually fund programs for prenatal and postnatal screening for diseases, some of which have relatively low rates. There is continuing talk of offering widespread pre-conception testing for diseases like CF, even to people with no family history (as is the way with recessive genes, most people who carry CF have no family history of it). But of course, before our government implements any sort of screening program, study is done into what the rates are in our population.

 

And then it all comes down to what cost-benefit analysis, doesn't it? And for working dog populations, I imagine that could include not only the welfare of individual dog or breeder, but also using genetic screening for the good of the breed as a whole, preventing any newly arising health issues from interfering with the more important breeding considerations.

 

Or not. Either way, as long as it works for those involved.

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You are correct; I don't know the carrier rate of TNS in the UK. My comment was about importation from a gene pool with a measured carrier rate.

 

It is highly likely that the carrier rate in a subordinate gene pool will be different than the parent gene pool due to the genetic bottle neck of importation of dogs. This genetic bottle neck could easily create a different CEA rate and TNS rate just like a popular sire affect; it will all come down to the rate of these genetic mutations in the imported dogs.

 

Using the experiences one or two breeders/dog owners is hardly representative of the entire gene pool. The other difficulty is that when the testing rate is low or from voluntary testing, the statistics will likely be biased away from the true population statistics.

 

This last item is very important to keep in mind when reading the results of research in terms of how the samples were collected; the samples were not a random samples of the gene pool they were submitted from owners with an awareness (or personal interest) of the disease being studied.

 

 

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So what is the impact? From what I've read, in 75-90% of homozygous dogs, there will be no identifiable visual impairment. Anyone here had a blind puppy?

There are two impacts. The one you're interested in is the manifestation of the disease in that individual dog. This can range from "go normal" (no impact on vision) to blindness. The one I'm more interested in is the impact on the gene pool. "Go normals" will have no visible impact on vision; however, if bred this dog will lead to an increase in the rate of this mutation in the gene pool every time it is bred.

 

 

 

Clear X Affected = 100% Carriers

Carrier X Affected = on average, 50% Affected, 50% Carriers

Affected X Affected = 100% Affected

 

 

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Happily, this will be my last post on this subject. It's taking too much time, and as a freelancer, time really is money, so I can't really devote any more time than I already have to this.

 

Well, some of the state working dog groups are now encouraging and facilitating testing. And people with Australian working-bred dogs relatively unrelated to our affected litter (ie no recent common ancestors) have come up as carriers. In the absence of a widespread comprehensive population testing program, that's a good indicator that it is more widespread than people here imagine. And then there's the fact that in the apparently very few ISDS dogs tested, at least a couple have come back as carriers.

 

I don't think any scientist would look at a handful of affected animals and make the extrapolation that the problem must be far more widespread in the general population. If you think of the total number of dogs reported to be TNS carriers compared to the total number of dogs of that breed, the number likely isn't statistically significant. Combine that with the fact that the mutation is FATAL and it just doesn't make sense to assume that there's a large percentage of carriers in the population. If there were a large percentage, there would be "accidental" crossings of carrier to carrier, and people would be losing litters. As Eileen pointed out, people pay attention to litters here in the US. I guess it's possible that some millers are losing whole litters that no one is hearing about, but I also imagine if you're raising dogs as a business, you might try to figure out why you're losing litters as those losses cut into profit. CEA, adult onset deafness, epilepsy, etc., can't really be compared because those diseases generally aren't fatal (with the exception of epilepsy, but even then, young dogs generally don't have their first seizures until around age 2, so they certainly make it through puppyhood). I guess what I don't understand is why you think, in the absence of losses of large numbers of puppies from a fatal disease like TNS, that TNS is much more widespread in the general population. I understand that your dogs carried it and several related (though not closely) dogs carried it, plus some dogs from one farm in the UK, plus TWO dogs that are apparently strictly ISDS bred. Although it has affected you greatly as a breeder, there's no getting around the fact that people aren't losing puppies right and left, and if the carrier percentage was high enough, people would unknowingly be breeding carriers together and producing affected (dying) puppies. That doesn't seem to be the case, unless there's some huge conspiracy to hide puppy deaths in the working dog community (which obviously I do not believe).

 

Please don't put words into my mouth- I'm not advocating wholesale testing in ABCA and ISDS dogs, just as I'm not advocating wholesale testing in Australian dogs.

I'm not putting words in your mouth. You've asked several times why ABCA or ISDS isn't testing working dogs for presence of the TNS gene. How else does one interpret that question? Either you would like to see as many dogs as possible tested or you don't care. The impression I get is that you think more dogs should be tested so the true carrier rate can be determined. If that's not what you've been saying in all these many posts, then I apologize for misinterpreting, but then again if it's not what you're saying, why are we still discussing a widespread need to test, when most of us here in the US have noted that it doesn't appear to be a problem here?

 

But neither TNS or CEA are "on the radar" for almost all Australian working dog breeders, yet quite a high proportion of dogs tested are carriers. So it doesn't seem like "on the radar" is necessarily such a good test of existence of these genes.

 

But in this case you are misapplying the results of limited testing to the general population at large. The dogs tested were suspected of having the mutation, so it shoudn't be a surprise to find that they are carriers. This is the whole "results skewed by the population tested" scenario. To go back to my Amish scenario I posted earlier: If a disease (like Cohen's) is recognized in a population and then subsequent testing is performed on other members of that same population (including their somewhat distant relatives) and a high rate of incidence is observed in the tested population, that would be an expected result based on population genetics. But no scientist is going to conjecture that because the disease exists at a high rate in the tested population (the population who exhibited signs/sypmptoms in the first place) means that the rate of mutation is similarly high in the general population of Caucasion humans of Germanic descent. But that's the argument you seem to be making here for others to test for TNS.

 

I do just think it's weird that so many breeders are happy to be forced to routinely test for CEA when it sounds like it isn't a problem or even "on the radar" for most of them, yet the idea of even random population sampling for TNS is not a popular idea.

This has already been addressed by others.

 

J.

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Please don't put words into my mouth- I'm not advocating wholesale testing in ABCA and ISDS dogs, just as I'm not advocating wholesale testing in Australian dogs.

 

So let me ask you this, then. What is it that you are advocating that you would like U.S. working breeders to pull from this conversation?

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Pearse suggested that it should be Alan Wilton's responsibility, and yes, if he was trying to get research funding for TNS testing from those groups, sure. But the test has already been developed. The information on TNS prevalence in various populations is surely of most interest to those populations, not a busy researcher with no direct financial interest in pushing the test and a full plate of other projects. Do we know that the ISDS haven't discussed it with the researchers, anyway?

 

Actually I didn't suggest that at all. What I suggested is that if Dr. Wilton has information to suggest that this is a problem that the ISDS and ABCA ought to be aware of, it would be good of him to let the ISDS and ABCA know. Both organizations are more likely to pay attention to a warning coming from the only scientist in the field capable of testing for the disease, and the only person on the planet with actual incidence data, than they are from a few anecdotal reports on Internet chat sites.

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Using the experiences one or two breeders/dog owners is hardly representative of the entire gene pool. The other difficulty is that when the testing rate is low or from voluntary testing, the statistics will likely be biased away from the true population statistics.

Sure. So when the testing rate is as low as it is for TNS in ISDS/ABCA dogs (or CEA in Australian border collies), we really have almost no useful information about the percentage of carriers in the population.

 

It's fair enough to assume that the gene probably doesn't exist in this population, and has likely developed as a mutation early in a related (but different) population.

 

If we then find out that someone, with no real justification (no "at risk" dogs), has tested a few dogs from our "low risk" population and found carriers, it would be unreasonable to keep assuming that it doesn't exist in this population. Without further testing to establish the rate in this population, it isn't possible to say any more about it. Especially where the disease expression may be variable enough to make "affected" cases hard to identify.

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Actually I didn't suggest that at all. What I suggested is that if Dr. Wilton has information to suggest that this is a problem that the ISDS and ABCA ought to be aware of, it would be good of him to let the ISDS and ABCA know. Both organizations are more likely to pay attention to a warning coming from the only scientist in the field capable of testing for the disease, and the only person on the planet with actual incidence data, than they are from a few anecdotal reports on Internet chat sites.

Okay. But I'm not Alan Wilton, so if you think he's not doing his bit, or that he's irresponsible to publish the statements he has about TNS occuring in the ISDS/UK population, you'd get more results by contacting him (I think his details are readily available via Google, or the Univesity of NSW) than by putting it out there on an internet chat forum.

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I don't think any scientist would look at a handful of affected animals and make the extrapolation that the problem must be far more widespread in the general population.

No, but if a small number of animals in a population so far presumed to be entirely free of the disease are tested and some of them found to be carriers, then they could hypothesise that the gene may be more prevalent.

 

Combine that with the fact that the mutation is FATAL and it just doesn't make sense to assume that there's a large percentage of carriers in the population. If there were a large percentage, there would be "accidental" crossings of carrier to carrier, and people would be losing litters.

And this comes back to the fact that my local dog population supposedly has a 30% carrier rate, and yet no other affected litters have been identified (and yes, we pay attention to litters here too). Which for me, suggests that it may present in ways that are not the classical picture, maybe a stillborn pup or even reabsorbed pups.

 

I guess what I don't understand is why you think, in the absence of losses of large numbers of puppies from a fatal disease like TNS, that TNS is much more widespread in the general population.

I don't think it is more widespread, I just think it is possible that it is. That would be because of what I've written above.

 

I understand that your dogs carried it and several related (though not closely) dogs carried it, plus some dogs from one farm in the UK, plus TWO dogs that are apparently strictly ISDS bred.

The dogs I've mentioned interstate aren't particularly related to my carriers, at least anymore related than Henniker Spyro or Wintertime Coast would be to a reasonable number of US dogs.

 

You've asked several times why ABCA or ISDS isn't testing working dogs for presence of the TNS gene...The impression I get is that you think more dogs should be tested so the true carrier rate can be determined.

No, I've said I think that if the ISDS or ABCA (or their members) want to determine the carrier rate, they should do more testing. I couldn't actually care less (except as a matter of intellectual interest) whether they do.

 

I do care that people continue to make statements like "it doesn't exist in working dogs", when there is no evidence to support this, and the little evidence there is contradicts it.

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So let me ask you this, then. What is it that you are advocating that you would like U.S. working breeders to pull from this conversation?

I'm not advocating anything. I wanted to clarify some comments in the first couple of pages regarding TNS, because I think they are incorrect, and I wanted to get some viewpoints and information relating to how and why ABCA and individual breeders handle a disease like CEA, which despite not existing on any radars over here, is now being found in randomly tested dogs. Also about how testing for inherited diseases is/should be handled in general, particularly "new" diseases that may appear, not just on an individual level, but for population health reasons.

 

The points regarding TNS I've made are:

a) it doesn't just exist in show dogs. It exists (at unknown rates) in Australian working dogs as well as ISDS dogs with no Aus/NZ breeding.

b ) It is apparently possible for a working dog population have a high rate of carriers but no identified TNS affected litters.

c) therefore I don't feel we can assume an inconsequential carrier rate in any particular population just because there are no anecdotal reports of classically affected pups coming to public attention.

 

Please note: I'm not telling anyone in the US or UK or Australia to test or not, for TNS or CEA or even with relatively blunt tools like hip scoring. I guess I do think that TNS should be a teeny weeny bit "on the radar" of working border collie people and organisations worldwide, although this does not mean they should be routinely or even experimentally testing for it at this stage.

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For folks who might be interested in this issue, these are a few more dogs with no Oz/NZ show lines that have tested as TNS carriers (none located in the USA). Thanks to the owners of these dogs for reporting test results. Someone mentioned earlier that Alan Wilton worked for a University and does not profit from TNS testing - this is correct. He is a scientist devoted to research and has done some wonderful work - hopefully more to come on some other issues.

Sonja

 

Amazing Troya From Stone Gardens NHSB.2569575

Croxlea Catalina KC-AE01974205

Gail Fan E'Rispinge NHSB.G1-2394022

Henniker Spyro ISDS.259652

Highfield Hazza Chance ISDS.256923

Highyews Jaro At Tagnyre KC-AE0901654 ISDS.27164

Locheil Chasing Rainbows SB#.2805CG

Red Spotted Loneliness Of In And Out ZBrH.7838

Thunder Storm Over Tosari [uK] KC-Y5038501Z01

Wintertime Coast ISDS.306261 / KC-AL0901346

Boylee Barney WA.AA1152

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For folks who might be interested in this issue, these are a few more dogs with no Oz/NZ show lines that have tested as TNS carriers (none located in the USA). Thanks to the owners of these dogs for reporting test results. Someone mentioned earlier that Alan Wilton worked for a University and does not profit from TNS testing - this is correct. He is a scientist devoted to research and has done some wonderful work - hopefully more to come on some other issues.

Sonja

 

Amazing Troya From Stone Gardens NHSB.2569575

Croxlea Catalina KC-AE01974205

Gail Fan E'Rispinge NHSB.G1-2394022

Henniker Spyro ISDS.259652

Highfield Hazza Chance ISDS.256923

Highyews Jaro At Tagnyre KC-AE0901654 ISDS.27164

Locheil Chasing Rainbows SB#.2805CG

Red Spotted Loneliness Of In And Out ZBrH.7838

Thunder Storm Over Tosari [uK] KC-Y5038501Z01

Wintertime Coast ISDS.306261 / KC-AL0901346

Boylee Barney WA.AA1152

 

 

 

Being only used to names of working border collies which are usually one word names, not including a ( sometimes ) kennel name, these names listed sound like they are show dogs. I may be wrong but the ISDS does not appear to have the same disapproval of KC dogs getting ISDS papers as does the ABC of USA dogs getting AKC papers. In my Sheepdog News magazine ( offical magazine of the ISDS) which I receive, there has been discussion of the "double reg" dogs within the ISDS. It seems to be more of a live and let live, as the official who was quoted did not seem worried that the working border collies were in much danger of the show collies "

taking over" and/or being any influence on the working dog.I guess where I am going with this --is possibly the ISDS reg dogs had KC papers first, thus the only fancy names, versus them being working ISDS dogs who joined the KC reg later. Just a thought. I know that of the three of my registered Border collies have no ancestors with any names even remotely as fancy or long as these dogs listed here. Of my dogs, one was born in Wales, one's dam was born in Wales, and one's sire was born in Wales. They are all reg with ABCA and ISDS. I have the extended pedigree on all three . Other than an occasional keenel name, all the dogs are one work names, just as the ISDS suggest when you do when you register your pups.

 

I don't know if there is anything to my observation, but I have studied ISDS pedigrees on many dogs other than my own, and just have not run across this type of longish names before. I think if I were doing any research on what "type" of Border Collie is or is not affected by any disease I would want an extended pedigree before labeling them .

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How many of these above dogs go back to the Blue or whatever the dogs name was who was registered on a merit through ISDS without a known pedigree?

 

Can you post your carrier dog's pedigrees? And the "farm" dogs from the UK? And maybe a few example pedigrees of the other working dogs being tested and prove as carriers thatyou know of?

 

We test for CEA because blind dogs are useless as sheepdogs. And yes, I've seen dogs/heard of dogs affect by it. I've also seen/heard of dogs with epilepsy and deafness in young dogs. TNS and CL? Never.

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Being only used to names of working border collies which are usually one word names, not including a ( sometimes ) kennel name, these names listed sound like they are show dogs.

I don't know about most on that list, but Henniker Spyro, Wintertime Coast and Boylee Barney are not from show-bred dogs. In Australia, our trialling and working dog registration system usually has prefixes. So most of our registered dogs will carry a prefix. The rules differ from state to state, but in my state the dog's name must be one word, plus a prefix if the breeder has one. Boylee Barney is a relative of one of my carrier dogs and he isn't a show dog. His owner has a website here.

 

I may be wrong but the ISDS does not appear to have the same disapproval of KC dogs getting ISDS papers as does the ABC of USA dogs getting AKC papers. In my Sheepdog News magazine ( offical magazine of the ISDS) which I receive, there has been discussion of the "double reg" dogs within the ISDS...

is possibly the ISDS reg dogs had KC papers first, thus the only fancy names, versus them being working ISDS dogs who joined the KC reg later. Just a thought.

You're a bit wrong. Some people within the ISDS may have less disapproval of dual registration, but they don't just hand out ISDS registration willy nilly. To be ISDS registered as an adult, dogs still have to undergo ROM testing, which is based on a test much like the ABCA one, or I think they can get ROM'ed on trial results.

 

The reason there are "double reg" dogs within the ISDS is the same one that explains "double reg" dogs in the ABCA- the Kennel Club accepts ISDS registered dogs onto its stud books, not the other way around.

 

I don't think there has been more than one show-bred dog that has ever been ROM'ed with the ISDS, and possibly not even that. I'm sure someone knows.

 

Other than an occasional keenel name, all the dogs are one work names, just as the ISDS suggest when you do when you register your pups.

The ISDS certainly allow registration and use of prefixes. Wiston Cap? Bwlch Taff? Dewi Tweed? And in the UK, quite a lot of the obedience and agility people source their dogs from working breeders. As I understand it, they have the choice then to register the dog under an entirely different name with the KC, so many do. It doesn't mean the dogs are show-bred, you need to check out their pedigrees to determine that. Many of them have a single word ISDS name as well. I think some of pucksfurcoat's list are dogs from European countries where the same thing applies.

 

At a guess, people from sports backgrounds are much more likely to be doing TNS testing, so it shouldn't be surprising that most of the results are from those sources.

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How many of these above dogs go back to the Blue or whatever the dogs name was who was registered on a merit through ISDS without a known pedigree?

I haven't been through that recent list, Katelynn, but I've gone back on Henniker Spyro and Wintertime Coast, and neither of them has Blue (or any "well bred Field Spaniels" :lol: ). There are a couple of unregistered dogs listed, from the 50s, 60s and some in the early 70s, but no suggestion at all that they were show dogs.

 

Can you post your carrier dog's pedigrees? And the "farm" dogs from the UK? And maybe a few example pedigrees of the other working dogs being tested and prove as carriers thatyou know of?

As we established in the previous TNS discussion, I can certainly post their pedigrees (and I will do so when I get home tonight, if you'd like to see them), but it won't do you much good, because you won't know any of the dogs listed, and unless you have the Australian state studbooks, you won't be able to do much with it. No show dogs listed, though.

 

And if you're asking me to provide the other pedigrees, then unfortunately I don't have access to the Uni of NSW information. When you send samples for testing, you have to agree to publication of the results, and if people haven't agreed to this, then they can't really go releasing them. pucksfurcoat has provided some just now though, so that should be worth looking into. Why not start with Henniker Spyro and Wintertime Coast?

 

We test for CEA because blind dogs are useless as sheepdogs. And yes, I've seen dogs/heard of dogs affect by it.

Could you tell us a bit about those dogs please?

And what is your take on testing issues generally? Should people only be testing for diseases with which they have personal or close experience? How prevalent does a disease or a gene need to be before breeders should test for it? And do you agree with PPs that advertising of health testing is often a red flag for a breeder's motives?

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b ) It is apparently possible for a working dog population have a high rate of carriers but no identified TNS affected litters.

It is mathmatically possible to have a high (lets say >10%) carrier rate and not know it IF there are very few carrier X carrier breedings or these breedings do not produce pups that can be identified as being affected with TNS.

 

What is the likelihood that a carrier X carrier breeding would produce affected pups that were not identified as having TNS? Is there such a thing as a "go normal" with TNS affected dogs?

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Highfield Hazza Chance ISDS.256923

 

I know this dog and his owner. An agility not working dog and I assume the reason for testing was that someone wanted to use him for stud for a sport breeding. Highfield isn't a breeding kennel name, just one used by the family for their agility dogs.

 

Sire and Dam

ROY (ISDS 215097) TAMMY (ISDS 243153)

 

Highyews Jaro At Tagnyre KC-AE0901654 ISDS.27164

 

Highyews are local to where I live. Working/sport/S&R dogs. I know several people with them and would be more concerned about HD than anything else if pigs were to fly by the window and I wanted to buy a pup.

 

Locheil Chasing Rainbows SB#.2805CG

 

Locheil dogs are primarily show dogs with some sport. We have an impossibly hairy half Locheil dog in the club and I'm told the over abundance of coat comes from that side of the pedigree. (We have a full Locheil on the waiting list and I'm told that is very hairy too.)

 

Looking at the Locheil photo gallery I'd be amazed if they were free of Oz/NZ influence although don't know about the dog in question.

 

Pam

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We test for CEA because blind dogs are useless as sheepdogs. And yes, I've seen dogs/heard of dogs affect by it.

 

I've just taken a call from someone with a 5 year old dog that has CEA and lens luxation and, as she said, all because the breeder didn't test for it. Her dog is virtually blind.

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Absolutely.

Although, as I understand it, the ISDS take on this was that by recognising the frequency of a disease gene in the population and watching for it (ie eye testing) and trying to control breeding to some extent or at least compel awareness of it, they could limit the prevalence of the gene in the population before it became such a problem that it interfered with breeding for more important things (ie working ability).

 

Yes, but bear in mind that ISDS adopted the eye exam policy back before there was a DNA test for CEA. I think it's reasonable to be more scared about genes for a disease silently infiltrating your population if there isn't a test to turn to as deemed necessary.

 

So it seems like it's a balancing act between raising awareness and informed breeding to prevent the disease from becoming so prevalent in the population that it affects breeding practices, and overdoing it to the extent that the testing itself limits breeding practices.

 

I'd agree with that.

 

So by that definition, we shouldn't be testing for CEA over here then, and I guess most people shouldn't really be testing for TNS either. I think this is probably the way it will continue to be, although on a personal level I guess we will continue to test the occasional dog for one or the other.

 

If I were in your position, I would probably test all dogs I was breeding for both. But I wouldn't be advertising the favorable test results on my website. ;)

 

I wonder if you think there is a point at which breeders with the ABCA should stop testing for CEA? Is the ABCA monitoring CEA rates and considering when testing should no longer be recommended? I noticed that the eye testing at the Nationals (I think?) is no longer required- is that part of this process (presumably for PRA or whatever rather than CEA, but same issue)?

 

No, I doubt we will reach a point at which breeders with the ABCA should stop testing for CEA. In fact, the carrier rate tends to go up a bit when there is a test available, since people can breed carriers (or even affecteds) to tested normals without fear of producing affected pups, and those breedings are likely to produce some carriers. The last time I looked at OptiGen reports that seemed to be the case, although the data are skewed now by the fact that so many normal dogs are clear by parentage and therefore not being tested. Some breeders apply a more rigorous standard for breeding a dog who's a carrier (i.e., the dog has to be better to merit breeding), but others are content just to avoid producing affected offspring. The eye exams for the finals were discontinued, basically, because the doc was seeing virtually no CEA now, and no PRA. But DNA testing for carriers is how we got there, and it still makes sense.

 

Eg. hip dysplasia- the general attitude in Australia is that unsound dogs will show up in their work, and since hip xraying is difficult logistically as well as financially, and there's debate about its usefulness in these circumstances, no-one does it. I actually think that's a fair call, but others here on these Boards would probably disagree. And then I do find myself worrying that if we continue to wait for something like CEA to actually become a declared problem, given that it could already be be present at the same rates here as elsewhere, it may rear up and bite us later on.

 

Well, hip dysplasia is a whole different can of worms, since we don't have a genetic yes/no test for it the way we do for CEA or TNS.

 

So what is the impact? From what I've read, in 75-90% of homozygous dogs, there will be no identifiable visual impairment. Anyone here had a blind puppy?

 

I have not had a blind puppy, but back before the CEA test existed I bred a litter that produced some pups with CEA. Both parents had clear eye exam results. When I took the pups for their eye exam, the doc said 4 out of the 7 had CEA, although it would not impair their functional vision and would never be noticed. I placed them in pet homes on spay/neuter contracts, and obtained proof of neutering. They lived normal lives and their people all were happy with them, but it's still hard telling potential buyers that this nice little pup you produced has a defect. One of the pups whose exam was normal and who went to a working home was later tested when the DNA test came along, and was found normal, which meant that both parents had been carriers (rather than one of them having been affected and not recognized as such at its eye exam). As you probably know, the severity of the expression of CEA is affected by other gene(s) than the basic CEA gene that we have a test for, so even though the majority of dogs born with CEA may have functionally normal or near-normal vision, there is no way of knowing whether that will be the case or not in any particular breeding that can produce CEA.

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It is mathmatically possible to have a high (lets say >10%) carrier rate and not know it IF there are very few carrier X carrier breedings or these breedings do not produce pups that can be identified as being affected with TNS.

 

What is the likelihood that a carrier X carrier breeding would produce affected pups that were not identified as having TNS? Is there such a thing as a "go normal" with TNS affected dogs?

No, there's no such thing as "go normal", but I think it's possible that there are other presentations of TNS than that usually described (ie not always the sickly ferret-faced puppies).

 

Our local sheepdog population, as sampled so far (a reasonable proportion of dogs) apparently has a 30% rate of carriers. There's a high level of awareness of TNS, and there has always been openness about genetic disease (breeders discuss epilepsy, HD etc). Yet even with a 30% carrier rate, our two affected pups are still the only ones that have been identified here.

 

So I wonder if TNS can also present as an occasional stillbirth, or even just a small litter (with pups reabsorbed).

 

Even in show dogs, it's not as if TNS litters were everywhere (as I understand it). Until the test was developed, TNS was still believed to be isolated to a couple of show dog lines, descended from a couple of dogs. But since the test became available and show breeders everywhere started testing, carriers have apparently been found in all those "unaffected" lines. It doesn't make sense to me that more "classical" TNS litters wouldn't have been identified in these lines earlier, unless there is significant variation in the disease expression.

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Our local sheepdog population, as sampled so far (a reasonable proportion of dogs) apparently has a 30% rate of carriers. There's a high level of awareness of TNS, and there has always been openness about genetic disease (breeders discuss epilepsy, HD etc). Yet even with a 30% carrier rate, our two affected pups are still the only ones that have been identified here.

 

So I wonder if TNS can also present as an occasional stillbirth, or even just a small litter (with pups reabsorbed).

 

In your local sheepdog population, are you seeing stillbirths (without other obvious explanations like uterine inertia), or small litters?

 

Also, I wonder if you know of any breedings between two dogs that have been identified as carriers (other than your own one)? If so, what resulted from the breedings?

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Assuming the measured 30% carrier rate accurately reflects the rate in the gene pool, with a simple recessive genetic defect you should be finding "affected" dogs with the genetic testing; unless most affected dogs die.

 

 

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I looked up some pedigree info on some of the dogs. While I'm not finding that these dogs go back to any NZ/Aust. show lines, most of them come from long lines of show champions and it's a long way back behind the dogs before you hit any ISDS registered dogs. I don't know enough about this to draw any conclusions from it, but it reminds me of when I'm having a conversation with someone with show dogs, and they talk about how their dogs are from "working lines" ... yeah ... if you go back about 25 generations.

 

Gail Fan E'Rispinge

Highyews Jaro At Tagnrye <--- Can't find his pedigree

Locheil Chasing Rainbows <--- HERE is his sire's pedigree and HERE is a pedigree showing the dam's side.

Red Spotted Loneliness Of In And Out

Thunder Storm Over Tosari

Boylee Barney <--- Simon Leaning's dog. He's out of Dajara Woody. Who is Dajara? The only other place I've seen that prefix (if it is a prefix) is in pedigrees belonging to Tonalee and Wildair Border Collies and such, which both list NZ championships on the Dajara parts of the pedigrees. (This is the only dog in the list that I did find working dogs behind it.)

 

So ... just sharing what I found. There's nothing here that makes me want to run out and get my dogs tested.

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I know this dog and his owner. An agility not working dog and I assume the reason for testing was that someone wanted to use him for stud for a sport breeding. Highfield isn't a breeding kennel name, just one used by the family for their agility dogs.

 

Sire and Dam

ROY (ISDS 215097) TAMMY (ISDS 243153)

The fact that they're owned by people who do agility with them doesn't say anything about their ancestry, or the relevance of it to the current discussion. Some sports people definitely do source dogs from pure working lines, and some respected breeders of working sheepdogs have been heavily involved in sports (eg Roy Goutte). Since almost the only people currently interested in testing for TNS are show/sports people, it makes sense that most of the pure ISDS-bred dogs identified as carriers are owned by those sorts of people.

 

I've just had a quick spin through Highfield Hazza Chance's pedigree, and I think I can add him to Henniker Spyro and Wintertime Coast as dogs without any Australian/NZ show breeding.

 

Some of the dogs on that list I would certainly consider show or sports-bred for numerous generations, but if they don't actually have any ancestors imported from Australia/NZ, they still disprove the hypothesis (which I used to subscribe to until recently) that TNS originated in Australia, as a mutation in one of the early sheepdogs behind both our working lines and what became the Show BC.

 

Going through the list of identified carriers and trying to find flaws in their breeding and the people who bred them or own them isn't really helpful for anyone. Regardless of how pointlessly or frivolously bred a dog may be, if it is a carrier of a genetic disease, it had to inherit it from somewhere (unless the mutation developed in that dog, which isn't the case here). If all those ancestors are 100% UK working bred dogs, then some of them must be carriers. Hence it must exist in the non-Australian/NZ population, no?

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I looked up some pedigree info on some of the dogs. While I'm not finding that these dogs go back to any NZ/Aust. show lines, most of them come from long lines of show champions and it's a long way back behind the dogs before you hit any ISDS registered dogs.

Try:

Henniker Spyro

Wintertime Coast

Highfield Hazza Chance

How many generations of show champions are behind those dogs?

 

Boylee Barney <--- Simon Leaning's dog. He's out of Dajara Woody. Who is Dajara? The only other place I've seen that prefix (if it is a prefix) is in pedigrees belonging to Tonalee and Wildair Border Collies and such, which both list NZ championships on the Dajara parts of the pedigrees. (This is the only dog in the list that I did find working dogs behind it.)

That's a different Dajara. There's a NZ show breeder with the same prefix (although it might be Dajarra?). Dajara Woody was bred by a guy who lives near me, definitely no affiliation with show lines. Woody does actually go back to some unregistered farm dogs, although I think one had a registered mother. As it happens though, Boylee Barney probably inherited the TNS gene from his mother, Boylee Sweetpea. Sweetpea was a half-sister and aunt to my carrier dog (Boylee Bill).

 

While I'm here, Eileen, thanks for your post- it was really worth reading. Cheers.

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