Progressive retinal atrophy - IRISH WOLFHOUND HEALTH GROUP

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Progressive Retinal Atrophy



Download      PRA factsheet

This is one of the breed's success stories as the incidence in the breed is very low and we have not had a case for several years now, due to the vigilance and sharing of information within the breed. It is not only because people have tested for it.

The test that is available only tells you if a dog is affected or not, but cannot identify carrier status, so it cannot prevent you from possibly producing it. If a breeder knows that they have carrier lines in their pedigree then they would be advised to test their stock before breeding at an earlier age as the disease might not have shown up by this stage. However, unless you are aware of the carrier lines, this test would not prevent you possibly breeding with a carrier. As there are new people coming into the breed all the time and also those carrier lines disappearing off the 5 generation pedigree, it would be worthwhile keeping PRA at the forefront of our minds as a reminder to check our pedigrees thoroughly before going ahead.

The Irish Wolfhound Study's database can provide a risk analysis as it knows the carrier dogs, so this would be a more reliable way of helping you to breed with a reduced risk. To obtain a risk analysis email Anne Janis. There is also plenty of information in the public domain in the breed about those carrier lines and plenty of people who can help check out a pedigree. So we consider the emphasis should be on testing if you know there is a risk of carrier lines in your pedigree, to encourage a more in depth look at that aspect of the proposed mating.

For more information about those carrier lines and how to manage them, see below.




Background
In autumn 1991 an article appeared in the "Irish Wolfhound" magazine in the UK. It explained that progressive retinal atrophy had been diagnosed in our breed, and named affected hounds as well as describing the method of inheritance. With hindsight, this was the first time a condition had been so described, and the first time owners and breeders had been so open about an inheritable condition discovered within their stock. The usual behaviour amongst competitors prior to the 1990s would be to deny, to hide, or to blame others. There was still some of that, but the exemplary behaviour of the kennels closest to the problem enabled breeders to co-operate and to breed more "safely". No doubt about it, this will have reduced the numbers of affected hounds and carriers within the international breed population.

Other eye conditions do exist in the breed, although there isn't space to discuss these it is important to know they may put in an appearance. Retinal Dysplasia is one such, and there are others. These must be diagnosed by a canine ophthalmologist and reported to a parent Club in the country of origin to enable these "occasional" occurrences to be monitored. Eye problems aren't common, but like all other conditions need watching and breeding away from wherever possible.

The spectre of early onset blindness for a sight hound, the simple method of inheritance (recessive), the reaction of the dog owning public when a breed as large as ours has this condition, gives PRA unusual prominence.

Known carriers and why these matter
What is a "known carrier"? It is both of the parents of an affected hound, the producers of a hound with PRA. Click here for a list of known carriers.

Close relations have been described as "potential carriers". These are the brothers and sisters of an affected hound, and some of the brothers and sisters and parents of the two "known carriers" who produced them. They may not carry the PRA "genetic fault", but we can't tell. We need a blood test that identifies those normally sighted hounds that carry the hidden genetic potential to produce PRA. I have been told of a case of PRA where a carrier was eight generations back on one side and seven generations behind the other. Some things don't ever fall off the back of the pedigree, much as we may hope they will, although the statistical likelihood does fall and I will return to this aspect later.

Some known carriers listed
The first "known affected" hound appeared in Sweden. The parents of this blind hound were English bred, Chs Witchesbroom Sirius and Edeyrn Flame of Witchesbroom. These are therefore "known carriers". Sirius was by Can Ch Roscruge Richelieu of Witchesbroom ex Witchesbroom Cauldron. Flame was by Ch Witchesbroom Wizard ex Edeyrn Troika. Sirius was line bred to Ch Witchesbroom Wizard; his coefficient of inbreeding was 34.21%. Cauldron is the result of a mother son mating, Magic to Ch Wizard. Wizard was the very influential son of Ch Ederyrn Mogul, who was behind Edeyrn Troika. Somewhere in the background will be the hound or hounds that had the original mutation but we have no way of knowing which one or ones. Remember, only the direct parents of a blind hound are proven carriers, and for good or ill in-breeding will usually increase the likelihood of finding just what is in the genotype.

The next young hound to be diagnosed was by Westmount Willie Fionncosach ex Westmount Corona. Willie was sired by Mochras Valentinian (Witchesbroom Wizard ex M. Gaeltara). Corona was by W. Sirius (q.v) ex Westmount Dixie D'Or.

Another affected hound appeared when Westmount Fargo was bred to Corona's litter sister Carma. Fargo was by Willie Fionncosach ex Dixie D'Or. This was a half brother half sister breeding onto Dixie (Buckhurst and Mountebanks lines) but the weight of evidence was beginning to show that the carrier was the Wizard son Valentinian.

Greystone Cendor of Westmount sired PRA to his aunt Westmount Felicia. Cendor was by Fargo ex Carma, both of which had proved themselves as known carriers by being PRA producers when mated together. Normally sighted hounds like Cendor could breed females, which did not possess the hidden defective PRA gene, and his own carrier status would remain hidden - until he mated another carrier, of course . . .

Fargo also produced PRA to Westmount Xie-Xie, a daughter of Valentinian and Dixie D'Or, and to Westmount Dark Ant (Sirius ex Westmount Kim-Biba). Exported to GB, Xie-Xie's brother Xile sired 14 litters. One bitch produced a single case of PRA to him. Bokra Vienna was out of B. Katastrophe (by Wizard) and her sire Bokra Pagan was a grandson of Richelieu (Sirius' sire) through B. Notary. It was horrible to discover that Xile was a PRA carrier; he had a 50:50 chance of this status. Had this daughter died at birth he would have appeared to have sired no cases of PRA in 14 litters, but half his offspring in turn would have been unknown carriers. On balance it is far better that we knew. It also shows how there were comparatively few carriers for him to breed to in the UK population at that time, or it may have shown up before he was seven and retired from stud.

Jill Sims contacted me when she had a dog diagnosed with PRA. Until this point some had argued that the start of the problem might have been "Something Swedish". Her dog was by Edelmar Mendell (Clonara Akbar ex Edelmar Freya). His parents were both offspring of the bitch Edelmar Micah, who was line bred to Ch Wizard through W. Hemlock and Yelxba Claironcita. Freya's sire was another son of Richelieu, Ch Witchesbroom Sorcerer (Richelieu ex Cauldron). Nothing Swedish here!

Fast forward a few years to two more cases of PRA, again the axe falling from an unknown direction as these littermates came from a breeding that had not been implicated earlier. Tragically the Bokra kennel had their second experience, their alternative bitch line upon which they had concentrated when breeding away from the "Vienna" lines. Ch Bokra Garbo was mated to Ch Seplecur Trojan of Foinaven. The only connection to the earlier PRA cases seemed to be through Garbo's dam, Ch Chater Tapestry of Bokra, a granddaughter of Vienna's grandfather Notary. Trojan was the result of a nephew/aunt breeding, Ch Foinavon Narcos (by Ch Seplecur Danny) ex Ch Seplecur Mist. Garbo had a litter by Ch Bokra Scenario, which had no affected hounds in it.

Other PRA cases have appeared in subsequent years, in each case the existing known carriers are behind the affected hounds. There was a father/daughter test mating onto Xile in New Zealand, which produced an affected. More recently a mass producer in England ignored the "never line breed to a known carrier" rule and had three litters from a Xile granddaughter to Xile great-grandsons. Ladestar Dorothea is therefore the carrier here; affected puppies came from the Ladestar V and W litters out of L. Mollie Malone.

Had PRA only appeared in "second rate" wolfhounds it is likely we could have removed it from the mainstream by now, but a little consideration will come up with major sires in top kennels worldwide who are closely related to these known carriers. Do we believe the mutation happened with the Witchesbroom Wizard litter? Was it his dam? We will never know, and it is unhelpful to guess unless you have PRA affected hounds to signpost the way. From the Witchesbroom H litter Himself and Huzzar were significant sires for the USA and Sweden, they do not appear as direct ancestors of PRA cases. From the Westmount C litter, three were carriers but Candor and Castor are not implicated behind known PRA cases to my knowledge.

Mary McBryde, then Mary Simmons, posited that W. Cauldron was the likely carrier line behind Sirius, as the Llonkyles kennel inbred onto Richelieu through Witchesbroom Sorcerer as well as directly onto Richelieu without problems appearing, then as now. Cauldron herself is behind major league kennels. It would be unfair to stigmatise her on the strength of what came through a grandchild who may not have inherited the defective gene from this direction. Alternatively, it could be that most of the Cauldron offspring used in breeding were not carriers - we will never know. She had a number of litters and no affected direct offspring, so is not a "known carrier". From her hundreds of American descendants, no reports of PRA.

Ch Seplecur Danny appears in the same position as Cauldron, as the grandsire of a known carrier, as does Ch Caredig Yankeedoodle. These were significant sires that were bred across a variety of carrier producer lines and never produced PRA. We may be cautiously optimistic that the carrier lines behind the Bokra H litter came via Notary and Ch Mist, although there is no proof. In normal circumstances Garbo's brother Ch Bokra George Caredig would have been treated as a possible carrier (he had a 50:50 chance of this) but due to his early success as the sire of the four Ballyphelan BB champions he was already being line bred to by the time Garbo's daughter was diagnosed. No one would have recommended line breeding to George, least of all his connections, but those who did risk it have gone some way to suggesting the dog was not a carrier, as he is not in the background of any cases of PRA. His descendants are behaving much as Cauldron's have.

NEVER MATE THE DESCENDANTS OF KNOWN CARRIERS TOGETHER

Now you have the names, we can move onto the avoidance. Until we have a blood test which can identify carriers Anne Janis will do a free risk assessment and show you the possibility of producing carriers or affecteds when you breed. Breeders worldwide are asked to stay alert for newly reported cases of PRA, as researchers need blood samples in order to work on identifying the faulty gene.

The very cautious will also avoid potential carriers, although this is becoming very difficult to do. I always mention Int Ch Solstrand Qvist at this point, as he was effectively test mated by never siring one case of PRA to four carriers - he can be treated as a clear dog despite being a 50/50 carrier "risk" on paper as an Xile son.

I seem to spend a lot of time on the telephone these days counting through the generations in line with what geneticists suggest we should do - restrict or refuse the use of males, where these descend from known carriers. After SIX generations of only breeding descendants down the generations to non-carrier lines the hound can be considered statistically "safe" as long as no other cases came up in the meantime. Bitches should breed through generations as fast as possible if otherwise of value to the breed, one litter one puppy bred on from was the desired method. In each generation the risk reduces as follows: 1:2, 1:4, 1:8, 1:16,1:32, 1:64. In the sixth generation, with the risk at 1:132 of the hound being a carrier, the hound could be considered "low risk" and be bred back into the general population and used in the same way as a non-carrier line. But it doesn't mean PRA has been bred out - just much reduced in risk.

Breeders have been extremely sensible, to put this into context there have been very low numbers of affected hounds. Could I ask everyone to remain vigilant? Do your risk analysis, check and recheck the pedigrees armed with all relevant information*. I have been thinking "we have been very lucky" - but it hasn't all been luck, as the great swathes of well bred litters leaving no descendants after 1990 testify. There have been many sacrifices made to get us to this point.

Liz Thornton


* IWHG Note: Many carrier dogs have now disappeared off five generation pedigrees, so it is easy to overlook a possible link. Please check your pedigrees and do a risk analysis before breeding. Contact Anne Janis for a confidential risk analysis.

To see some PRA carrier pedigrees please visit Liz Thornton's website.


                     
                     PROGRESSIVE RETINAL ATROPHY
                              Dogs with carrier status

Care should be taken not to put two of these together 
until they are beyond seven generations on the pedigree:

Ch Witchesbroom Sirius
Edeyrn Flame of Witchesbroom
Westmount Willie Fionncosach
Westmount Corona
Westmount Fargo
Westmound Carma
Westmount Xie-Xie
Westmount Xile of Mochras
Mochras Valentinian
Edelmar Mendell
Edelmar Freya
Ch Bokra Garbo
Bokra Vienna
Seplecur Trojan of Foinaven
Ladestar Dorothea
Ladestar Mollie Malone
Quadreaux Fitzgerald O'Hara
Ladestar's Quadreaux Torrance

 
 
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