|The history||To do||the future||the genetics||the gossip|
What is PRA ?
|PRA - progressive retina atrophy - it is a hereditary
eye-defect found in a lot of different breeds.
Even among wild living wolfs PRA has been found.
The disease develops slowly causing the retina, the light sensitive tissue in the back of the eye to degenerate and die. The affected dog slowly looses eyesight in the dark, and usually end up blind!!
In Papillons, however PRA develops extremely slow, and in such a way, so the dog often will NOT become completely blind - even at high age.
But the sight will start to deteriorate in a relatively young age, and a dog with a bad eyesight is not worth much in agility or obedience.....
Nevertheless, it is an unwanted defect in the breed, and breeders must make every effort, not to spread the gene by breeding dogs who are known to be genecarriers or are affected by PRA.
The gene is recessive and only if a dog
gets a gene from EACH parent, it will develop PRA.
PRA in papillons are a late onset form. The first signs can usually been seen by ophthalmologic examination at the age of 3-4 years, but they often are overlooked because the initial stages are so very-very faint. The bloodvessels are thinning and deteriorating. Later on a mirror like reflex are seen from the retina. Sometimes the owner will notice the dog to have some reluctance against going out in a dark yard, climbing stairs or generally moving around strange places in the dusk. But very often there are nothing at all, which makes anyone suspect problems with the dog's sight.
|the retina seen through the ophthalmoscopic instruments|
|Fig. 1. The normal retina. Note the many prominent blood vessels.||Fig. 2. A mid-stage PRA retina. Notice how the vascularity has been markedly reduced.|
Thanks to NetPets for the pictures above.
We have discovered a special opaque-grey-grenish shimmer from the
affected dogs eyes when exposed to flashlight. This opaque shimmer is well described in
veterinarian notes about PRA.
|The dog at the top is diagnosed PRA by ERG as 1½
The 2 in the middle are both ERG-cleared, the one to the left is 2 years, the one to the right is 7, and the one below is ophthalmologic cleared at 5 years.
Notice the different colorings of the eyes. The PRA-eyes are sort of
opaque, bottomless, the flashlight are being reflected completely by the degenerated
retina. The others are bright yellow to greenish, with no halo around. The pupils are well
defined, and not as wide open as in the PRA-dog.
|We just placed the dog at a table in the evening when the pupils were naturally dilated, and then shot some pictures using the flash - without the anti-red-eye-function - of course !!|
|Some rumors are saying PRA was "invented"
in Sweden. This is NOT true.
The gene-defect is not national, it is breed-specific!!
There have been diagnosed PRA in dogs bred in UK, USA, Norway, Holland, Iceland, Sweden and Denmark, but of course most PRA-cases are found in those countries, who thoroughly test their dogs.
In Denmark and Sweden the breeders can't get their puppies registered unless both parents have been tested clear of PRA within the last 12-month before mating. If a dog is diagnosed PRA, then it will be excluded from breeding as well as it's parents and offspring.
Back in '92 Pia Hansen, Gold Wings, started gathering
eye-test-results. Hoping to map the gene in order to prevent breeding dogs who were
carrying the gene.
To do ....
|As almost every papillon used for
breeding, are bred before the diagnosable age, which is believed to be
around 3 years, the problems are obvious.
Knowing about the genetics and the fact that we
are dealing with a recessive gene looking for carriers in a
pedigree in order to avoid them in ones breeding program makes very little sense.
test methods today are normal opthalmoscopy and in very few countries ERG.
By ERG the dog has to be anaesthetized. Then a special contact
lens are placed on the eye, and the eye are exposed to various light sources: glimpses,
red/blue and white. The eye/retina's responses to the light are recorded, and afterwards
these records are evaluated, preferably against a set of normal papillon retina-curves.
The diagnose is reliable at 95% at 2 year of age
|At the moment there are no way to test whether a dog
is genecarrier or not.
But in Denmark we have collected a lot of bloodsampels from familygroups suffering from PRA.
These samples have been send to proff: Simon Petersen-Jones who is researching in finding the causative gene.
Papillon Club America is sponsoring this research.
In time only a single bloodtest is needed to determine whether a dog is genetically free, carrier or will develop PRA.
As mentioned in the ECS-story - what we think we know today, may not at all be the whole truth, but remember: We are part of the future made today...
The only way the breeders can make a real effort avoiding the PRA-gene is by KNOWLEDGE!!! disclosure is the word - every bit of information can help the breeders map the gene in the pedigrees.
Visit our links site:the links below takes you to the breeders who co-operate in making this site and the PRA-list.
created and maintained by Pia Johansen
If you have any questions about PRA, please ask.
last update 20-11-08