Eye test HC

i have been researching a puppy's genetic health history on the KC website. The grandfather had an eye test result of "HC affected" at the age of 9 years. Is there a test (other than annual eye test) to know if the father of the puppy also affected? The father has had annual eye tests for the for 8 years that are all clear, but could he be affected?

 

There is a genetic test for HC (Hereditary Cataracts). Given the family history it'd be the right thing for the breeder to make sure the parent dogs have been genetically tested. Personally I'd want to see the genetic test results, not just eye test results. Eye tests won't show a result until symptoms develop. The genetic test will tell you for sure.

Since the grandfather was affected that means that he had two copies of the gene that causes this problem - he got one from each of his parents. A dog needs two copies of this gene to actually get symptoms of the disease. He would have passed on one of these genes to all of his offspring. So his son, the father of the litter you are considering, will have a copy of this gene. If the father has only one copy he will not actually get the disease himself but he may pass this gene on to a puppy.

If the mother of the litter has no copies of the gene then the worst that can happen is that the puppies will be carriers, because the only copy they can inherit is one copy only from their father. One copy of the gene is not enough to get the disease. But if the mother does also have copies of the gene (even just one) then some of the puppies may be affected (as in, they could inherit two copies of the gene and then will show symptoms later in life).

So, as a minimum you'd want to see that the mother tests totally clear of the genes that cause this disease.

I hope that makes sense Genetics can be confusing....

 

Thank you, that makes so much sense, I thought the test sounded suspicious.

 

It's possibly just that the eye test is 'outdated technology'. Before genetic testing things like eye tests (or just waiting for symptoms to show up) were all we had to rely on. But times have moved on and breeders should be using genetic tests where they're available.

Even if things don't work out with this litter there'll be a more savvy breeder with a lovely, healthy pup out there for you

 

There is no DNA test yet available for HC in Labradors so we have only the yearly eye tests at the moment. The Animal Health Trust is doing a lot of research into the subject and working on developing a commercially available test for the disorder.

 

That's a shame. The genetic markers must be varied and breed-specific. Hopefully it's only a matter of time before a DNA test is available for Labradors.

Sounds like the annual eye certificate is the only option then. You could ask about the mother's ancestors to see if there has been any eye testing done on that side or any evidence of the disease in her family (doesn't rule out being a carrier though).

 

Hi - we are going to get a chocolate lab puppy which is only just a week old, the person selling it has just discovered that the Dad has has failed the HC eye test (he was clear last year) but the Mum is fine. Am I then right to assume that this is a dormant gene in the puppy and it will not be affected, but should not be breed from? Many thanks

 

I assume you mean the puppy is one week old now, but you won't be getting it until it is eight weeks, right?

I'm no expert, but from the conversation above, it sounds like there is no genetic test available for Labradors, so it's just a case of relying on the yearly eye tests. If the sire is affected, I would be quite worried, to be honest, because even if them dam isn't at this stage, it could develop later (as it has in the sire), which would mean there is a chance that the puppy will be affected (not just a carrier). If she is clear of the genes, she is fine, but without a test, there is always a bit of a gamble. All you can do is look back through the history on her side and see if there are any affected dogs and work through from there.
With no genetic test available, I wouldn't breed from a dog I knew (or suspected) was a carrier, because you couldn't be 100% sure that the bitch you were using was clear.