So why are all the conversation I've ever had with Malamute people about this, based on not breeding from a dog that has failed an eye test ?

Did it actually have a cataract when tested? If the breed is known to have hereditary late onset cataracts and it was diagnosed as being affected for a late onset cataract then no, of course it should not be bred from.

Or was the dog clear and it *may* get a late onset cataract in later life? If the marker gene has not been found and the breed suffers from a late onset hereditary cataract then they have problems. You can not stop breeding from all dogs else you would lose the breed, but if it didn't show up until after the age of 6 (which is when a bitch has to be bred from for the first time) then you have to breed from them before that age (obviously assuming they are a good example of the breed, have been hip scored with satisfactory results etc) and if they are found to have a hereditary late onset cataract then you do not breed from their offspring (and hope the marker gene is found!).

A cataract can be diagnosed as hereditary before the marker gene is found.

If they have failed an eye test then it means they have a hereditary cataract, it is possible for a dog to pass (and show as clear in the BRS) but still be affected for a non-hereditary cataract.

OK the dog has had a litter before, I think it's 4 or 5 years old. I spoke to the owner who had never done the relevant tests before and didn't know about them. I told her about the tests, and she has since done all the tests necessary.

I went when the dog was tested and it came back as having late onset. I looked too as did the owner so we could both see what he was looking at and it showed up very clearly.

In that breed he said they had no marker for late onset, only for Juvenile.

The owner then had it DNA tested and it came back as clear for JHC, but she wants to breed from the dog again, knowing it failed an eye test for late onset, saying that as they don't know whether it's hereditary or not, she's willing to take the chance !

If that makes sense.

How so, when the marker to determine whether it's hereditary hasn't been found yet ?

If it is signed as Affected, how can it be recorded as clear..........I don't understand !

Right - this makes a bit more sense. It still depends on the breed, if it is the breed I mentioned before then they are predisposed to hereditary LHC and thus she should not be bred from again.

However as mentioned previously, not all late onset cataracts are hereditary - it is breed specific. Some senile cataracts are merely due to old age. If she has been recorded as being affected for LHC and she is a breed predisposed to hereditary LHC then she should not be bred from again.

I'll address the issue of the marker gene in the next post.

Right, you do not need to find the marker gene to know if a disease/condition is hereditary or not. What you do need is sufficient information to identify that a particular condition is inherited. If an affected dog produces affected offspring (and this comes up several times) then you know a condition is hereditary. You then need to take several DNA samples of affected dogs and compare them to samples of unaffected dogs to try and identify where the gene differs. This process can take years. Therefore you can know that a condition is hereditary long before you are able to produce a DNA test for it.

This will only happen when a dog is clear for any hereditary cataract but has a non-hereditary cataract.

OK thanks.

I don't know if LHC is predisposed in Bostons !! The Boston in question is owned by a lady that lives in my neighbourhood, and unrelated to my friends dogs (thank god) ! I didnt want to mention the breed earlier because if she came on here, as she does, I know she would think people will mistake the query as being about her dogs, as she knows I post about her dogs on here.

Ok, so for example, in the case of a Malamute........if an unaffected Mal is bred and produces a Mal with HC, but then later down the line the Dam is recorded as Affected, does this mean it is hereditary but that it passed as a cautionary clear, or that it was completely undetected beforehand ?

A Non hereditary cataract being that the dog has it but the parents dont ? Is that right ?? Because if that's the case, maybe it just hasnt been detected in the parents yet, but come out in the progeny sooner !

I'm just trying to get my head round it !

Yes it is, take a look at the following excerpt: