URIC ACID EXCRETION/ CANINE HYPERURICOSURIA/ HUU
This is a problem which has recently been discovered in the HWV. Affected dogs excrete uric acid which can lead to the formation of urinary calculi (stones) which sometimes require surgery to remove.
A gene mutation has been found to cause this which has a recessive mode of inheritance. This means that both of the pair of genes the dog has have to be the mutated gene to be affected by the disorder. DNA testing can classify dogs as either clear (not carry the mutated gene at all), a carrier (carry one copy of the mutated gene) or affected (carry two copies of the mutated gene). It should be noted that not all dogs who are genetically “affected” will become affected by the problem. Neither clear or carrier dogs will develop the disorder.
When dogs are mated each parent passes on one copy of the gene to form a pair with the gene passed on from the other parent. Clear dogs cannot pass on the mutated gene so none of their progeny will be affected. Carrier dogs pass on the mutated gene in an average of 50% of cases and affected dogs will pass on the mutated gene 100% of the time.
Therefore on average the matings below will produce puppies in the proportion:
Clear x Clear = 100% Clear
Clear x Carrier = 50% Carrier, 50% Clear
Clear x Affected = 100% Carrier
Carrier x Carrier = 25% Clear, 50% Carrier, 25% Affected
Carrier x Affected = 50% Carrier, 50% Affected
Affected x Affected = 100% Affected
It seems likely that this is not a new problem and no doubt there are plenty of genetically “affected” dogs who never have a problem and whom we are not aware of. However, whilst not all “affected” dogs will have clinical signs or develop problems it would make sense since we can genetically test for status to try to eliminate the problem by selectively breeding the mutated gene out. This way we could eliminate the problem entirely. One of the problems the breed has is a small gene pool so breeding this out quickly may prove more difficult than is ideal. It is very important we don’t place all our emphasis on eradicating this problem and create another one by narrowing our gene pool considerably further.
In order for the HWVA to give the best information possible with regard to what steps we should be taking to eradicate the problem, we really need to get a better idea of the genetic status of the breed in this regard. What we are suggesting is that anyone with dogs that will be bred from have their DNA tested. This involves simply taking a swab of the inside of the cheek (this can be done using a kit supplied to you if the test is ordered through the AHT). The sample is then sent to be analysed and results sent out within a few days. Further details can be found here. Kennel Club Assured Breeders can get a discount on the cost of DNA testing. Dogs who are profiled “affected” can be monitored more closely to look for signs of disease.
We would be able to build a bigger more accurate picture of the breed’s genetic status if we had access to the results on a confidential basis and we would strongly encourage this openness with us. At the very minimum if we were made aware of dogs with a clear status we may be able to build a picture of how feasible it will be to eradicate this problem easily. The idea being clear dogs will never produce affected despite who they are paired to. They can be freely used on carrier dogs without risking producing an affected and any puppies likely to be entering a breeding program from a mating can be tested so that clears can be preferentially selected. Obviously clear to clear matings would produce all clear offspring. Given that we need to be very careful to keep an amount of genetic diversity to discourage other issues taking hold it is only as more HWV are tested that we will get a clearer picture of the best guidance to give to allow the breed to move forward.
Dogs who aren’t part of a breeding program can naturally be tested to ascertain their status for the owner’s peace of mind. However, our focus is to reduce the occurrence through selective breeding which would only apply to dogs in a breeding program. Should breeders discover they have mated two affected dogs so all offspring would have an “affected” status we would encourage them to inform puppy owners so that they have an idea of what to look out for.
For people looking for a puppy… choosing from a breeder who has tested for this mutation and used at least one clear dog allows them to be completely sure their puppy will not develop this genetic disease at any point.
We very much hope that everyone involved in breeding the HWV will join us in trying to eradicate the problem and testing so they can employ informed mating decisions.
|The HWVA is no longer able to offer a refund on HUU testing due to the ongoing cost involved. We are very pleased to see a large number of breeders embracing the use of the tests to allow them to make better informed breeding decisions.|
The HWVA can obtain a 5% discount on the purchase of the swab kit from the Animal DNA Diagnostics. Please contact firstname.lastname@example.org for the code.