By Sandy Hodson
Hereditary disorders are of grave concern to any breed club. The disorder we have been most familiar with is hip dysplasia (HD) and we have worked hard as a club to eliminate this problem from our breeding stock. While there is still some distance to go, there is evidence that the rate of HD is declining in our breed through a diligent evaluation program. The evaluation program using radiographs has cost our breeders money, but the results have been worth it. We now need to give equal diligence to the eradication of the bleeding disorders von Willebrand’s Disease (vWD) and Canine Hemophilia Type B (CHB)
There are some significant differences between vWD and CHB that affect our ability to determine whether a dog is a carrier. With vWD, both males and females can be carriers and can be affected, showing symptoms of excessive bleeding. Von Willebrand’s Disease manifests itself differently in different breeds, but in the DD it is all or nothing — either the dog is severely affected or not at all. Beginning at the age of six weeks, a puppy can be tested for vWD and a clear determination can be made of its status with regards to the disease.
CHB is quite different. Females are carriers and never display the symptoms of excessive bleeding. It is only the males who are the bleeders. The extent to which they are affected may vary and thus they may not even be detected in a mild case. The symptoms usually show up by 18 months and the severity of symptoms usually increase with age. In litters where a male that is affected with CHB (but undetected) is bred to normal females, all of the female offspring will be carriers, while none of the male offspring will be carriers or affected. In litters where a normal male is bred to a female carrier, on average half the female offspring are carriers and half the male offspring are affected. The CHB status can be determined through testing in male dogs, but unfortunately not in the females.
CHB status in a female can be determined by two means: The first is progeny testing. With progeny testing a female is bred twice and all male puppies from the two litters are tested for CHB. Assuming at least six males were tested and if they all tested normal, then it can be concluded that she is probably not a carrier. The second means of determining the CHB status of a female is pedigree analysis. If the ancestors in the pedigree of the female and their offspring have been tested with no occurrence of CHB, then it can be concluded that the female is probably not a carrier.
So what does this mean for us as breeders and buyers of puppies?
When buying or breeding to a male DD, determine whether the dog has been tested and ask to see the results. The tests will be conclusive for both vWD and CHB. When buying or breeding to a female DD, the test is conclusive for vWD only. A thorough pedigree analysis would be necessary to determine CHB status. Many breeders have not done the progeny testing that would provide the information needed to do this.
Breeding a female that has not been determined NORMAL for CHB by progeny testing or pedigree analysis means that you are running the risk of selling female puppies that are carriers, with no way of knowing it. You must test the male offspring of two different litters (with at least a total of six males) to determine that she is not a carrier and that none of the males have been affected. If there are not enough males in two litters, then an additional breeding will be required to make a determination.
Ethically speaking, when selling female puppies your buyers should be informed if you have not yet been able to rule out CHB through either progeny testing or pedigree analysis.
As you can see, all of our breeders should be testing their puppies at six weeks of age in order for us to have the data to say with any certainty whether a particular female is a carrier or not. With this information we can make breeding decisions that will lead to the elimination of vWD and CHB in our breed.
Testing Procedures
The Cornell University Hematology Lab is the North American testing site for vWD and CHB (see “2001 Update on Hereditary Bleeding Disorders: von Willebrand’s Disease” in Drahthaar News September/October 2002). The testing process involves your veterinarian taking a blood sample from your dog(s), processing and freezing the sample, and then sending it to your nearest Canadian Veterinary College to forward on to Cornell University. This routing is necessary because the Colleges are able to get the blood through US Customs quickly enough that it does not thaw — a problem that some members experienced in the past when US Customs let the sample sit on a shelf for days.
There is no charge for the test itself. You will have to pay your vet for drawing and processing the samples and pay a processing fee to the Veterinary College. At University of Prince Edward Island this fee is currently $50. Multiple tests sent together at the same time, e.g., a litter, also cost just $50. As always, a consultation with your veterinarian a few weeks before you take your dog(s) in for testing would be wise to verify the process and costs in your area.
Puppies can be tested at six weeks by drawing blood from the jugular vein. This should be done prior to vaccinations or tattooing. This means that you will need to have a way of identifying each puppy by visual characteristics in order to match the numbered results to the appropriate puppy. A copy of both sides of the Ahnentafels for both parents should be sent with the samples for a litter.
Adult dogs that were not tested as puppies can be tested any time, but the dogs should be healthy and females should be out of heat for at least 8 weeks. A copy of both sides of the Ahnentafel should be sent with the sample for testing.
Yes, this process will add to the cost of having a litter and will consequently affect the price breeders must charge for their puppies. The value to both breeders and buyers should prove worth it. Only through diligent testing for blood disorders can we ensure that we are not inadvertently perpetuating a serious problem in the breed.
This article appeared in Drahthaar News, March/April 2003.
Permission to reprint this article may be obtained by contacting
Sandy Hodson, Tel.: 902-757-3116
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