Degenerative Myelopathy in Bernese: Is the current OFA DNA Test the Answer?
By Kevin Curran, MD
February 3, 2009
There is a growing concern regarding the recently developed DNA test for Degenerative Myelopathy (DM) now offered by the OFA. By way of background, DM is a syndrome of clinical findings rather than a disease. This is an important distinction because many clinicians and researchers suspect that DM is actually caused by more than one disease process. Few, if any, clinicians and researchers feel that DM has been definitively characterized clinically, radiographically or pathologically in any dog breed. This lack of diagnostic assurance directly impacts the work to find a DNA test for DM or any other disease. If you do not have the phenotype (clinical presentation and diagnostic requirements) defined then it is impossible to know if the genotype (the DNA make-up) is correct.
An example of the importance of accurate phenotype diagnosis is found in canine lymphoma. The diagnostic classification of canine lymphoma is completely different from human classification. Attempts to apply human treatment to canine tumors have failed in no small part because of this discrepancy.
Human lymphomas are classified according to the WHO (World Health Organization) classification of lymphomas. This is a fairly complex classification scheme based on pathologic appearance, a series of special histopathologic markers and tumor spread. Specific treatment protocols have been developed based on this classification system and clinical results have improved significantly.
Canine clinicians and researchers have recognized the importance of classifying canine lymphomas via this regimen and an AKC CHF grant has been started to perform this complex task. This grant has been supported by the BMDCA through its CHF Donor Advised Fund. It is hoped that when this classification is completed, the phenotypes characterized, the treatment successes seen in human medicine will then be translated into canine treatment improvements
Currently, for $65, the OFA offers a DNA test for DM that was developed at the Univ. of Missouri. This test is for a mutation of DNA that, at best, has been found to be associated with DM in one breed. They do not know if this mutation is causative for the disease in any breed. They only know it is associated with dogs diagnosed with DM in one breed. Based on the information Dawn Gabig presented in an earlier email, the numbers of samples processed for various breeds is too small to draw any conclusions other than those just mentioned.
There is no meaningful data for the OFA DNA test for DM in the BMD. It has not been shown to be associated with DM in the BMD and there are too few samples evaluated to begin to draw conclusions regarding the applicability of this test in the BMD.
There are currently two research studies supported by the Canine Health Foundation that are pilot projects to better define the clinical, radiographic and pathologic entities that make up DM in all breeds. These studies are accepting affected dogs to be enrolled in their protocols. A separate CHF study, from which the OFA DNA test for DM was developed, is also recruiting DNA sample submissions from affected BMD's.
This begs the question, what should the average BMD owner do? The answer
right now is nothing. If you pay $65 and send DNA in from your BMD you will
get one of the three following results:
. Your dog has both mutations for the DNA
. your dog has one mutation and one normal gene for the mutation
. Your dog does not have the mutation for the DNA.
Unfortunately no one knows what any of these results mean in the BMD (or any
other breed). No one can say that having two mutations actually means your
dog will get DM, or that one mutation means your dog may or may not get DM.
In fact, no one can even say that a dog lacking a mutation at all will not
get DM.
To summarize:
To proceed with discerning the DNA associated with a disease process, as has been done in human medicine with lymphomas, it is first critical to classify the pathologic appearance, symptoms, histopathology and other characteristics of the disease process being studied.
There is no reason to spend any money on a test that offers absolutely no answers.
If you have a dog affected by symptoms commonly associated with degenerative myelopathy and your pursuit of veterinary assistance has lead your veterinarian to believe it's likely the dog has DM, then you should contact the CHF studies to try to enroll your dog in these studies. You should not have to pay to have this DNA test done to be a part of these studies. Hopefully, some BMD dog owners will agree to have necropsy samples submitted to these studies, as this is the only way definitive information will be developed regarding this syndrome. Dog owners of relatives of affected dogs eventually may be asked to submit DNA samples as part of these research projects. There should not be a charge for these DNA tests either.
For owners and breeders interested in useful information on the hereditary nature of DM, at this time financial resources of would be better spent in research than on applying the OFA Test for individual dogs. At this time there is simply not enough known about this mutation to make any breeding decisions or assumptions of susceptibility for acquiring DM based on the test being offered by the OFA.
I recognize the devastating impact that DM has on both the animal and its family. Unfortunately there is nothing available that has any positive impact on this process nor is there anything in the immediate future. Owners of dogs affected with DM need to keep in mind that although symptoms may have improved, temporarily, by various treatments the disease process itself is progressing. These dogs are an important part of defining the DM disease(s) involved. I implore any owner of an affected dog to contact the researchers to participate in research studies.
Joan R. Coates, DVM, MS is the principle investigator on all three grants researching DM supported by the AKC CHF. She can be reached at CoatesJ@missouri.edu
Last modified: February 6, 2009.