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Degenerative Myelopathy (DM)
DM
DM aka Degenerative Myelopathy
How to Test for the DM Mutation
What is Degenerative Myelopathy (DM)?
Degenerative Myelopathy (DM) is a late onset progressive spinal/nerve disorder resulting in painless but permanent paralysis of the dog starting in the hindquarters and gradually moving forward resulting in loss of mobility and eventual organ failure as the myelin sheath of the nerves deteriorate.
The markers for DM have been documented in Collies as well as most other breeds. Current science is also pointing to the possibility of different variables of DM within different breeds. This area of testing definitely requires more research and this page is only intended to give an outline of the problem and the current information in relation to Collies. DM symptoms can mimic many other problems affecting hips or neurological disorders. It is generally not the ‘go to’ diagnosis but should be considered in situations where control of the rear legs becomes painlessly but progressively worse as the dog ages. Signs generally appear when the dog is over 7 years of age. Below is an image of a DM affected and normal spine. Image courtesy of www.caninegeneticdiseases.net.
The current test for DM is creating a great deal of concern for breeders of all breeds because this test is far from ‘cut and dried’.
The Orthopedic Foundation For Animals and the University of Missouri currently do not recommend testing of DM within the Collie Breed based on current research. There is still more study needed to understand how DM affects our breed.
If your Collie tests as At Risk do not consider it a doomsday sentence!
If you are an owner, a diagnosis of A/A or double carrier should not be a guaranteed heart breaking result. Know that in the history of the breed we have had many, many, many Collies with the same genetic make up of A/A or ‘at risk’ that have showed NO SIGNS of the disease before death. I currently have dogs that have tested as A/A or ‘at risk’ and I am not removing them from breeding based solely on this test. There is too much unknown and too many dogs that carry both mutations to use this test as a ‘deal breaker’ in removing dogs from the gene pool. Research is ongoing however the level of testing among Collie breeders is extremely low. I can guess that part of the reason for the low test rates may be due to the newness of the test and perhaps also because the test just does not give us an answer about quality of life for our Collies. Due to the lack of testing by breeders and the ongoing research needed, the problem of Degenerative Myelopathy has an unclear impact within the breed and in the individual dog at this time. It is not possible to know if a Collie with an A/A result will ever show symptoms of the disease.
This test is an indicator of the existence of the gene but is NOT a predictor of a dog being affected during its lifetime.
No one wants to see a dog succumb to this disease as the mobility of the pet is severely affected over time. In the latter stages, the dog is unable to control hind limbs and must be carried or potentially fitted with a wheeled cart to allow for mobility. While the disease is painless to the pet, the effect on owners can be significant as they see their companion gradually lose the ability to move on their own. There are no confirmed treatments or cures for this disease. While there are supplements and treatments that are being touted as potentially curative or palliative, scientific verification is extremely limited or non-existent.
As breeders, we want to be able to identify risk and to know if the risk is likely to impact quality of life. For Collies, this question is largely unanswered based on the current scientific information available. We are seeing a fairly high number of Collies either as carriers or double carriers of the disease and yet the reports of Collies suffering the effects of the disease are significantly lower.
I Should Avoid Buying an ‘At Risk’ Collie Right?
This question is why this test is so frustrating. The short answer for a Collie is ‘no’…because this test cannot tell us if the dog will ever develop symptoms. The long answer is ‘no’ because there are other major health issues that WILL have an impact on the life of a dog and the priority needs to be put on the likelihood of what will happen, not on the unverifiable chance of what could happen. I own multiple dogs with an ‘at risk’ result and I am not worried about them having symptoms from DM as they age.
I know I personally would love to eliminate this gene because it is an ‘unknown’ but the reality is I am more concerned about other health issues that ARE predictable. Because so many in the breed carry one or both genes, it is highly unlikely to ever be eliminated. If it did, we would have a major genetic bottleneck that would make DM seem like the least of our worries.
How Do You Test for DM and the SOD1 mutation?
Screening for the genetic anomaly is possible now thru several labs. Click HERE to learn more and review the testing process through OFA. Other labs in the USA will also perform the test however few labs are ‘approved’ by the Orthopedic Foundation For Animals (OFA) as a certified laboratory. Since most breeders look to OFA for a listing of all results when researching health history, results from an ‘unapproved’ lab will not be listed. While the testing may not be any less reliable, the ability to publicly list the results is limited or non-existent.
The current testing available screens for a mutation at the SOD1 location. While the terminology among labs may vary, if a dog is found to have two mutations, they are classified as ‘at risk’ for developing the disease. If only one mutation is found, the dog is a carrier and if no mutations are found, the dog is classified as ‘clear’ or a ‘non carrier’.
As noted above, even a Collie with two mutations is not expected to experience effects from the disease based on the current research.
While we have a test to identify the SOD1 mutation, this test cannot tell you if your Collie will be affected by DM. The only way to currently confirm DM is thru post mortem samples.
If you have made the difficult decision to euthanize due to suspected DM, PLEASE SUBMIT SAMPLES FOR TESTING to further help research on this disease in Collies. We have no clear correlation between A/A results and physical changes so post mortem samples are very much needed. Click HERE for information on sending samples.