Canine degenerative myelopathy is a condition of the spinal cord that causes a progressive weakening and loss of coordination in the dog’s hind legs, and can ultimately lead to paralysis. It is a hereditary condition that cannot be passed on or transmitted from dog to dog other than via their breed lines, and the condition occurs due to a fault in the SOD1 gene, a fault that can be found in a total of 43 different pedigree dog breeds.
Whilst the gene mutation that causes the condition can occur in a wide range of different breeds, it is not a notable problem in all of them, and only found to pose a significant risk of being widely spread in the breed lines of a much smaller range of dog types.
In order to curb the spread of the condition and stop it from being passed on through successive breed lines by affected dogs, The Kennel Club in association with the British Veterinary Association runs a health testing scheme for the condition. This scheme allows would-be breeders of affected breeds to test their dogs prior to breeding, and look up data of other dogs of the breed that have been tested too.
In this article, we will look at degenerative myelopathy as a hereditary health condition in more detail, including what sort of dogs can be affected by it, how the heredity of the condition works, and how to get your dog tested.
Canine degenerative myelopathy begins by causing a loss of coordination and generalised weakness in the hind legs, and affected dogs may drag one or both of their hind paws when they walk. In some cases, the condition can lead to paralysis of the hind limbs from the lower area of the spine downwards, which also commonly leads to urinary and faecal incontinence too.
Ultimately, the condition can also eventually cause the front limbs to become uncoordinated, atrophied and paralysed too, and lead to damage to the cranial nerves and respiratory muscles. Dogs badly affected are usually euthanized before they reach this stage, as the condition cannot be reversed or cured.
Precisely how long it takes for the condition to reach its ultimate conclusion can vary a lot from case to case-in some cases, the time between the onset of symptoms and paralysis may be under a year, while in others, it can take several years.
The gene mutation that causes the condition can be found in a total of 43 different dog breeds at the time of writing, however, only a small number of these breeds are badly affected by the more sever forms of the condition, to the point that pre-breeding health screening is advised.
In dogs that will be affected by the condition, it does not usually begin to present until the dog is at least seven years old, which means that owners of affected dogs may not realise that their dogs are going to develop the condition for many years-often, by the time the condition is diagnosed, affected dogs will already have been bred from, and so will have passed the condition on to their offspring.
Canine degenerative myelopathy is an autosomal recessive condition, which means that the likelihood of any given litter developing the condition will depend on what combination of genes they have inherited from their parent dogs.
If both of the parent dogs are tested clear for the condition, they cannot pass it on to their litter, while if both dogs have the condition, all of their litter will be affected.
Dogs that are not symptomatic for the condition themselves can still be carriers for the condition, and different combinations of breeding carriers with clear or affected dogs each produce different chances of their litter being affected, clear or carriers themselves.
Testing for degenerative myelopathy in at-risk breeds prior to breeding is very important, because the disease can be severe enough to lead to the need for the euthanasia of affected dogs. Additionally, because it is a fairly late-onset condition, one cannot assume that just because a dog has reached maturity without symptoms that they are clear of the condition.
To get your dog tested, you will need to ask your vet to take a DNA sample from your dog, which can be in the form of a blood sample or a buccal swab (a sample of the cells lining the inside of the dog’s cheek) which is then sent off to an approved laboratory for testing. The results will then be returned to the dog’s owner.
For a list of laboratories that are able to perform the test, check out this information on The Kennel Club’s website.