The Orthopedic Foundation for Animals has a DNA saliva test to screen for the mutated gene that has been seen in dogs with degenerative myelopathy. Now that a test is available the disease can be bred out of breeds with a high preponderance. The test is only recommended for predisposed breeds, but can be performed on DNA from any dog on samples collected through swabbing the inside of the animal’s cheek with a sterile cotton swab or through venipuncture.
The test determines whether the mutated copy of SOD1 is present in the DNA sample submitted. It must be interpreted with caution by a veterinarian in combination with the animal’s clinical signs and lab test results.
TEST RESULTS
Normal / Normal (N/N, or ‘clear’): The dog does not have the mutation and is extremely unlikely to develop degenerative myelopathy. There have been cases, however, in which dogs that tested clear were found to have DM upon necropsy.
Normal / Abnormal (N/A or ‘carrier’): The dog has one mutated copy of the gene (is heterozygous) and is a carrier but will not have degenerative myelopathy though there has now been some cases of heterozygous carriers developing DM. It will be possible for it to pass the mutation to offspring. A thorough examination of the dog’s pedigree and DNA testing should be undertaken prior to breeding a dog with this result.
Abnormal / Abnormal (A/A or ‘At Risk’): The dog has two copies (is homozygous) for the mutation and is at risk for degenerative myelopathy.
GENETICS
Breeding risks for degenerative myelopathy can be calculated using the Punnett Square:
If both parents are clear (N/N) then all of the puppies will be clear.
If one parent is a carrier (N/A) and one is clear (N/N) each puppy has a 50% chance of being clear and a 50% chance of being a carrier.
If both parents are carriers (N/A) each puppy has a 25% chance of being clear (N/N), 50% chance of being a carrier (N/A), and 25% chance of being affected and carrier (A/A)
If one parent is clear (N/N) and one parent is affected (A/A) then all puppies will be carriers (N/A)
If one parent is a carrier (N/A) and one is at risk (A/A) each puppy has a 50% chance of being a carrier(N/A) and 50% chance of being affected and carrier (A/A)
If both parents are at risk (A/A) then all puppies will be affected and carrier (A/A)
SYMPTOMS
Degenerative myelopathy (DM) is a terminal disease. It mimics symptoms arthritis or back pain and initially affects the back legs. As the disease progresses it continues to cause muscle weakness and loss, and lack of coordination. At first, the dog looks wobbly and may drag one or both rear paws when it walks. The dragging of the paws leads to its own issues (worn down nails or cuts on the paws from dragging). Eventually it leads to extensive paralysis of the back legs. The disease then usually progresses to incontinence, difficulty balancing and walking, front limb weakness and paralysis, and extensive muscle atrophy and paralysis. Once the cranial nerve or respiratory muscle involvement deteriorates, most people opt for euthanasia. Some sooner than needed, as there are options available to keep the quality of life optimal.
The progression of this disease is highly variable meaning that the dog could be crippled within a few months, or may survive as long as three years or more.
CAUSES
The etiology of this disease is unknown. Recent research has shown that a mutation in the SOD1 gene is a risk factor for developing degenerative myelopathy in several breeds. Most people are familiar with Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig’s disease). The pathological spinal lesions of ALS are similar to those of canine DM. Many other spinal cord dysfunctions (disc disease, tumors, etc.) should be ruled out before accepting the diagnosis of degenerative myelopathy.
TREATMENT
There is no cure for degenerative myelopathy. Currently, it is progressive and irreversible with no cure. There also have been no treatments that have shown to stop or slow progression of DM. But again the disease is highly variable and there is hope.
Here are some products or devices to help with DM. For the dragging of the back legs that lead to bleeding nails and paws, you can purchase booties and hock joint supports for the hind legs. When the dog needs a little lift, you can purchase a belly lifting harness and a hind lifting harness to help. If you notice incontinence/leakage, you can purchase these diapers. While wheelchairs are important for exercise, you can also take your pup with you on walks or bike rides by purchasing a doggy trailer/jogger.
EXERCISE
Exercise is important and recommended to maintain the dog’s ability to walk and increase survival time. Swimming or hydrotherapy is very beneficial. Purchasing a belly sling or hand-held harness helps to support the hind legs. A 2 or 4 wheel dog cart, or “dog wheelchair” helps the dog to be mobile for longer.
Wheelchairs are pricey. However, there are non-profit organizations, such as Tyson’s Wonder Wheels 4 Boxers that fund-raise to provide wheelchairs for boxers in need. It is important that you invest in a good wheelchair for your boxer. I purchased a wheelchair and was only told by my veterinarian later that it would do more harm than good 🙁
Tyson’s Wonder Wheels 4 Boxers is a non-profit so 100% of any donation given is put toward the cost of the wheelchairs. All of us here know that times are hard right now with all the negative things going on, please know that even a $2 donation helps a boxer in need be mobile again. If you would like to donate, click here.
PREVENTION
This is some research I was doing to find out what can be done so more dogs can be prevented from having DM. It is preventable with certain tests. Most reputable breeders have had these tests done before they produce litters. If you are thinking of breeding your Boxer it may be a good idea , in fact it IS a good idea to have these tests run first. In the long run we wouldn’t have to be doing fundraisers to provide wheelchairs.
Article written by Linda Searle and Dayna Russo