Canine degenerative myelopathy (DM) is a progressively
degenerative disease of the spinal cord which causes hind-limb
weakness, lameness and eventual paralysis. It appears to affect
dogs between the ages of 8–12 and the prognosis for total
paralysis is around 12–24 months.
With this disease, the myelin sheaths that normally protect the
spinal neurons disintegrate, exposing the underlying nerve fibres
and disrupting the communication pathways between the brain and
spinal cord. The precise cause of degenerative myelopathy is
unknown.
You can use the chart below to determine the possible status of
puppies from a breeding, with each parent being clear, carrier or
affected.
CLEAR
CARRIER
AFFECTED
CLEAR
Puppies will be 100% clear by parentage
50% clear
50% carrier
100% carrier
CARRIER
50% clear
50% carrier
25% clear
50% carrier
25% affected
50% carrier
50% affected
AFFECTED
100% carrier
50% carrier
50% affected
100% affected
CURRENT LIST OF TESTED DOGS AS PUBLISHED BY THE KC
HERE
Dogs can be tested with a simple buccal cheek swab at home and
sent to a laboratory, for example
Laboklin
.
Clear: Dog is negative for the Degenerative Myelopathy mutation.
Carrier: Dog carries one copy of the mutation associated with
Degenerative Myelopathy and could pass the mutation to its
offspring.
Affected – At Risk: Dog has a significantly higher risk of
developing DM and will always pass a copy of the mutation to its
offspring.
UNIVERSITY OF MISSOURI DM HANDOUT (PDF DOCUMENT) DOWNLOAD
HERE
There are several stages of the disease, and it can
develop quite rapidly.
Initially you may notice rear-limb weakness, muscle-mass
loss and dragging of one or both of the hind legs. I
didn't notice any dragging of the feet initially, but did
hear her nails scraping on the ground on hard surfaces.
You may also notice a change in their gait or them
standing cow-hocked.
DM has a slow onset and if your dog shows any sign of
pain, you are not dealing exclusively with DM.
Other conditions that can appear like DM require
different treatment and may require restricted exercise,
so it is important to ask your vet to examine your dog and
rule out other conditions involving the spine.
DM is almost unheard of in a dog under five years of age.
If you have a presumptive diagnosis of DM from your vet,
you can use a harness or sling to help your dog stand and
walk.
Boots can also protect their feet. I found the best ones,
only available from the US, were
these from DogBooties.com
.
If your dog has DM, you should continue with suitable
exercise to maintain muscle mass. Swimming, hydrotherapy
or walking in water can be effective in maintaining
muscle mass.
Not everyone will like the idea of a wheelchair, but
Teisha took to hers straight away. I found it excellent
for keeping her mobile when she started to lose the
ability to support her weight with her back legs.
She was still part of the pack and still enjoyed running
with the others and chasing a ball.
In the late and end stages of DM, progression is quicker.
It can plateau for a while, then forelimb weakness and
muscle-mass loss around the shoulders may develop.
Eventually the dog will be unable to stand or walk.
Weakness from DM can have secondary effects such as
pressure sores, systemic infections and urinary-tract
infections caused by urine retention.
A dog can pass naturally from end-stage DM, but care is
essential as kidney, lung or liver failure and
asphyxiation can eventually occur. This can be very
distressing for both the dog and owner.
Most people who care for their dogs through the later
stages will monitor them closely and choose euthanasia
when changes occur, to ensure the very final stage is not
reached.
The single nucleotide substitution in the gene called SOD1 that
causes Degenerative Myelopathy is autosomal recessive with
incomplete penetrance.
This means dogs carrying two copies of the mutation are at
increased risk of developing Degenerative Myelopathy during their
lives.
Dogs carrying a single copy of the mutation, also known as
carriers or heterozygotes, are less likely to develop
Degenerative Myelopathy as a result of the SOD1 mutation, but
they will pass the mutation to approximately half of their
offspring.
Breeding dogs that are less likely to develop Degenerative
Myelopathy should be the breeder’s priority, with a reduction in
mutation frequency across the breed being the secondary,
longer-term target.
Carriers can be bred from safely, provided they are mated to a
dog that has also been tested and is clear of the SOD1 mutation.
If a carrier is mated to a clear dog, approximately half of the
resulting puppies will also be carriers and should therefore be
tested before breeding.
Breeding carriers to tested clear dogs avoids affected puppies
while helping to maintain the genetic diversity of the breed.
However, the story of Degenerative Myelopathy is not that simple.
The disease has been confirmed in some dogs with only one copy of
the gene, suggesting other genetic or environmental influences
may determine whether a dog develops the disease.
Zeng R, Coates JR, Johnson GC, et al. Breed distribution of SOD1
alleles previously associated with canine degenerative
myelopathy. Journal of Veterinary Internal Medicine,
2014;28:515–521.
The University of Missouri found that an E40K missense mutation
of superoxide dismutase-1, or SOD1, is strongly associated with
this disorder.
SOD1 is a gene that encodes an enzyme responsible for destroying
free radicals in the body. Free radicals are reactive entities
that are part of the natural defence mechanism, but they become
harmful when produced in excessive quantities, causing cell
death and degenerative diseases.
The same gene mutation can also cause a form of human motor
neurone disease called amyotrophic lateral sclerosis. However,
the actual mechanism of the disease is still not clear.
Crisp MJ, Beckett J, Coates JR, et al. Canine degenerative
myelopathy: biochemical characterisation of superoxide dismutase
1 in the first naturally occurring non-human amyotrophic lateral
sclerosis model. Experimental Neurology, 2013;248:1–9.
Awano T, Johnson GS, Wade CM, et al. Genome-wide association
analysis reveals a SOD1 mutation in canine degenerative
myelopathy that resembles amyotrophic lateral sclerosis.
Proceedings of the National Academy of Sciences of the United
States of America, 2009;106:2794–2799.
DNA testing for the SOD1 gene identifies dogs that are clear,
carriers or at risk.
A clear dog has two normal copies of the gene. A carrier has one
normal copy and one mutated copy. An at-risk dog has two mutated
copies of the gene.
The test does not identify dogs that are clinically affected by
the disorder. It identifies dogs that are at greater risk of
developing clinical signs, although they may never do so during
their lifetime.
Ultimately, a diagnosis of Degenerative Myelopathy is made by
ruling out other diseases that cause progressive paralysis.
Samples of cerebrospinal fluid can be assessed for increased
protein levels. Advanced imaging may also be performed to rule
out other conditions.
DM causes insidious and progressive loss of muscle coordination,
known as ataxia.
The hind limbs are usually affected first by weakness and partial
paralysis. Owners may notice some or all of the following signs:
Dragging of the rear paws
Knuckling over on the rear toes
Sores on the tops of the paws
Wear on the toenails
Lameness
An unusual or spastic gait
Difficulty jumping, running, rising or walking
Balance difficulties
Muscle loss around the hindquarters
Paralysis of the rear legs
Incontinence
Possible front-limb paralysis
Three dog breeds have a particularly heightened risk of
developing or passing on the gene mutation associated with
canine Degenerative Myelopathy: the German Shepherd, Boxer and
Pembroke Welsh Corgi.
More than 40 breeds have been identified as having the propensity
to develop or pass on the mutation.
Males and females are equally affected and the average age of an
affected dog is approximately nine years. Younger dogs can be
affected, but this is uncommon.
Any dog can develop signs resembling DM. Being homozygous for the
mutation makes clinical DM more likely, but a clear or carrier
result does not guarantee that a dog will never develop a similar
neurological condition.
Many other conditions can cause rear-limb weakness or paralysis,
including disc disease, muscular diseases, other neurological
disorders, vestibular problems, injuries and age-related muscle
loss.
Any of these conditions can resemble DM, which is why veterinary
investigation is essential.
Exercise and other forms of physical therapy can help delay
disuse-related muscle loss and help affected dogs maintain
mobility and strength.
This may involve range-of-motion exercises, passive stretching,
hydrotherapy, swimming or the use of an underwater treadmill.
Your veterinary surgeon or qualified veterinary physiotherapist
should advise which exercises are safe for your dog.
A wheelchair can help a dog that has lost mobility in its rear
limbs, provided it can still use its front legs normally.
Your veterinary surgeon or physiotherapist can help you find a
suitable wheelchair and ensure it is fitted correctly.
No drug has been proven to stop the progression of canine DM.
Vitamins, omega-3 fatty acids and other supplements have been
suggested, but their effectiveness has not been established.
Experimental treatments may have adverse effects and should only
be considered under veterinary supervision.
A diagnosis of Degenerative Myelopathy is devastating,
and I can say that as an owner who has lived through it.
To find out that your dog has a progressive neurological
condition that will eventually lead to paralysis is
heartbreaking.
It is often hard to grasp the disease progression because
your dog is usually doing very well when symptoms are
first noticed.
You will have many questions: Is it going to hurt? How
long does my dog have? Can I do anything to slow it down?
Daily physiotherapy can help. A 2006 study found that
physiotherapy could extend a dog's life when DM was
suspected.
Physiotherapy may include active and passive exercise,
massage, hydrotherapy and protection for affected paws.
THERE IS NO CURE, BUT SOME OF THESE TREATMENTS AND
SUPPLEMENTS HAVE BEEN RECOMMENDED TO ME
Weekly hydrotherapy may be helpful as soon as changes in
gait are noticed.
Treatment might include swimming or an underwater
treadmill together with veterinary physiotherapy,
acupuncture or laser treatment.
Always discuss treatment with your veterinary surgeon.
Above all, keep your pet safely active for as long as your
vet advises.
If your dog starts to drag or knuckle a back leg, walking
on grass may reduce damage to the paws.
Rugs and runners can help prevent slipping on smooth
floors. Paw-protection boots may also help.
My experience with my own bitch began when I noticed
changes in her gait during August and September 2020.
She then started kicking one of her back legs out, so we
began hydrotherapy.
Unfortunately, she developed a hot spot which took months
to heal. By the time we restarted in January 2021, she was
very cow-hocked.
The vet confirmed my fears in March 2021, a few days
before her eighth birthday.
I kept her as active as possible. She loved to go out with
the other dogs, but as they were quite lively over the
fields, she would sometimes be knocked over. She was
therefore kept on a long lead for her own safety.
By July 2021 she was unable to go upstairs and struggled
with steps, although if we told her she could do it, she
would try.
She was still walking over the fields on soft grass so
that she did not graze her paws when dragging her back
leg.
She could come downstairs, but I held onto her so that she
did not slip or tumble.
Whilst I knew about DM because we had previously owned an
older dog with it, having a beautiful young bitch who, in
her own head, was still full of life was heartbreaking.
The video below was taken one month after the video above.
October 2021 — whilst Tei still had the use of her back
legs and could still complete one lap of the field, she
was no longer as agile.
Although I had said that I would never put her in a
wheelchair, it gave her back her freedom when going over
the fields with the other dogs.
June 2022 — my beautiful little girl was still so full of
life in her head, but her back legs were no longer able to
support her weight.
I know there are still breeders who have not experienced
DM in any of their Collies, and I was once unaware of how
many breeds are now affected.
One breeder told me that only American Collies were
health tested and clear of certain DNA-tested diseases,
which is untrue.
Another breeder who did not believe in testing asked what
she was supposed to do with DM at-risk puppies and thought
she would be expected to cull them.
I have had at least one DM at-risk puppy in a litter I
bred some years ago, before I was more aware of this
disease.
Had I known then what I know now, this could have been
avoided by using a dog clear of the DM mutation.
Sadly, this puppy also developed DM, which took her life
shortly before her tenth birthday.
There is no reason to exclude every DM at-risk dog from a
breeding programme.
If an at-risk dog is mated to a DM-clear dog, the puppies
will be carriers rather than at risk of inheriting two
copies of the mutation.
Breeding decisions should take account of health,
temperament, genetic diversity and current veterinary
genetic advice.
I am committed to raising awareness of this horrid disease
and have raised more than £1,000 for DM research in the
hope that one day there will be a cure.
Recommended walking aids
Biko Physio Brace:
HERE
Ensure you measure correctly, as it will not work
effectively if it is too loose or too tight.
You may find a second-hand wheelchair
here
or search for one in the UK
here
.
Unfortunately, we had to say our final goodbye to Tei on
10 November 2022.
She would have been ten years old the following March.
Gone far too soon — run free, my precious little girl.
If you would like to make a donation to the Cure4DM
Foundation, you can do so through PayPal using:
cure4dm.uk@gmail.com
Julie Growcott
HEALTH TESTING RESULTS AS PUBLISHED BY THE KENNEL CLUB
PLEASE NOTE THAT THIS LIST MAY NOT BE UP TO DATE. RESULTS ARE ONLY
UPDATED PERIODICALLY AND SOME BREEDERS CHOOSE NOT TO PUBLISH THEIR
RESULTS PUBLICLY.
Sources
Veterinary Centers of America
American College of Veterinary Surgeons
UC Davis
Washington State University
PetMD
VetInfo
Veterinary nutrition resources
NOAH Compendium
Dogs Naturally
Dr Conor Brady
This information is not intended to replace veterinary care.
Always follow the advice provided by your veterinary surgeon.
