This is advice for you the puppy buyer to take
wherever you go to look for a puppy, either here at
West Coast German Shepherds or elsewhere. If someone
is advertising or saying their dogs are
DM Free
or that they guarantee their dogs for DM,
please ask to see the actual DNA test results of the
parents. There are top level breeders out there
advertising DM Free puppies
and yet they are still
breeding two carrier parents to each other,
which means that some
puppies will get two genes and be AT RISK to develop
DM. There are also those out there telling their customers that their
lines do not have DM because they are German Lines,
this is not true!! Every German Shepherd is
susceptible to this disease no matter the
bloodlines, they must be tested in order to know if
they carry for it or not. No
matter what excuse they try to give you or what
story they come up with, the only way to know is if
they tested the parents of the puppies, SO ASK FOR
THE PROOF!! If they are advertising or saying they
are DM Free then they should readily show you the
proof of the testing done on their breeding dogs, if
they say or do otherwise then walk away if the
heartache of Degenerative Myelopathy is something
you are trying to avoid going through with your dog.
Canine Degenerative Myelopathy (also known as
Chronic Degenerative Radiculo Myelopathy) is a progressive disease of
the spinal cord in older dogs. The disease has an
insidious onset typically between 5 and 14 years of
age. It begins with *hindquarter weakness, rear limb
ataxia (reflex to right foot when turned backwards,
slow, or non existent), loss of balance, difficulty
rising or laying down, knuckling under while
walking, limp tail, rear legs crossing under body,
rear leg drag, spinal ataxia, hoarseness of bark,
leading to paralysis, and incontinence in the final
stages... The affected dog will wobble when
walking, knuckle over or drag the feet. This can
first occur in one hind limb and then affect the
other. As the disease progresses, the limbs become
weak and the dog begins to buckle and has difficulty
standing. The weakness gets progressively worse
until the dog is unable to walk. The clinical course
can range from 6 months to 1 year before dogs become
paraplegic. If signs progress for a longer period of
time, loss of urinary and fecal continence may occur
and eventually weakness will develop in the front
limbs. Another key feature of DM is that it is not a
painful disease.
c
Degenerative
Myelopathy is a devastating disease causing
progressive paralysis in a large number of dog
breeds. New research has identified a gene that is
associated with a major increase in risk of the
disease.
What
causes Degenerative Myelopathy?
Degenerative Myelopathy begins with the spinal cord
in the thoracic (chest) region. If we look under the
microscope at that area of the cord from a dog that
has died from DM, we see degeneration of the white
matter of the spinal cord. The white matter contains
fibers that transmit movement commands from the
brain to the limbs and sensory information from the
limbs to the brain.
In
the section of a spinal cord from a dog who has died
of DM (Left), the degeneration is seen as a loss of
the blue color at the edges (arrows) compared with
the spinal cord from a normal dog which is blue
throughout (Right).
This degeneration consists of both demyelization
(stripping away the insulation of these fibers) and
axonal loss (loss of the actual fibers), and
interferes with the communication between the brain
and limbs. Recent research has identified a mutation
in a gene that confers a greatly increased risk of
developing the disease.
How is Degenerative Myelopathy clinically
diagnosed?
Degenerative Myelopathy is a diagnosis of
elimination. We look for other causes of the
weakness using diagnostic tests like myelography and
MRI. When we have ruled them out, we end up with a
presumptive diagnosis of DM. The only way to confirm
the diagnosis is to examine the spinal cord under
the microscope when a necropsy (autopsy) is
performed. There are degenerative changes in the
spinal cord characteristic for DM and not typical
for some other spinal cord disease.
What
else can look like Degenerative Myelopathy?
Any disease that affects the dog’s spinal cord can
cause similar signs of loss of coordination and
weakness. Since many of these diseases can be
treated effectively, it is important to pursue the
necessary tests to be sure that the dog doesn’t have
one of these diseases. The most common cause of hind
limb weakness is herniated intervertebral disks. The
disks are shock absorbers between the vertebrae in
the back. When herniated, they can cause pressure on
the spinal cord and weakness or paralysis.
Short-legged, long back dogs are prone to slipped
disks. A herniated disk can usually be detected with
X-rays of the spine and myelogram or by using more
advanced imaging such as CT scan or MRI. Other
diseases we should consider include tumors, cysts,
infections, injuries and stroke. Similar diagnostic
procedures will help to diagnose most of these
diseases. If necessary, your veterinarian can refer
you to a board certified neurologist who can aid in
diagnosing Degenerative Myelopathy. A directory to a
neurologist near you can be found at
American College of Veterinary Internal Medicine
website under the "Find a Specialist Near You" link.
How do
we treat Degenerative Myelopathy?
There are no treatments that have been clearly shown
to stop or slow progression of DM. Although there
are a number of approaches that have been tried or
recommended on the internet, no scientific evidence
exists that they work. The outlook for a dog with DM
is still grave. The discovery of a gene that
identifies dogs at risk for developing Degenerative
Myelopathy could pave the way for therapeutic trials
to prevent the disease from developing. Meanwhile,
the quality of life of an affected dog can be
improved by measures such as good nursing care,
physical rehabilitation, pressure sore prevention,
monitoring for urinary infections, and ways to
increase mobility through use of harnesses and
carts.
Here the very well
explained graph of results from VET DNA CENTER when all progeny is
tested from one litter of a certain combination, thus even
when an At Risk parent is bred to a Carrier Parent, the result
can still be 50% or half of the pups born are clear
(fortunately) However, the other half will be at risk and not
worth the chance to take for any caring and careful breeder.
On the other hand,
if a breeder has a top rated male or female which tested AT
RISK, (do not panic) then when bred to a NORMAL mate only, this
combination will only produce CARRIER offspring, thus this
offspring can then be bred to a NORMAL mate, test ALL offspring
and choose pups which tested NORMAL only for furthering the
breeding program and thereby the breeder can quickly breed out
DM in its entirety.
This dog is homozygous N/N, with two
normal copies of the gene. In the seven breeds studied at the University
of Missouri in depth so far, dogs with test results of N/N (Normal) have
never been confirmed to have DM. This dog can only transmit the normal
gene to its offspring, and it is unlikely that this dog or its offspring
will ever develop DM.
Carrier (A/N)
This dog is heterozygous A/N, with one
mutated copy of the gene and one normal copy of the gene, and is
classified as a carrier. In the seven breeds studied at the University
of Missouri in depth so far, dogs with test results of A/N have never
been confirmed to have DM. While it is highly unlikely this dog will
ever develop DM, this dog can transmit either the normal gene or the
mutated gene to its offspring.
At-Risk (A/A)
This dog is homozygous A/A, with two
mutated copies of the gene, and is at risk for developing Degenerative
Myelopathy (DM). The research has shown that all dogs in the research
study with confirmed DM have had A/A DNA test results, however, not all
dogs testing as A/A have shown clinical signs of DM. DM is typically a
late onset disease, and dogs testing as A/A that are clinically normal
may still begin to show signs of the disease as they age. Some dogs
testing A/A did not begin to show clinical signs of DM until they were
15 years of age. Research is ongoing to estimate what percentage of dogs
testing as A/A will develop DM within their lifespan. At this point, the
mutation can only be interpreted as being at risk of developing DM
within the animal’s life. For dogs showing clinical signs with a
presumptive diagnosis of DM, affected (A/A) test results can be used as
an additional tool to aid in the diagnosis of DM. Dogs testing At-Risk
(A/A) can only pass the mutated gene on to their offspring.
Equivocal
An Equivocal test result indicates that
the test results were inconclusive. This is typically the result of poor
sample collection. When the test yields an equivocal result, a second
punch will be taken from the FTA card and the test rerun. If the second
test is still equivocal, the owner will be contacted and asked to submit
a new sample.
Owners with dogs testing as
Carriers (A/N), or At-Risk (A/A) are strongly encouraged to
share these results with their attending veterinarian and seek
genetic counseling when making breeding decisions.
The “A” (mutated) allele appears
to be very common in some breeds. In these breeds, an overly
aggressive breeding program to eliminate dogs testing A/A or A/N
might be devastating to the breed as a whole because it would
eliminate a large fraction of the high quality dogs that would
otherwise contribute desirable qualities to the breed.
Nonetheless, DM should be taken seriously. It is a fatal disease
with devastating consequences for the dog, and can be a trying
experience for the owners that care for them. A realistic
approach when considering which dogs to select for breeding
would be to treat the test results as one would treat any other
undesirable trait or fault. Dogs testing At-Risk (A/A) should be
considered to have a more serious fault than those testing as
Carriers (A/N). Incorporating this information into their
selection criteria, breeders can then proceed as conscientious
breeders have always done: make their breeding selections based
on all the dog’s strengths and all the dog’s faults. Using this
approach and factoring the DM test results into the breeding
decisions should reduce the prevalence of DM in the subsequent
generations while continuing to maintain and improve upon
positive, sought after traits.
We recommend that breeders take
into consideration the DM test results as they plan their
breeding programs; however, they should not over-emphasize the
test results. Instead, the test result should be one factor
among many in a balanced breeding program.
If you are a breeder looking to
ELIMINATE
the possibility of producing AT RISK
puppies in your breeding program, then breeding to a CLEAR
parent is the first step. By breeding your dog to a CLEAR
parent you are ASSURED
that EVERY
puppy produced from
that breeding will be
FREE of the
risk of developing Degenerative Myelopathy. Zamp Von Der Urbecke
has been DNA tested CLEAR,
therefore he
will never produce
any AT RISK offspring
no matter if he is bred to an
AT RISK
or CARRIER
female.
So what are you waiting for?
You can do your part in helping to reduce this debilitating
disease in our great German Shepherd breed by choosing to breed
your female to a CLEAR
tested male.
We have discovered a gene which is a
major risk factor for Degenerative Myelopathy (DM). In that gene, the
DNA occurs in two possible forms (or alleles). The "G" allele is the
predominant form in dog breeds in which DM seldom or never occurs; you
can think of it as the "Good" allele. The "A" allele is more frequent in
dog breeds for which DM is a common problem; you can think of it as the
"Affected" allele.
Summary: "A" allele is associated with DM; "G" allele is not associated
with DM.
Since an individual dog inherits two alleles (one from the sire and one
from the dam) there are three possible test results: two "A" alleles;
one "A" and one "G" allele; and, two "G" alleles. Summary: Test results
can be A/A, A/G, or G/G.
In the five breeds we studied so far (Boxer, Chesapeake Bay Retriever,
German Shepherd Dog, Pembroke Welsh Corgi, and Rhodesian Ridgeback),
dogs with test results of A/G and G/G have never been confirmed to have
DM. Essentially all dogs with DM have the A/A test result. Nonetheless,
many of the dogs with an A/A test result have not shown symptoms of DM.
Dogs with DM can begin showing signs of disease at *8 years of age, but
some do not show symptoms until they are as old as 15 years of age.
Thus, some of the dogs who have tested A/A and are now normal may still
develop signs of DM as they age. We have, however, found a few
15-year-old dogs that tested A/A and are not showing the clinical
symptoms of DM. Unfortunately, at this point we do not have a good
estimate of what percent of the dogs with the A/A test result will
develop DM within their life span.
Summary: Dogs that test A/G or G/G are very unlikely to develop DM. Dogs
that test A/A are much more likely to develop DM. Our research will now
focus on how many A/A dogs can survive to old age without developing DM
and why.
The "A" allele is very common in some breeds. In these breeds, an overly
aggressive breeding program to eliminate the dogs testing A/A or A/G
might be devastating to the breed as a whole because it would eliminate
a large fraction of the high quality dogs that would otherwise
contribute desirable qualities to the breed. Nonetheless, DM should be
taken seriously. It is a fatal disease with devastating consequences for
the dogs and a very unpleasant experience for the owners who care for
them. Thus, a realistic approach when considering which dogs to select
for breeding would be to consider dogs with the A/A or A/G test result
to have a fault, just as a poor top-line or imperfect gait would be
considered faults. Dogs that test A/A should be considered to have a
worse fault than those that test A/G. Dog breeders could then continue
to do what conscientious breeders have always done: make their
selections for breeding stock in light of all of the dogs’ good points
and all of the dogs’ faults. Using this approach over many generations
should substantially reduce the prevalence of DM while continuing to
maintain or improve those qualities that have contributed to the various
dog breeds.
Summary: We recommend that dog breeders take into consideration the DM
test results as they plan their breeding programs; however, they should
not over-emphasize this test result. Instead, the test result is one
factor among many in a balanced breeding program.
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