What is DM:

Degenerative Myelopathy (DM) is disease that results in progressive paralysis of the hind limbs. DM is an old disease and appears in several breeds and even in "no breed" dogs.The first thing an owner can notice is the "dragging" with the hind foot. Later on the paralyses becomes more progressive and at the end also vital organs don't work right anymore.
This awful disease appears when a dog becomes older. That is why in the past there were a lot other diagnoses about dogs with paralyzed hind limbs.But now we knows that the genetic disease DM also can causes the deformation of nerves. And by test we can be sure when it is DM
(DM causes degeneration of the white matter in the spinal cord. The white matter is the portion of the spinal cord responsible for transmitting information between the brain and the body.)

How it looks when a dog has DM:
A movie of a CsW with DM:link
And after 4 months: LINK
When a dog can't walk nomal anymore an owner can choos for a brace: LINK
There are also weelchairs fo dogs with paralizsed hind legs: LINK

 The DM test:
There is a validated DM test for CsW. After test there can be diagnosed if a dog is Affected (= he has the mutation= DM/DM), Carrier (= he carries the mutation= N/DM) or Free (=N/N)
Because now there is a test we can find out how this disease is spread in the breed. In the meantime several CsW's are tested.
But we need a lot more CsW's for testing on DM!
Only then we can see how DM is spread in the breed and try to avoid that more Affected CsW's will be born!

Test results:
Several owners send (in the interest of the future of the breed) a copy of the test result for publication:
An update of DM test results you can find here

DM and the CsW breed:
Of the total population (about 5000 still living dogs) only an extreme percentage is yet tested for DM.
On this moment there are still a lot of breeding dogs not tested for DM.
But this does not mean that there is no DM in these lines!
DM is an "old disease" that appears in several breeds and also in "no breed"dogs
Not all dogs that are tested as Affected (DM/DM) will get physical problems when they become older.
Probably a combination of more factors causes if a dog will get physical problems.

DM and breeding:
Breeding of breed dogs is a closed system
When higher homozygote in a breed : more genetic diseases, more behavior problems, less resistor, weaker performance, less vitality, more birth dead, and smaller litters
Heterozygote is needed for a healthy population of a breed!
That is why specialists advices:
Try to breed as less Affected dogs as possible
But don't exclude dogs for breeding!
Try to keep the gene poule as broadly (and maximize) as possible

Finally:
There is not any reason for "blind panic" about the existents of DM in CsW breed!
Also in CsW breed it seems to be "an old disease" which did start in the past. Probably it was also in early lines in countries of origin and are a lot more CsW's (then we know now) Carrier or Affected.
So it will be good to test a lot more CsW's for DM!
Only then we can see how DM is spread in the breed and try to avoid that more Affected CsW's will be born!
It would not be wise on this moment to make breeding rules based on the relative low percentage tested CsW's. Because also a lot about DM is still unknown.
But for the future of the breed it is necessary tot test as much as possible CsW's.

And of course in the meantime a lot more research about DM is needed!