Degenerative Myelopathy (DM) is a progressive disease involving the degeneration of the spinal cord, which affects 43 breeds of dog, including Rough and Smooth Collies. (source: Laboklin) The initial symptoms include ataxia (poor coordination) in the dog's rear, and dragging feet. As DM progresses the dog will eventually have difficulty standing, until it cannot walk. Sometimes the dog will develop urinary and faecal incontinence at the later stages. However, the disease is not painful. Prognosis from diagnosis is usually around 6 to 12 months.

In DM, the demyelination and axonal loss of the fibres in the spinal cord inhibit the communication of information and commands between the brain and the limbs, which causes the degenerative effect.

The disease usually affects dogs around 8 years of age (source: UFAW (Universities Federation for Animal Welfare) but can affect dogs that are younger or older.
 

DIAGNOSIS
A diagnosis of elimination is used to rule out other diseases that affect the spinal cord, using tests such as an MRI scan, myelography, and blood samples. The only method of definitive diagnosis is examination of the spinal cord during necropsy (clinical examination after death).
 

TREATMENT
There is no treatment or cure for DM.

GENETIC TEST
A genetic test for DM exists - which detected the gene is autosomal recessive, with incomplete penetrance. This means that dogs need two copies of the gene to be 'at risk' of expressing the disease, but even then the animal may not develop the disease.


The below chart is a theoretical breeding calculator for DM. Results in bold are results where the puppy will be 'at risk' of DM. Results that are 'around' a percentage means that each puppy has the quoted percentage chance of that result. It does not mean that EXACTLY that percentage of the litter will have the result. 
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FURTHER READING

UFAW - Degenerative Myelopathy in German Shepherds
Fitzpatrick Referrals - Canine Degenerative Myelopathy
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