Unfortunately, there is a breed predisposition to Degenerative Myelopathy, and German Shepherds, Rottweilers, and Labrador Retrievers are the most common breedds to experience this syndrome. This is a disease of unknown cause (other than genetic) that occurs as large breed dogs age and their spinal cords fail to perform their proper duties. It (as of now) is an irreverasble condition, and eventually results in paralysis of the rear limbs. It is also a very sad disease as the pets are quite aware that they seem fine, but they cannot walk. Newer genetic testing that is now being developed may help identify the genes that cause this disease, but we have yet to determine why it happens. Hopefully an answer is in the works very soon in the future. We have determined that it is not an infection, or fungus, bute we still don't know the cause.
You have my deepest empathy for the loss of your pet.
Hopefully the new DNA mapping occuring right now will have answers in the future.
Dr. G
Dog Veterinarian
Chief of Staff, Senior ER Clinician