Learn more about genetic testing for degenerative myelopathy and discover what Morris Animal Foundation is doing to help in the battle against this disease.
For many practitioners, degenerative myelopathy is a frustrating and heartbreaking disease. Frustrating because the diagnosis is a challenge and no treatment options exist beyond supportive care. Heartbreaking because of the disease’s relentless, cruel progression. However, the last decade has brought a quantum leap in our understanding of this disease, a new diagnostic test, and renewed efforts to find a treatment that could substantially impact the quality of life for our patients afflicted by DM.
Researchers have searched for a specific cause of degenerative myelopathy since the disease was first described 45 years ago. Morris Animal Foundation was an active supporter of many of these early studies, funding research focused on everything from vitamin deficiencies to viral infections. However, none of these avenues yielded a clear-cut cause for the disease.
Veterinarians have long recognized a breed predilection for DM. The advent of more sophisticated genetic tools in the early 1990s allowed researchers to explore the genetic underpinnings of the disease in greater detail. This, coupled with the discovery of a genetic mutation associated with amyotrophic lateral sclerosis in people, fueled more research to pinpoint a genetic basis for the disease. In 2009, researchers at the University of Missouri and the Broad Institute identified a mutation in the canine SOD1 gene as the likely culprit, opening a new era in our understanding of the disease and providing hope for a potential treatment.
A screening test for SOD1 (including a variant unique to Bernese mountain dogs) is available to veterinarians and dog owners. The test can help estimate the risk for disease development but must be interpreted with caution, since data suggests that other genetic or environmental factors also are critical to the development of degenerative myelopathy. In addition, not all breeds with the mutation have been proven to have disease susceptibility. According to the Orthopedic Foundation for Animals, breeds that have met this level of scientific evidence are:
- American Eskimo dog
- Bernese mountain dog
- Cardigan and Pembroke Welsh Corgi
- Chesapeake Bay retriever
- German shepherd dog
- Golden retriever
- Great Pyrenees
- Kerry blue terrier
- Rhodesian ridgeback
- Shetland sheepdog
- Soft-coated wheaten terrier
- Wire fox terrier
Although genetic testing can help with diagnosis of DM, definitive diagnosis can still be challenging. Commonly used diagnostic tools such as X-rays, magnetic resonance imaging and spinal fluid analysis have all fallen short in definitively diagnosing this disease. Morris Animal Foundation-funded researchers at Cornell University are exploring the use of an advanced MRI technique, diffusion tensor imaging. This tool may help detect subtle spinal cord changes and help in the diagnosis of degenerative myelopathy. This approach is successfully used to detect white matter lesion load in human patients with neurodegenerative disease. Early data using this new imaging technique in dogs is promising.
Despite promising advances in the diagnosis of DM and a greater understanding of how the SOD1 mutation contributes to pathogenesis, an effective treatment for DM remains elusive. Foundation-funded researchers at North Carolina State University are tackling this problem using a new gene silencing technology. In a small clinical trial enrolling four client-owned dogs with degenerative myelopathy, researchers are seeing if they can reduce the expression of the mutated gene using this new technique. If effective with no adverse results, researchers will explore this strategy further as a potential novel therapy for dogs with degenerative myelopathy in clinical trials.
As research continues, supportive care and physical rehabilitation remain the cornerstones of treatment for this disease.
For more information about our DM studies, visit Morris Animal Foundation. You also can subscribe to the Foundation’s new monthly email newsletter and podcast series, Fresh Scoop, geared toward practicing veterinarians. Fresh Scoop provides updates on the latest veterinary research findings on health advances that will impact your practice today, and shape veterinary medicine tomorrow.