Degenerative Myelopathy DM (Exon 1) Testing for Bernese Mountain Dogs in the USA

Bernese Mountain Dog puppies are a large, sturdy breed that falls within the American Kennel Club's working dog group. Originating from the Swiss Alps, they were originally bred for herding cattle and pulling carts. These dogs are easily spotted by their strong, tall build and their distinctive thick, tricolored coats. Known for their gentle and devoted nature, Bernese Mountain Dogs have become cherished family pets across the U.S.

These dogs are typically patient and calm, making them an excellent choice for families with children. Regular exercise is vital for this breed to keep them physically and mentally healthy. Their dense and heavy coats shed quite a bit, requiring frequent grooming sessions. Many American owners find investing in a powerful vacuum and grooming supplies essential to manage shedding effectively.

As with many large breeds, Bernese Mountain Dogs have a relatively shorter lifespan, typically ranging from 7 to 10 years in the United States. They are susceptible to several hereditary health issues which may influence their overall well-being and lifespan.

Among these inherited conditions, Degenerative Myelopathy (DM) stands out. This progressive neurological disease is linked to a specific mutation in the SOD1 gene exon 1, unique to Bernese Mountain Dogs compared to the more prevalent exon 2 mutation seen in other breeds. DM leads to progressive spinal cord degeneration and often impacts dogs over eight years of age, eventually causing paralysis.

What is Degenerative Myelopathy DM (Exon 1)?

Degenerative Myelopathy is a chronic, progressive spinal cord disease with multiple genetic variants. In Bernese Mountain Dogs, the disorder is caused by a distinct mutation in exon 1 of the SOD1 gene, differing from the common exon 2 mutation that affects numerous other breeds.

Initial symptoms typically start with hind limb weakness and ataxia, which is a loss of coordination affecting gait and mobility. Over several months to years, the condition worsens, leading to full paralysis of the hind limbs and potentially the forelimbs. Urinary and fecal incontinence are often observed in the disease's later stages.

Unfortunately, there is no known treatment or cure for DM. When mobility and quality of life decline significantly, humane euthanasia is often considered to prevent further suffering.

How is Degenerative Myelopathy Passed Down in Bernese Mountain Dogs?

This form of DM follows an autosomal recessive inheritance pattern, meaning a dog needs to inherit two copies of the mutated gene to be at a high risk of showing disease symptoms. However, some dogs with two copies of the mutation may never develop clinical signs due to incomplete penetrance.

• If both parents are affected, all puppies will inherit the disease.
• When both parents test clear, all offspring will be clear as well.
• Breeding two carriers usually results in about 50% carriers, 25% clear, and 25% affected puppies.
• A pairing of a clear and an affected parent produces all carrier puppies.
• A clear parent bred with a carrier typically results in approximately 50% clear and 50% carrier puppies.
• Breeding a carrier with an affected parent often yields 50% carriers and 50% affected puppies.

Why DNA Testing for Degenerative Myelopathy is Vital

Symptoms of DM appear late in life—usually after dogs have reached breeding age—making DNA testing a critical tool in guiding responsible breeding practices. The test classifies dogs into categories:

• Clear: No copies of the exon 1 or exon 2 mutations detected;
• Carrier: One copy of the mutation, typically asymptomatic;
• Affected/At risk: Two copies of the relevant mutations or one copy each of the exon 1 and exon 2 mutations, placing the dog at high risk for developing DM.

American breeders and owners are encouraged to request DNA testing from their veterinarians before making breeding decisions. Samples, often taken via cheek swabs or blood, are sent to accredited U.S. laboratories equipped for SOD1 gene mutation analysis.

Genetic screening is a cornerstone for reducing disease transmission and promoting healthier litters. Nevertheless, a positive genetic test alone is not a definitive diagnosis; clinical evaluation and exclusion of other neurological disorders remain essential.

Fostering Responsible Breeding and Ownership

Responsible ownership involves understanding the unique health challenges Bernese Mountain Dogs face and collaborating with American breed clubs and veterinarians focused on health screenings. Selecting breeding pairs without combined risks of DM (Exon 1) mutations helps decrease incidence over time.

Prospective owners interested in a Bernese Mountain Dog puppy should seek reputable breeders who provide health clearances, including thorough DM testing results. This practice supports the health and longevity of the breed while ensuring a rewarding pet ownership experience.

Summary

Degenerative Myelopathy DM (Exon 1) is a significant hereditary neurological condition affecting Bernese Mountain Dogs in the U.S., caused by a breed-specific mutation in the SOD1 gene exon 1. This disease leads to progressive paralysis predominantly in dogs over eight years old. DNA testing serves as a vital preventive measure for breeders and owners, helping manage this condition responsibly.

By emphasizing genetic testing, conscientious breeding, and early recognition, the Bernese Mountain Dog community in America can work together to reduce the impact of DM and enhance the overall quality of life for this wonderful breed.