Congenital Stationary Night Blindness in Briard Dogs: Causes & Testing

Congenital Stationary Night Blindness (CSNB) is a hereditary retinal disorder affecting Briard puppies, caused by a mutation in the RPE65 gene. This gene is vital for the retina's visual cycle, and the mutation leads to night blindness and, in some cases, progressive vision loss possibly culminating in permanent blindness.

The earliest symptom is night blindness, usually evident from 5 to 6 weeks of age. Affected dogs may hesitate to move in dim light but often retain usable day vision initially. However, visual impairment under daylight can develop over time, ranging from mild difficulties to profound loss. Some dogs display light brown patches on the retina visible between 2 to 3 years, reflecting retinal changes.

Understanding CSNB: Causes and Symptoms

CSNB results from a specific 4-base pair deletion in the RPE65 gene, disrupting the production of a crucial retinal protein. This genetic defect causes structural abnormalities in the retina's rods, which are responsible for vision in low-light conditions, explaining the primary symptom of night blindness.

While CSNB is typically termed "stationary," meaning it does not worsen rapidly, some cases see slow progression toward greater visual impairment with age. Importantly, the condition is not painful and does not shorten lifespan, but the vision challenges require consideration in daily care.

Who Can Be Affected?

Primarily, CSNB affects the Briard breed, with cases reported in major populations in France, the USA, and the UK. Mixed-breed dogs with Briard ancestry may carry one mutated gene but usually do not manifest clinical signs due to the autosomal recessive inheritance pattern.

Inheritance and Genetic Testing

CSNB is inherited in an autosomal recessive pattern, meaning that a dog must inherit two copies of the defective gene—one from each parent—to be affected. Dogs fall into one of three genetic statuses:

• Clear: Dogs with two normal gene copies, not affected or carriers.
• Carrier: Dogs with one normal and one mutated gene copy; they carry the mutation but show no symptoms and can pass it on.
• Affected: Dogs with two mutated gene copies, showing clinical signs of CSNB.

Breeding two carriers or two affected dogs risks producing affected offspring. To manage this, The Kennel Club in the UK administers a screening programme for responsible breeders.

How to Get Your Briard Tested

If you own a Briard or are planning to purchase one, it is vital to know the genetic status concerning CSNB. Testing involves collecting a DNA sample, mainly via a cheek swab or blood sample, which is sent to approved laboratories for analysis. Results are usually returned within 1 to 2 weeks.

Testing helps breeders make informed mating decisions to avoid producing affected puppies and assists owners in understanding their dog's condition and care needs.

Breeding Considerations and Responsible Ownership

Responsible breeders use CSNB testing to ensure dogs carrying the mutation are not mated together. This reduces the risk of producing affected puppies and helps improve the breed's overall health. Buyers are encouraged to inquire about the health testing status of Briard parents before acquiring a puppy.

Even affected dogs can have a good quality of life if their condition is mild. Awareness and early identification enable adjustments in the dog's environment and care to support their vision challenges compassionately.

Summary and Resources

Key points about CSNB in Briards:

• Caused by a mutation in the RPE65 gene resulting in night blindness and possible progressive vision loss.
• Inherited autosomal recessively; both parents must contribute the mutated gene for offspring to be affected.
• Genetic testing is available and recommended for breeders and prospective owners.
• The condition is non-painful and varies in severity.
• Responsible breeding and testing help reduce the incidence.

For more information and to find reputable Briard breeders who perform health testing including CSNB, visit The Kennel Club's CSNB Testing page.