Congenital Stationary Night Blindness (CSNB) in Briard dogs

Congenital stationary night blindness (CSNB for short) is a hereditary health condition that affects the eyes, and which has been identified in the Briard dog breed. The condition occurs due to a mutation in the retinal pigmentation of the eye in one of the protein genes, which causes dysfunction of the retina and the accumulation of lipids in the retinal pigmentation, generally around the tapetum lucidum, the part of the eye that reflects light.

The condition leads to night blindness in affected dogs well as a range of other visual problems, and can cause permanent and irreversible blindness. Congenital stationary night blindness can be much more pronounced in some dogs than others, with some only being very lightly affected and otherwise, having a good quality of life and normal lifespan.

In order to reduce incidences of the condition in the Briard breed and prevent the condition from being passed on down through the breed line to ever more dogs, The Kennel Club oversees a screening programme to allow Briard breeders to test their dog for the markers of the condition prior to breeding, in order to make an informed decision on whether or not to breed from them.

In this article, we will look at congenital stationary night blindness in the Briard in more detail, including how the heredity of the condition works and how to get your dog tested. Read on to learn more.

More about congenital stationary night blindness

Congenital stationary night blindness is often confused with progressive retinal atrophy before firm diagnosis, but while progressive retinal atrophy always leads to a slow, progressive march to full blindness that is irreversible, congenital stationary night blindness may not be total, and in some dogs, only has a very small impact on their vision.

The condition is not painful or dangerous in terms of shortening the animal’s lifespan, and dogs that are not badly affected with the condition can enjoy a generally normal quality of life. Some dogs, on the other hand, may become completely blind due to the condition, which usually becomes self-evident from a young age.

The condition occurs due to a gene mutation that causes structural changes to the outer sections of the rods of the eyes, as well as causing inclusions (marks or debris) to appear in the epithelial pigmentation.

What sort of dogs can be affected by the condition?

Congenital stationary night blindness can be found in the Briard dog breed, and has been widely identified in countries with large populations of Briard dogs, such as France and the USA.

While Briards are not as common in the UK as many other breeds, UK Briards can of course be affected too, particularly given the fact that they often share ancestry with imported dogs from France.

Cross breed dogs with some Briard ancestry can potentially inherit one of the faulty genes that cause the condition from the Briard side of their ancestry, but due to the hybrid vigour that results in outcrossing to an unrelated breed, it is uncommon for mixed breed dogs to be affected with the active form of the condition.

How does the heredity of the condition work?

Congenital stationary night blindness is a hereditary health condition, which means that it cannot be caught or transferred from dog to dog other than by means of heredity. In order for a dog to inherit the condition and be affected by it, they need to inherit a specific combination of the faulty gene from both sides of their ancestry.

Congenital stationary night blindness is inherited by means of autosomal recessive heredity, meaning that a dog must inherit markers for the condition from both of their parents in order to be affected by or a carrier for the condition. Dogs are assigned to one of three statuses: clear, carrier or affected.

• Two clear dogs will have all clear offspring.
• Two affected dogs will have all affected offspring.
• Two carrier dogs will have 50% carriers, 25% affected and 25% clear.
• A clear dog and a carrier will have 50% carriers and 50% clear.
• An affected dog and a carrier will have 50% carriers and 50% affected.
• An affected dog and a clear dog will have a litter of carriers.

How to get your dog tested

If you own a Briard and intend to breed from them, it is important to ascertain the status of both of the parent dogs prior to breeding, in order to ensure that their subsequent litter are healthy. For potential buyers of Briard puppies too, it is important to find out the status of the parent dogs, in order to understand the status of the pup, both in terms of their own future health and their own potential viability for breeding.

Testing simply involves taking a DNA sample from the dog (often by means of a simple cheek swab) and sending it off to one of The Kennel Club’s approved laboratories, who will then return to you the results of your dog’s status.