Progressive Retinal Atrophy 3 (PRA3) in Tibetan spaniels

Progressive retinal atrophy is the umbrella name given to a range of different degenerative eye conditions that all lead to slow onset progressive blindness, which is irreversible and total but not painful.

Progressive retinal atrophy is a hereditary health condition that is passed down in breed lines from dogs to their offspring, and that can be found in a wide variety of different dog breeds. The various different forms of progressive retinal atrophy in dogs each affect different parts of the eye and work in slightly different ways, although the end result is the same; however, different forms of the condition tend to be prevalent in different respective dog breeds, and require slightly different testing protocols to identify them, as they are each caused by a different gene mutation.

In this article, we will discuss Progressive retinal atrophy 3 (PRA3), which affects the Tibetan spaniel.

The Kennel Club, in association with the British Veterinary Association record incidences of the condition in various different breed lines, and use this information to collate statistics on the prevalence of the condition, and provide supporting data to dog breeders to allow them to pick the right match for their own breeding pair.

Tibetan spaniels that are intended to be used for breeding should be tested for the condition prior to going ahead, and below, we will look at the condition in more detail, how the heredity of progressive retinal atrophy 3 works, and how to get your own dog tested. Read on to learn more.

More about progressive retinal atrophy 3 in dogs

Progressive retinal atrophy 3 is a hereditary health condition that causes around 66% of all cases of progressive retinal atrophy in the Tibetan spaniel breed.

The condition affects the rods and cones of the eyes, which are the parts responsible for receiving light and colour and transmitting information about what the dog is seeing to the brain, where it is formed into the picture that makes up the dog’s vision. When these rods and cones are dysfunctional, damaged or incomplete, the affected dog’s vision will be affected.

Progressive retinal atrophy 3 in dogs leads to progressive damage to the rods and cones, which ultimately results in the dog losing their vision. Whilst not painful, this is naturally very debilitating, and can have a significant impact upon the dog’s quality of life.

What sort of dogs can be affected by the condition?

The PRA3 variant of progressive retinal atrophy is found in the Tibetan spaniel dog breed, but can of course also be identified in hybrid dogs breeds and cross breeds that have some Tibetan spaniel ancestry. It tends to be late in onset compared to other types of progressive retinal atrophy, and generally will not become noticeable or symptomatic in affected dogs until they reach the age of four or more, and generally, the earliest signs can only be identified by a veterinary ophthalmologist.

Around 25% of all Tibetan spaniels in the UK are estimated to be carriers of the condition, and around 3% of dogs of the breed are affected by the condition.

How does the heredity of the condition work?

Progressive retinal atrophy 3 is an autosomal recessive condition, which means that dogs need to inherit two copies of the faulty gene (one from each parent dog) in order to develop the condition.

Different combinations of status in the parent dogs (referred to as clear, carrier or affected) lead to different results in the puppies, which can be summed up in simple terms as follows:

• If both parent dogs are clear, their offspring will be clear too.
• If both parent dogs are affected, their offspring will be affected too.
• If both parents are carriers, the litter will have odds of 50% carrier, 25% affected and 25% clear.
• A clear dog mated with an affected dog will produce offspring that are carriers.
• A carrier mated with an affected dog results in odds of 50:50 carrier and affected in the puppies.

How to get your dog tested for PRA3

In order to have your Tibetan spaniel tested for the condition, you will need to ask your vet to take a DNA sample from your dog, in the form of a cheek swab. This can then be sent off to one of The Kennel Club’s approved laboratories for testing, and they will return the result of your dog’s status to you.

Because the condition is carried by around a quarter of all Tibetan spaniels, breeding only clear dogs results in the risk of the gene pool of the breed becoming so small that other hereditary health issues are apt to come to prevalence too.

This means that a carrier test result does not mean that the dog should not necessarily be bred from-simply that the status of their match must be chosen carefully in order to ensure that the puppies do not develop the condition.