Linkage test (DNA based) - CA (Cerebellar ataxia)

Please note that this is a linkage test - find out what this means below.

Details about the disease

CA is a neurological disorder which affects gait, co-ordination and balance. The cerebellum is the part of the brain that regulates the control and coordination of movement. In this condition, cells in the cerebellum (the part of the brain that controls coordination of movement) begin to deteriorate, causing poor coordination and lack of balance.

Clinical signs

Clinical effects have an early onset and usually present within the first few weeks or months of life. The disease is progressive and affected puppies are often euthanised before the age of 1.

How is it inherited?

The disease is described as an autosomal-recessive condition. This means that a dog must inherit two copies of an abnormal gene (one from its mother and one from its father) before its health is affected. A dog that inherits only one copy of the abnormal gene (from its mother or its father) will have no signs of the disease, but will be a carrier and may pass the gene on to any offspring.

What is a linkage test?

Most DNA tests identify whether your dog has a specific genetic mutation that causes a disease. Linkage tests do not do this, instead they find parts of unrelated DNA that are almost always inherited with the genetic mutation. Linkage tests may not be as precise as other DNA tests, but they can still be highly accurate. Laboratories will often estimate how accurate their test is. The accuracy of a linkage tests depends on the links between marker DNA and the actual mutation being maintained (i.e. them continuing to be inherited together).

Why do laboratories create linkage tests rather than regular DNA tests?

Laboratories may offer linkage tests for three main reasons:

  1. Sometimes scientists are unable to find the exact gene that causes a disease, but they are able to find sections of DNA that are somehow linked to, and inherited alongside it
  2. It may be technically difficult to find the mutation and it may be easier and cheaper to look at and determine linked markers instead
  3. The test for a particular genetic mutation is patented by a specific laboratory and may not allow others to offer this test, or may ask that they pay to offer it. In these circumstances some laboratories may create a linkage test so that they can offer the test to their clients

Which laboratories test for this condition?

A lists of laboratories that offer CA linkage tests can be found below.

Laboratories that send a copy of your dog's results straight to The Kennel Club, so you don't have to.
Laboratories Contact details
AHT (UK) The AHT closed down on 31 July 2020 and no longer offers this test.
Web:
www.aht.org.uk

Where will your dog's results be published?

DNA test results from these laboratories are sent directly to The Kennel Club and are recorded on to the dog's record in the registration database, and are published:

How we record your results

Tested dogs will be recorded on The Kennel Club's systems as “clear”, “carrier” or “affected”.
  • Clear - these dogs do not have any copies of the abnormal gene associated with the condition that has been tested for. These dogs are highly unlikely to develop this condition and will pass on a normal copy of the gene to their puppies
  • Carrier - these dogs have one copy of the normal gene and one copy of the abnormal gene associated with the condition that has been tested for. These dogs are highly unlikely to develop this condition and may pass either one copy of the normal gene, or one copy of the abnormal gene on to their puppies
  • Affected - these dogs dogs have two copies of the abnormal gene associated with the condition that has been tested for. These dogs will likely be affected by the disorder and will pass on one copy of the abnormal gene on to any future puppies

How to find out if a potential mate has been DNA tested

The Kennel Club’s Health Test Results Finder allows you to find the results of DNA tests carried out as part of official Kennel Club DNA testing schemes for any dog on The Kennel Club’s Breed Register.

Breeding information

Breeding information is available below to provide you with details on all possible breeding outcomes.

Potentially producing affected puppies

Producing affected puppies that will develop the condition you tested for will have a serious impact on their health and welfare. A mating which may produce affected puppies should never knowingly be carried out. If this mating accidentally occurs, it is important to test all of the puppies before they are bred from or are passed on to new homes. Veterinary advice should be sought as to the clinical management of any affected puppies.
Why breed from carriers and affected dogs?

Breeding only from clear dogs can have a significant impact on genetic diversity within a breed, increasing inbreeding and therefore the likelihood of new inherited diseases emerging.

  • With simple autosomal-recessive disorders, a carrier will not be affected by the condition you have tested for, but they could pass on a copy of the faulty gene if they themselves are bred from
  • Only when a dog inherits two copies of a faulty gene (one from its mother and one from its father) will it be affected
  • When used responsibly, carriers are an important part of any breeding plan and should not be overlooked
  • By breeding from carriers, you can keep good, healthy dogs in the breeding population, helping to maintain genetic diversity
  • Ultimately, however, over the course of a few generations it would be beneficial to aim to produce only clear puppies, thereby reducing the frequency of the disease-causing variant of the gene in the breed

Similarly an affected dog could still be used in a breeding programme, but this will very much be dependent on the condition and whether the dog's welfare would be affected by the mating/whelping process. They should only be mated to clear dogs, to ensure no affected puppies are produced.

Are clear dogs 100% clear?
Clear dogs are only known to be clear for the condition that they have been tested for, and may carry other unknown mutations which can be passed on to their offspring - it is almost certain that all individuals carry some versions of genes that if inherited in duplicate would result in disease. If a particular dog has many offspring that go on to breed themselves, these unknown mutations may then increase in frequency in the breed and a new inherited disease could emerge. In other words, no dog is completely risk free, but there are ways a breeder can reduce the risk of known and unknown inherited disease. 
Additional cautions about using carriers or affected dogs

Sticking to these rules will mean that you can still use these dogs for breeding, while maintaining genetic diversity within the breed.

  • Never overuse a carrier or affected dog for mating. If a dog has one or two copies of a known faulty gene it should never be overused for breeding. Overusing these dog’s risks increasing the frequency of the faulty gene within the population, making it more difficult for future generations to breed without increasing the risk of producing affected dogs
  • Do your research. If all breeders decided to use carriers or affected dogs for mating, then there is a possibility that as the frequency of mutant genes increases, then the proportion of 'clear' dogs would decline. You can use carriers and affected, but you always want to make sure you have a big enough supply of clear dogs. You may wish to talk to health representatives at your local breed club who will have access to summary information on the results of dogs that have been DNA tested and can advise you appropriately on the current situation in your breed
  • Any possible carrier puppies that go on to be bred from should be DNA tested prior to mating. If you do decide to produce puppies that are potentially carriers, but are concerned that they may be used by their new owners for breeding, then you may wish to consider placing an endorsement on the puppy, or include a statement in your puppy contract that any puppies used for breeding must be tested prior to mating and if the puppy is a carrier, it must only be mated to a clear dog