Risk test (DNA based) - Pug Dog Encephalitis

Details about the disease

PDE is an inflammatory brain disease that is usually progressive and fatal.

Clinical signs

Signs of PDE can include seizures, not walking correctly and blindness.

How is it inherited?

The disease is believed to be an autosomal-recessive condition. This means that dogs that inherit two copies of a PDE gene mutation (one from its mother and one from its father) will have an increased risk of developing the condition.

This disease is not fully understood and it is believed that environmental factors or other genetic influences can also contribute to whether a dog becomes affected.

About this test

Since other factors can influence whether a dog becomes affected by this condition, unlike most other DNA tests, this test evaluates a dog’s risk of developing the disease, rather than giving a definitive result.

Current research suggests that 12.5% of dogs that have two copies of the PDE gene variant will develop PDE.

Which laboratories we record and publish the results from?

To find out which laboratories The Kennel Club is able to record results from, and which laboratories will send results directly to The Kennel Club, please refer to our website.

Please be aware, The Kennel Club has a set of criteria that we request DNA testing laboratories to meet to enable us to record their results, helping to maintain and protect the integrity of results that appear on a dog’s record. We strongly advise that customers ensure their chosen laboratory is included on our list if they wish The Kennel Club to record and publish the results. Results from laboratories not included on this list will not be recorded.

How we record your results

Tested dogs will be recorded on The Kennel Club's systems as at “minimal risk (0)”, “minimal risk (1)” or “increased risk (2)”. The numbers assigned to each status indicate the number of copies of the PDE gene variant a dog has.

  • Minimal risk (0) - these dogs do not have any copies of the PDE gene variant and are at minimal risk of developing the condition
  • Minimal risk (1) - these dogs have one copy of the PDE gene variant, but are at minimal risk of developing the condition and may pass either one copy of the normal gene, or one copy of the abnormal gene on to future puppies
  • Increased risk (2) - these dogs have two copies of the PDE gene variant and have an increased risk of developing PDE. However, of these dogs, it is estimated that only 1 in 8 will ever become affected by the condition itself

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 The Kennel Club's official 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.

If your dog is minimal risk (0)

These dogs can be mated to any dogs without increasing the risk of the puppies developing PDE. Your chosen mate should always be tested and your decision should be informed by their results.

Minimal risk (0) x Minimal risk (0)

Each puppy born has a:

  • 100% chance of having a minimal risk (0) status
  • 0% chance of having a minimal risk (1) status 
  • 0% chance of having an increased risk (2) status

This means that each puppy born will have the lowest chance of developing PDE and will not carry a copy of the PDE risk gene variant tested for.

Minimal risk (0) x Minimal risk (1)

Each puppy born has a:

  • 50% chance of having a minimal risk (0) status
  • 50% chance of having a minimal risk (1) status
  • 0% chance of having an increased risk (2) status 

This means that each puppy born will have the lowest chance of developing PDE, but will have a 50% chance of carrying a copy of the PDE risk gene variant. Dogs that are born minimal risk (1) could pass this gene variant on to any possible future puppies.

Minimal risk (0) x increased risk (2)

Each puppy born has a:

  • 0% chance of having a minimal risk (0) status
  • 100% chance of having a minimal risk (1) status
  • 0% chance of having an increased risk (2) status 

This means that each puppy born will have the lowest chance of developing PDE, but will carry a copy of the PDE risk gene variant and could pass this gene variant on to any possible future puppies they have.

If your dog is minimal risk (1)

These dogs can be used for mating, but your chosen mate should always be tested and your decision should be informed by their results.

Minimal risk (1) x minimal risk (0)

Each puppy born has a:

  • 50% chance of having a minimal risk (0) status
  • 50% chance of having a minimal risk (1) status 
  • 0% chance of having an increased risk (2) status

This means that each puppy born will have the lowest chance of developing PDE and a 50% chance of carrying a copy of the PDE risk gene variant. Dogs that are born minimal risk (1) could pass this gene variant on to any possible future puppies,

Minimal risk (1) x minimal risk (1)

Each puppy born has a:

  • 25% chance of having a minimal risk (0) status
  • 50% chance of having a minimal risk (1)
  • 25% chance of having an increased risk (2) status 

This means that each puppy born has a 25% chance of possibly being affected by PDE.

Each puppy will also have a 75% chance of carrying at least one copy of the PDE risk gene variant. Dogs that are minimal risk (1) could pass this gene variant on to any possible future puppies, while dogs that are increased risk (2) will pass this gene variant on to any future puppies

Minimal risk (1) x increased risk (2)

Each puppy born has a:

  • 0% chance of having a minimal risk (0) status
  • 50% chance of having a minimal risk (1)
  • 50% chance of having an increased risk (2) status 

This means that each puppy born has a 50% chance of possibly being affected by PDE.

Each puppy will also carry at least one copy of the PDE risk gene variant. Dogs that are born minimal risk (1) could pass this gene variant on to any possible future puppies, while dogs that are born increased risk (2) will pass this gene variant on to any future puppies.

If your dog is increased risk (2)

These dogs can be used for mating, but your chosen mate should always be tested and your decision should be informed by their results.

Increased risk (2) x minimal risk (0)

Each puppy born has a:

  • 0% chance of having a minimal risk (0) status
  • 100% chance of having a minimal risk (1) status 
  • 0% chance of having an increased risk (2) status

This means that each puppy born will have the lowest chance of developing PDE, but will carry a copy of the PDE risk gene variant and could pass this gene variant on to any possible future puppies they have.

Increased risk (2) x minimal risk (1)

Each puppy born has a:

  • 0% chance of having a minimal risk (0) status
  • 50% chance of having a minimal risk (1)
  • 50% chance of having an increased risk (2) status 

This means that each puppy born has a 50% chance of possibly being affected by PDE.

Each puppy will carry at least one copy of the PDE risk gene variant. Dogs that are born minimal risk (1) could pass this gene variant on to any possible future puppies, while dogs that are born increased risk (2) will pass this gene variant on to any future puppies.

Increased risk (2) x increased risk (2)

Each puppy born has a:

  • 0% chance of having a minimal risk (0) status
  • 0% chance of having a minimal risk (1)
  • 100% chance of having an increased risk (2) status 

This means that each puppy born has a 100% chance of possibly being affected by PDE.

Each puppy will carry two copies of the PDE risk gene variant and will pass one of these on to any future puppies.

Potentially producing affected puppies

A mating which may produce affected puppies could have a serious impact on their welfare. If this mating 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.

Further breeding information

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 they be at increased risk
  • 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 dogs 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 potential 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

Making balanced breeding decisions

As well as considering the implications of a dog’s DNA test results, there are other equally important factors to consider when deciding whether two dogs should be mated together, such as temperament, genetic diversity, conformation, other available health test results, the general health of the dogs etc. Your breeding decisions should always be well balanced and take into consideration the qualities and compatibility of both the sire and dam that you are considering.