PDP1

Pyruvate Dehydrogenase Phosphatase 1 Deficiency (PDP1) is a condition that affects Clumber Spaniels and Sussex Spaniels and was first identified in Clumber Spaniels during the late 1970’s; however little progress with the condition appears to have been made at that time. A full investigation into the condition was launched when it reappeared in the United States a few years ago, many Clumbers in the USA were screened and the report found that 25% of those dogs were carriers of the condition.

It was felt that the UK Clumber population should be tested to determine the extent of the condition within the breed here; this was made possible when, in 2008, the Kennel Club’s Charitable Trust awarded a grant of £4500 towards 100 free PDP1 tests. The Clumber Spaniel Club is indebted to the Kennel Club Charitable Trust for its support in this testing programme.

The test is available from Laboklin and the sample for the test is gathered by a simple mouth swab. Club members will qualify for a 10% discount, further information on this can be obtained from Carol Page on 01489 589734 or health@clumberspanielclub.org.uk

If both parents have tested clear then all first generation progeny will also be “hereditarily clear”, therefore the status of many of our younger dogs can be determined by the results of their parents. However as this condition has apparently arisen as a mutated gene at some time in the past then it is recommended that all dogs used for breeding should be tested.

PDP1 Results

The following articles have been written by Roe Froman from the USA who is a Clumber owner, practicing Vet and Chair of the Clumber Health Foundation, and they are reproduced here with her kind consent. The first gives a basic description of the condition and the second provides information about breeding guidelines.

Pyruvate Dehydrogenase Phosphatase 1 Deficiency

PDP1 is a genetic deficiency identified in Clumber and Sussex spaniels. The lack of the enzyme leads to a failure of the PDH complex, which is responsible for helping to rid the body of waste products from metabolism. When this complex does not function properly, the dog suffers from extreme exhaustion after very limited exercise. PDP1 deficiency can lead to an early death in affected dogs.

Sometimes the problem is not identified until the litter is starting to be lead trained, as pups often seem to self-limit their activity around the home. Affected individuals will start to stagger, then have extreme difficulty moving after exercise such as going for a walk. Eventually, the dog can recover and walk again, but their tolerance for exercise is very low.

PDP1 deficiency is caused by a genetic misfire. It is a simple autosomal recessive, which means that a dog must have two copies of the defective gene to be affected. Dogs with only one copy are carriers, and while they can produce affected pups if accidentally mated to another carrier, they are not themselves affected in any way. Carriers can lead long and healthy lives, and can be safely bred from when mated to clear dogs. Development of the PDP1 dna test allows thoughtful breeders to test their breeding stock, and to safely use carriers in a careful and responsible breeding program. This will benefit the breed worldwide.

Roe Froman, DVM

DNA Tests Results and You: How To Use PDP1 Test Results in Your Breeding Program

There is obviously still a lot of confusion about how to successfully utilize PDP1 genetic testing results in a breeding program. Hopefully this column will help to answer questions and clear misconceptions about using DNA results to help guide successful breedings.

We are very fortunate to now have a DNA test for PDP1 (Pyruvate Dehydrogenase Phosphatase 1), an enzymatic deficiency which causes extreme exercise intolerance in Clumber spaniels. In order for a dog to be affected by this condition, it *must* carry two copies of the defective gene (one from each parent). This defect has been characterized as a simple autosomal recessive gene. That means, a dog must inherit a defective copy of the gene from *each* of its parents in order to show clinical signs of the disease.

Since it is a simple recessive gene, carriers will by definition not suffer from the disease. Carriers also *cannot produce affected puppies* unless they are mated to another dog who also carries the defective gene. Since affected dogs are highly unlikely to ever be bred from, the only way that the disease condition can be produced is via the breeding of two carrier dogs.

*Important*: A carrier dog can be safely used in your breeding program. This is the beauty of having DNA tests available. They allow us to identify carrier, clear and affected individuals genetically. The practical use of this is as follows:

Clear dogs can be safely bred to any other dog. They cannot pass on the defective gene, as they do not possess it.

Carrier dogs can ALSO safely be bred to CLEAR dogs. Since the clear dog cannot pass on the defective gene, and since the carrier will ever only pass on one chromosome, the worst that can happen is that another carrier may be created. Carriers never suffer from the disease themselves, so this poses no health problems. If the Clumber fancy panics and stops breeding carriers, when our breed has a carrier rate of at least 22% of the breeding population, it will be all too easy to breed ourselves into corners which may lead us to much more serious health concerns for the breed as a whole.

This has occurred in other breeds. Breeders who are so happy to have a test that can tell them about a particular disease begin to breed specifically to cull that disease from a gene pool. Unfortunately, all too often this leads to even worse genetic problems cropping up, by virtue of restricting an already tiny gene pool even further. The goal must be to prevent another affected dog from ever being produced. This is easy: breed clear to clear, or clear to carrier – very safely. Two carriers should never be bred together – as this is the ONLY way that an affected puppy can be produced.

The expected ratio of carriers in a hypothetical litter of four pups with one clear and one carrier parent will be two clear and two carriers. Over time, the incidence of carriers can slowly be decreased throughout the breed – without threatening the genetic diversity we must so strongly try to increase. Knowing the status of our breeding animals makes this a simple exercise in genetics. There is no need to remove carriers from a breeding program, if the breeder is willing and able to utilize dna tests intelligently.

Roe Froman, DVM