Feline Health - PKD

Introduction

Feline Polycystic kidney diseased (PKD) is an inherited kidney disease found in cats. There is evidence that Persian and Exotic cats may be more effected than most. PKD has been reported sporadically since 1967 but studies were not conducted until 1990. Most of the work in the USA was conducted by D Biller, S DiBartola and W Lagerwerf.

What is PKD

PKD is a disease that shows up at any time in life and can cause enlarged kidneys and kidney dysfunction occurring between one and 10 years of age. The disease is inherited and cysts are present from birth but may be very small on young animals. Cysts can vary in size from below 1mm to 10mm. The number of cysts varies and one or both kidneys may be affected. Problems occur when the cysts grow and reduce the kidneys ability to function properly. Failure may be the ultimate result. Most of the original work was conducted with Persians and Exotics and sadly it has been found to be fairly widespread. However it is not limited to these breeds and the disease has been seen in many breeds including household pets with no pedigree cat associations at all. The present FAB data reflects this view but is biased as few other breeds are yet testing (and maybe pretending that it will go away on its own – it won’t!)

Diagnosis

Up until fairly recently, ultrasound has been the only technology to detect to the cysts on the kidney. Ultra sound is a fairly simple method especially with today’s good quality equipment. This is a non-invasive technique and providing the equipment is adequate, ensures a high success rate in identifying the condition. Biller et al, indicate that ultrasound diagnosis is 98% accurate when involving cats over 10 months of age. One of the participating FAB scheme organisations with superb imaging equipment and staff, is the Animal Health Trust at Kentford near Newmarket. Generally cats do not required sedation and many ultrasound operators do not clip the coat.

The good news

However there is even better way now. The gene causing the problem is thought to be a single gene and has been identified. A dna screening protocol has been established at the Veterinary Genetics Laboratory, which is part of the University of California in Davis, CA. Even better still, the methods have been verified and adopted at the Langford Veterinary Diagnostic Laboratory at Bristol Veterinary School. There are likely to be others in the UK who will also offer the dna test. Bristol has worked with FAB to make this testing method as easy for owners, breeders and Vets. Cats may be tested virtually at any time; kittens should be fully weaned to exclude traces of the mothers dna. Samples are taken by collecting cells from the inside of the cat’s mouth on sterile swabs. Blood samples can be used but the mouth swabs (technical term: buccal swab) are so easy, painless and convenient that really there is no choice. For FAB recognition, the swabs should be taken by a Vet and the cat uniquely identified by its microchip. The Vet sends the samples off to Bristol and the result comes back in a week or so. The dna method of diagnosis is much more precise that the scanning method and considerably less stressful for the cat. Exotic Cat Club Members can apply for discounts for genetic testing carried out by Langford Veterinary Services in Bristol. A prices list is shown here. Follow this link for more details. The Breed Society Promotional Code can be obtained by emailing the Club Secretary. FAB are establishing a PKD Negative Register and building up statistics on the occurrences.

Ultrascan of a normal kidney

Ultrascan of a normal kidney

Ultrascan showing a cyst

Ultrascan of a kidney showing a cyst

How are cats effected?

PKD is NOT contagious. Studies indicate that it is an autosomal dominant inherited disease. As such the disease will show if one gene is present. This can be derived from either the mother or father or both parents. Thus if one parent shows the disease and the other does not, there is 50% probability that the progeny will carry the gene and thus show the disease. A limitation of the scanning technique is that where as a cat can be identified as positive, it may not be possible to guarantee a cat is negative! It can really only be said that cysts were not detected as they may develop later in life. The advantage of the dna test is that the test gives a much more reliable result. A form of PKD is also seen in humans and here it is thought that there may be more than one gene as the cause. We shall just have to wait and see if the cat PKD dna test totally eliminates this disease, but without doubt it will have a very significant benefit to the breed.

What is the treatment?

There is no treatment for this disease. However recognise that the cat live a long and happy life and the effects of PKD may not effect the cats lifestyle. But clearly PKD does effect some and may shorten life.

Can PKD be eliminated?

As PKD is the result of an autosomal dominant gene, the disease may be eliminated. The quickest way to eliminate the presence of the disease is to neuter and spay all individuals that are indicated to have the disease. Then if breeding programmes only use cats that have been tested negative, the problem can be totally resolved in ONE generation. However when the gene pool is small or breeding cats have especially valuable qualities, they could be used as some of the progeny will not inherit the disease but some will. Subsequent testing sorts out those who inherited the disease and those that did not. It is a personal decision whether this is ethical or worthwhile.

Conclusion

MOST IMPORTANT - It is nobody's fault. This disease has been around to at least 30 years and probably a lot more. It is now understood a little better. Cats are dying in significant numbers at a young age due to this disease. But it can be eliminated by careful investigation and selection and the cat world must be a better place – isn’t it?

ALWAYS seek the advise of your veterinarian