PKD is an inherited kidney disease which has become very common in Persian cats and Exotic Shorthairs. Many cat breeders are aware of the problem and have been taking steps to eradicate the gene defect from their breeding lines.

Up until recently the only practical way to identify the affected cats has been by ultrasound scanning of the kidneys and the Feline Advisory Bureau established a UK PKD Ultrasound Screening Scheme for the disease in 2000. Almost 2300 cats have been scanned in this time with an average positive result of 33 per cent. Now that a gene test is available it is the test of choice for many breeders because the sample can be taken by a local vet and kittens do not have to be 10 months old before a reliable result can be obtained. However, ultrasound scanning remains a good screening test for the disease for breeds where the gene test has not been verified and FAB PKD Ultrasound Screening will continue to be available to breeders who need to use this method.

THE GENE TEST

The gene test is currently available in the UK at:

•  Langford Veterinary Diagnostic Laboratory at Bristol University Veterinary School

The tests can be run on a blood sample, or on a sample of cheek cells (known as a buccal swab) collected by swabbing the cat's mouth.

Cats can be tested at any age, but if pre-weaning kittens are being tested it must be done using a blood sample rather than a cheek swab. This is because nursing kittens will have traces of the queen's DNA in their mouth, and this could cause a false test result. However collection of cheek swabs is significantly less stressful for the cat, or kitten, than collection of a blood sample, so it may be preferable to wait until the kitten is weaned, so that testing can be done using a cheek swab.

How to have your cat tested

1. Download and print the submission form from the Langford Veterinary Diagnostic Laboratory (select 'Downloads' from the lefthand menu and then select 'Polycystic kidney disease (PKD) submission form' under the heading 'For Veterinary Practices').
   You will need one copy of the form for each cat that is to be tested. If you are unable to download the form please contact the FAB office and we will be happy to send you a form (call 0870 7422278).
   
   
2. Complete Section A of the Submission Form
   
   
3. Take your cat(s) to your own veterinary surgeon to be microchipped and sampled (buccal swab or blood sample). Your vet will need to complete and sign the form(s)
   
   
4. Your vet will submit the samples to the laboratory and the results will be faxed and posted to the veterinary practice. Ensure that your vet passes on to you a copy of each Submission Form, as well as a copy of each results form. 
   
   
5. Please also ensure that your vet puts the microchip number on the sample tube. This is crucial if you wish your cat to be included on the FAB Negative Register.
   
   
6. If you wish the test results to be included in the FAB PKD Screening Scheme and any negative results to be included on the FAB PKD Negative Register, you will need to make copies of both the submission form and the results form and submit them to the FAB, at the address below, along with a cheque to cover the administration fee. The current administration fee is £4 per cat, or £3 if two or more cats owned by the same breeder are submitted at the same time.

NB: If you want to go on the PKD Negative Register but wish to use the UC Davis Laboratory in the USA, you will still need to link your cat's microchip number to the sample. To do this, you will need to get your vet to take the swab sample and to note the microchip number on the sample and form and ask the laboratory to write this on the result sheet.

A note of caution: In humans there are at least six different genes that can cause different forms of PKD. It appears that autosomal dominant PKD in Persians and related breeds is all caused by one gene defect, but other forms of PKD caused by a different, unrelated gene mutation may exist.

FAB PKD NEGATIVE REGISTER

The FAB PKD Negative Register is now available to view by clicking here. The register allows breeders and owners to look up negative cats - useful for breeders who have prospective owners asking about the PKD status of parents or kittens and for finding breeding cats.

Cats that have been screened negative for PKD by either ultrasound scanning (the FAB scheme) or by the gene test (with a microchip number on the sample and result), can be listed on the FAB PKD Negative Register.

Anyone who had a cat scanned negative under the old FAB ultrasound screening scheme has been contacted and asked if they want their cat(s) to be included. If you are a breeder and in this position but have not received a letter please get in contact - some people have moved since scanning and we do not have updated addresses for them.

Anyone having their cat gene tested can also go on the Register as long as the swab is taken by a vet and the cat's microchip number confirmed on the sample.

Breeders who wish their gene tested cats to be eligible for inclusion on the FAB PKD Negative Register should follow the proceedures outlined above.

Making use of the results of a genetic test

Screening for PKD allows accurate identification of affected cats so that an informed decision can be taken as to whether or not the cat should be used for future breeding. If the cat is found to be negative then there is no problem, however if the cat is positive a number of other factors may need to be considered. The cat may come from a particularly valuable breeding line or it may be free of some of the other congenital or familial problems which affect Persians cats. A further concern is that by avoiding breeding from all PKD positive Persians there will inevitably be increased in-breeding between the remaining PKD negative cats.

If there are enough good reasons to use a particular affected cat for breeding, enough to outweigh the certainty that it will pass PKD on to a proportion of its offspring, then it may be appropriate to mate that cat to cat known to be free of PKD. On average 50% of the offspring will be affected by PKD, but a number of PKD negative kittens would also be expected and these could then be used as future breeding stock so as to maintain the desired breeding line, although there will remain the moral dilemma of what to do with the PKD positive kittens that have been produced by this mating.