There is no doubt that Polycystic Kidney Disease (PKD) has caused a great deal of concern over the last two years amongst cat breeders in Australia, especially in Persian programmes. Certainly, research shows that it is a world-wide issue, has probably been around for two or three decades and may well be found in many more breeds than Persians. This is shown as increasingly so. However, as a Persian breeder above all else, that is where my own concern chiefly lies.

The good thing about PKD is that there is a clear test (scanning at 7.5 - 10 mhz seems to give the most reliable results) for it, so we can find out whether our cats are positive or negative for it. A negative scan is the aim, especially as inheritance of the disease is through a pair of dominant/recessive genes. As in all such pairs, cats which are positive (dominant) can have either one or two positive genes. Those with two such genes will pass a positive gene to all their offspring, while those with only one positive gene will pass it on to only half their offspring on average. Most cats seems to have one positive gene and experience suggests that these cats generally have only very small cysts when scanned.

On the other hand, a cat with a negative result has two negative (recessive) genes and will pass on ONLY negative genes to its offspring.

A mating between a single positive-gene cat and a negative cat can produce all positive offspring, all negative offspring or some of each. The average should be half of each, though we know that the reality in any one litter varies greatly from the average most of the time.

HOW TO REACT:

There are several ways to respond when one finds there are PKD positive cats in the cattery: -

a. Euthanase all positive cats.
b. Desex all positive cats and possibly find homes for them.
c. Breed with only negative cats.
d. Breed between positive and negative cats, trying to eliminate the condition from one's lines.
e. Breed on regardless of whether cats are positive or not.
f. Have cats scanned positive rescanned in case the result was not correct.

In 1998 and earlier in 1999, a number of breeders reacted strongly to the news that they had positive cats, adopting a combination of the first two responses. This left them in many cases with a lot fewer cats. Unfortunately, where one does this, the likelihood also is that one's gene pool and number of breeding lines has also been decreased markedly. Unless new lines can be obtained, the likely outcome is closer breeding of cats. Vets will tell us that inbreeding is likely to cause a number of other conditions to emerge that might otherwise never have surfaced and which could be much more of a concern than PKD, as in almost all cases PKD has so far not killed cats and normally does not affect them in any observable way.

Breeding only with negative cats from the outset is far too limiting, though it would eliminate PKD instantly from one's cattery.

A less dramatic response is to breed between positive and negative cats (along with breeding negative to negative where possible), trying to eliminate the condition by producing negative offspring to continue the lines and, hopefully, the other qualities one is hoping to strive for in the breed. The benefit of this approach is that the gene pool and number of breeding lines does not decrease much, though it may do if the negative offspring produced do not have the desired type or colour, etc. After an initial cooling-off period of a year or two, in which breeders have had time to think through the problem and its implications, this is the approach many breeders have chosen, including ourselves.

Breeding on without testing our cats or without taking any notice of the outcome seems somewhat irresponsible, though of course this is the individual breeder's choice. Given that few cats have died from PKD (mostly kittens and probably where they inherited two positive genes or a particularly bad juvenile version of the disease), it is still an option.

Whichever approach is taken, there is a degree of legal and moral duty involved. When selling cats, especially for breeding, we first need to know if our cats are positive or negative. We then ought to advise the prospective buyer, asking if the condition concerns them and if they want to buy a negative cat. Some breeders, especially in some parts of the world, either don't care or don't want to know. There is argument for selling these people positive cats as long as they have been advised about PKD and have been given the choice. We need to remember that in many countries, and even in some parts of Australia, scanning is not available. Selling kittens for pets has the same ethical questions to consider. Certainly, pet kittens kept until scannable age have lost most of their appeal for the public in general.

Clearly, the number of cats which can be sold that are shown to be negative is only a part of the number of cats produced, so they are at a premium. When so many kittens either have to be euthanased or sold as pets that would previously not have been, the argument that they should be a little more expensive to compensate the breeder for the other losses has at least some validity, though it is certainly not being recommended that negative kittens should automatically be twice the price they used to be.

The good thing that has come out of PKD in Persians is that breeders have bonded together better than in the past and have become more concerned to help fellow breeders who have had a particularly bad set of test results. Some catteries are known to have scanned positive for all cats. Others have scanned mostly negative, though later tests showed that one or two of these were scanned at only 5 mHz and actually were positive when rescanned at greater strength. Unfortunately, definite results from scanning are not generally possible before kittens are at least five months of age; some vets advocating up to ten months or more; the problem being that while it is believed that kittens are born with all the cysts they are going to have, the cysts can be so small they cannot be identified until the animal has grown somewhat. This places extra strain on breeders, as they need to run their stock on for much longer than they would have in the past; thereby adding considerably to breeding costs.

One hopes that the issue will become less important as more cats that are shown to be negative are produced and become available for breeders. In some overseas countries, breeders have decided the whole issue is a storm in a teacup. The most recent information from the USA suggests that many breeders in that country have now chosen to ignore the condition, though this is not necessarily recommended here. In other countries, there is no scanning procedure available, so breeders there either generally don't want to know about PKD or perhaps are forced into decisions based on lack of technology.

In June this year, a further variable has been introduced into the equation. At least one breeder had had a cat scanned positive initially, then because of the inherent value of the cat decided to have it rescanned elsewhere. The second scanning, at our most reliable scanning facility, produced a negative result. Fortunately, the cat is still entire, so it has a potential breeding future. The same breeder now has other stock which will be rescanned in case the same outcome is possible.

What needs to be asked is if other breeders have had the same initial experience having cats scanned and have followed by desexing or euthanasing cats shown as positive in this first test. It seems possible that the breeding programmes of whole catteries could have been needlessly curtailed by such a chain of events. As a result, breeders are advised to ensure their cats are tested at the correct mhz rating, by a competent radiologist, and to be very certain about the status of the results they receive before making irreversible decisions.

Let's hope that we have all made the right decisions, that the quality and future of Persians doesn't suffer too much in the meantime and that DNA/blood testing (which will be possible at a much earlier age) becomes available even sooner than expected.

Rod U'Ren,
Lavendel, Firnbank, Sublime and Preview Catteries,
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