PK Deficiency from a Breeder’s Perspective
Kendall Smith, Kenipurr Cattery
Let me tell you about Brandy, which is why I am here tonight. Brandy was 20 months old, and I was showing her toward a Regional win. In the fall of 1998, she began cycling heavily. By December, she was losing weight so I planned to breed her after Christmas. While I was away, my American Shorthair male got loose and bred two of my Aby girls, Brandy included. In January, she was still losing weight and began vomiting. A vet exam turned up the pregnancy and severe anemia. My vet was convinced she was bleeding out somewhere. As there was no apparent injury, he suggested a bone marrow biopsy. That result came back as “normal, regenerative cells.” Her FeLV test was negative. Next he suggested a special fecal test which was negative for blood in the intestines. I had her spayed, hoping that hormones were playing a role in her anemia, but still she went downhill. At that point, my vet held a phone conference with two veterinary clinical pathologists. They told him Brandy had “some aspect of AIHA, but not AIHA.” We didn’t know what else we could do, and she continued her cycle of vomiting and losing weight, then no vomiting and gaining back weight. Soon after, both Kim Ghobrial and Erin with SABRE posted the information about PK anemia testing to the Aby list. The words, “cyclical anemia” jumped out at me. I tested Brandy, and her results showed her to be affected. She has two mutant genes. Privately, from some of you wonderful people, I learned about the experimental splenectomy surgery. My vet was willing, and on Aug. 24, weighing 4.9 pounds, Brandy had her surgery. On Sept. 29, just 36 days later, she weighed 7 pounds. She has returned to the show ring that she loves, and is just 2 points shy of granding as an alter
Through a friend, I discovered that Dr. Lothrop, one of the leading experts in erythrocyte metabolism involved in PK deficiency, was at the Scott-Ritchey Research Center where his focus is on dogs. He said that Dr. Giger discovered the normal sequence and mutation for PK in cats and was the best source of information. Since Dr. Giger has not yet published his findings (although I do have his rough draft if anyone wishes to read it), for the time being, he is the only one able to provide this DNA test. Molecular diagnosis is THE way to do carrier screening. In response to my question of what do I say to the unconvinced, Dr. Giger said, “As we have experienced with other hereditary diseases, the breeders and pet owners are somewhat hesitant to accept a new hereditary disease in their breed. DNA testing is one of the most accurate tests available as it looks specifically for the mutated gene in an animal. Most certainly, we have no plans to provide a test that is not useful. Developing this test and running this test is considerably more expensive than what we are presently charging.” I actually told him that I REALLY want to believe in a faraway lab with unknown people performing a test I’ve never seen. The cost of the test itself is $75. Add to that a blood draw fee and shipping. I use overnight FedEx so that I can track the package. It costs me about $20 for shipping and amounts to about $100 per cat.
Have any of you lost an Aby with a diagnosis of “anemia of some sort,” “a fluke anemia,” “probably Hemobartenella,” or “some aspect of Autoimmune Hemolytic Anemia”? Have you heard others talk about the anemia that “follows dilute lines”? Think about this; PK is a recessive gene. When you breed for dilutes, you are breeding for a recessive gene. Of course if the PK mutation is there, you’re going to see it quicker! If my line-chasing is accurate, it’s out there almost everywhere, but because it’s a recessive, many breeders seldom see it. Or it was a pet with an owner who never notified the breeder. Or it was a breeding cat with an owner who didn’t want to notify the breeder. Or it was a cat misdiagnosed with hemolytic anemia. Or it was a breeder/owner who doesn’t want to admit it.
This is a simple recessive, easily removed from the gene pool through DNA testing. A cat who has PK deficiency has 2 mutant genes, one from each parent. This means that both parents are at the least, carriers. Some males have lived long, healthy, productive lives only to test as affected at 8-12 years of age. Think about the numbers of carrier or affected kittens that male produced before being tested. Females don’t seem to be so lucky. Affected females appear to have trouble with their first litters: aborting, premature delivery, or death of the female.
In order to not lose cats and bloodlines, you breed a known carrier to a known clear cat. Then test any kitten you consider keeping. Keep the clear kitten. You have the genetic components in a non-carrier package. With RA so rampant in our Abys, it is imperative that we use some of the carriers, but only keep clear kittens. Carriers will not become ill with the disease, and when bred to clear cats, no offspring will become ill. If a cat is affected, you alter it. I personally wouldn’t breed a known affected female since everything I’ve heard indicates that she will die soon after the first litter. If it is VERY important to use a male, breed the affected male to a known clear female and keep one of the kittens. Without testing, that kitten will be a carrier. Breed that kitten to known clear cats, and test any of those that you keep.
When I told Dr. Giger about this meeting and asked for information to pass on, he wrote a short “speech” for me to read to you.