Precious purring hearts!
Mark D Kittleson, DVM, PhD, one of the foremost researchers on Hypertrophic Cardiomyopathy (HCM), was asked a series of questions trying to sort out this disease and what it means for breeders. Excerpts:
Q: At what age in males and females can this disease ‘actually’ be diagnosed?
Mark: In Maine Coons, most males have evidence of the disease by two years of age and females by three years of age but we have seen it developed as late as seven years of age in females and have seen it developed as young as six months of age in kittens from mating two affected cats.
Q: Is there scientific proof that this genetic disease is 100 percent NOT diet related?
Mark: In Maine Coons, American Shorthairs and humans, HCM is inherited as an autosomal dominant trait. There has been no evidence of a nutritional cause in any species.
Q: Can two parents ‘test’ negative throughout their lives and still produce some kittens who may have HCM?
Mark: Yes. This means that either one of the parents had whatever mutation but did not manifest the disease or the affected offspring had a mutation developed spontaneously in-utero.
Q: Does the word ‘genetic’ mean the kittens are born with it or just predisposed? As soon as the cat reaches adulthood, should it show at that time, since the organs are fully mature?
Mark: Genetic means there is an abnormality in the genome. This may be the form of one base pair mutation or may take the form of multiple abnormalities. The word for a disease that is present at birth is ‘congenital’. For HCM, for example, in Maine Coons the disease is not present at birth but develops over time and so it is not a congenital disease in the classic sense.
Q. If a cat tests ‘negative’ for a number of years, and then reaches say 10-12 years of age, is there a 100 percent chance that she will never have HCM?
Mark: I suspect that there are a fair number of cats who have mild to moderate HCM all their life and then develop something like hyperthyroidism or high blood pressure when they are older and this exacerbates the HCM to become severe. So, it’s theoretically possible to have a cat with mild disease (which would be difficult to detect on an echocardiogram) that developed hyperthyroidism when she was 15 years of age and all of a sudden showed up with what appears to be severe HCM.
Q. Is this an all breed cat condition in general or is it more towards specific breeds of cats?
Mark: It’s a strange phenomenon. HCM is very common in cats, whether they are mixed breed or purebred, yet it’s a rare condition in dogs. And it seems as things progress, more and more purebreds are recognised as having the disease. However, the disease is still most commonly seen in mixed breed cats. If the disease is inherited as an autosomal dominant trait in all cats it would be passed on to 50 percent of all offspring, whether they were purebred or mixed so she would be easy to disseminate a mutation throughout a large population.
Q. Is this condition a game of Russian Roulette?
Mark: You’re correct, echocardiographic screening is a bit of a game of Russian Roulette. If not all cats with a mutation manifest the disease, then it isn’t seen in all cats on an echocardiogram that can pass on the disease. That’s why I always tell people that echocardiographic screening is not going to rid a breed of the disease.
HCM can be treated if diagnosed early. There are various medications available to extend the life of our cats. It would be a much better solution to not breed cats who are HCM positive to begin with. To avoid HCM, breeders should note the following:
- A breeding male should be tested every six months if at all possible. Testing should begin when the male is about one year of age and before he is used in a breeding programme.
- A breeding female should be tested prior to each breeding or at least annually. As with a male, the first testing should be done when the cat is about one year old.
- All breeding cats should be tested as long as they are in a breeding programme.
- An affected cat should immediately be removed from a breeding programme, altered (unless clinically contraindicated), and treatment started as ordered by the breeder’s veterinary specialist.
- Should HCM be diagnosed in a cat, the breeder of that cat should inform *all* pet parents of near relatives of that cat, including offspring of the affected cat, whether they were sold for pet or breeding purposes.
- Breeders are encouraged to maintain contact at least annually with the pet parents of all cats produced by their cattery. Such continued contact should include a report of any health changes in these cats. This information will assist the breeder when making decisions regarding his/her breeding programme.
- Breeders should make every effort to work with breeding cats who are as free as possible of this disease. Furthermore, it encourages breeders of cats to stress the importance of health for their breeding cats as well as type when breeding animals are selected and mating decisions are made.
- It is recommended that breeders include a warranty statement in their sales contract so both parties are informed of what will be expected should the cat or kitten develop HCM.
(Cánie V Brooks is a TICA All Breed Judge. Breeding and showing Bengals for 14 years, she is currently on the TICA Bengal Breed Committee, TICA Mentoring Committee, Past Officer for seven years in The International Bengal Cat Society.)