Articles Index/Health
Posted 05/03/01

INCIDENCE OF GENETIC DISEASES IN NORFOLKS MUST BE ADDRESSED

As more and more Norfolks are being diagnosed with Mitral Valve Disease and other cardiac problems, it is imperative that all breeders share information about the health histories of their breeding stock.

One of the breeds with a high incidence of early-onset mitral valve endocardiosis is the Cavalier King Charles Spaniel. The CKCSC,USA has developed the following protocol to help screen for the defect:

Have health clinics at specialties. Have board-certified cardiologists check all of the dogs for murmurs, and find out at about what age 50% of your breed is affected.

For instance, if 10% of 1-year-olds have mitral valve murmurs, and 35% of 3-year-olds have murmurs, and 50% of 5-year-olds have murmurs, then five years of age is the crucial number.

Then, encourage all breeders to refrain from breeding any animal that does not have two parents that were heart-clear at age five. If a stud dog's parents got their murmurs at age four, then you don't use him unless he himself is clear when he reaches age five. If the stud dog's parents didn't get their murmurs until age six, then you go ahead and use him.

Obviously, if your "50% affected" age is six, then you use six as the cutoff by which the parents must be clear. You can also encourage breeders to send in their clear certificates to OFA, as OFA lists the age at which the animal was certified by the cardiologist.

Popular Sire Effect

While Norfolks do not appear to be anywhere nearly as highly affected as Cavalier's, it is not too early to be taking aggressive steps to combat the spread of MVD.

Dr. Gerald Bell, in speaking to ANTA last fall and in responding to questions on an interactive internet chat line commented, "The problem with increasing genetic disease, and the perception of decreased genetic diversity in dog breeds, is from the popular sire syndrome. If popular sires carry deleterious recessive genes, then these will be spread into the gene pool through their descendants. This is called the founders effect. I have seen genetic disorders become fixed and increase in frequency in breeds through the founders effect. This is not a problem only for breeds with small gene pools. I have seen it in some of the larger AKC registered breeds." (Visit the Canine Diversity Project on the web for more details. Ed.) "Most of my recommendations on disorders without known modes of inheritance, or without tests for carriers, involve knowledge of affected or carrier dogs in the depth and breadth of the pedigree. ... most people are not talking about the affected dogs they produced. Many don't know about them, because they have not followed up on their puppies."

Not Easy ... But Necessary

"Nobody said this was easy. No one wants to produce affected dogs, or to indiscriminately breed carriers. In every genetic disease control program I have been involved with, the vast majority of owners of affected dogs have been pleased that their breeder is interested in their dog and improving the breed so that other affected dogs are not produced."

Many national clubs have established open registries. Depending on the mindset of the breeders, there are different types of registries, and different levels of openness. More national clubs are having health seminars and screening clinics at their specialties, emphasizing the importance of genetic disease monitoring and control. It used to be thought that such events would scare away potential buyers from a breed. We now know that without talking about the problems, in the long run the breed may not be there for the buyers."

As Dr. Bell said, nobody said this was easy. The NNTC and Genetics Chair Carol Falk have begun asking the right questions. The recent heart survey completed by some NNTC members, and even more ANTA members, is an important first step. But, we must be willing to share information with fellow breeders and puppy buyers. How many of us even ask whether a particular dog's parents are still alive? If they're not, do we ask how old they were at the time of death and what they died of?

It's time to share this information and to be concerned about keeping our breed as free from genetic disease as possible.

Sheila Foran
ANTIC, March, 2001

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