Prioritizing Genetic Defects
George A. Padgett, D.V.M.
Michigan State University
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Since all dogs (or nearly all dogs) carry some genes for genetic defects, if you wish to control the defect in an effective manner, it is necessary to prioritize them because most dogs don't carry just one or two abnormal genes; they have 4 or 5 or more. For example, we know Cairn Terriers have about 5.6 and Newfoundlands 4.8 defective genes per dog on the average. We don't have as good information on most breeds of dogs because they have not conducted an effective survey like these two have. Many breeders, breed clubs and apparently the A.K.C. believe that the less you talk about a problem the more likely it is to go away. This is clearly not the case because as you know we have been hiding them for years and none have gone away. It takes effective and continued selection to reduce the prevalence of a gene defect. Take collie eye for example. A group of breeders, with the help of Dr. William Yakley, reduced the prevalence of this disorder by 38% over a 3 year period in the northwest, while in the rest of the U.S. it remains a widespread problem. This same group of breeders reduced the prevalence of gray collie syndrome to negligible levels a couple of years earlier. There are other examples, like the Portuguese Water Dog Club that made major inroads on hip dysplasia and all but eliminated their storage disease problem in a few short years. The Malamute Club of America greatly reduced the prevalence of malamute dwarfism albeit there was some disagreement on what to do with carriers. So it is clear that genetic disease can be controlled, but they cannot be controlled by hiding them. In fact, hiding the defects, rationalizing them, minimizing them, and in some cases flat out lying about them is causing the puppy lemon laws like the one recently passed in Florida to come into being. No sane breeder and no one interested in purebred dogs, like me for instance, wants to see this happen, but folks whether we like it or not, it is happening.
Can we do anything about it? Of course, but not by sitting on our hands, keeping our mouths shut, closing our eyes, and letting our dogs go blind, be crippled, have fits, and other characteristics which make them unfit to be show dogs, hunters, obedience animals, and most important, good pets and companions. Breeders love their dogs (at least most of them do), and the people they sell them to bond with them and they become part of the family. This is what we want to happen with dogs, we love them, they love us and provide great pleasure and satisfaction in our lives. Is it any wonder that people are upset when their dogs go blind or become crippled or develop a disease that may cost 2, 3, or 4 times the original cost of the dog? Not to my mind. I believe they have a right to be upset and the buyers do, too.
It is clearly time for breeders, breed clubs, the A.K.C. and the veterinary profession to come to grips with the problem, both to preserve our integrity and the health and well being of our canine friends.
If 40-50 percent of our dogs have a defect themselves and in addition carry 4 or 5 genes for other deleterious traits, isn't the situation almost impossible to resolve? The answer to that is clearly yes, unless you do something to put order in the picture. We must prioritize the traits and work on those which harm our dogs first and put on the bottom of the list those things which do little harm or which we can readily correct. We have to quit thinking like we did in 1920 and look at the real situation as it is in the 1990's. I hate to tell you this, but all dogs are not perfect, and since that is true, we have to decide what we can live with and what we cannot. Why is it that we can cut the tails and ears off a dog and show it, but can't repair an inguinal hernia and show it? They are both (for the most part) for cosmetic purposes. Who makes rules that requires an inguinal hernia to become equivalent to PRA or cataracts or malamute dwarfism in terms of selection? The A.K.C. needs to reconsider some of their rules and adopt a more sensible and realistic approach to the realities of nature and of dog breeding. However, given that the situation of dog breeding is as it is today, how do you solve the problem?
Step one - Since every time you breed dogs you get whole dogs, not just eyes or hips or elbows or hearts, you should always look at the whole dog first. The whole dog is composed of somewhere between 10,000 and 110,000 genes; we are not sure exactly how many, but it should be obvious that it is easier to control 1 or 2 or even 5 genes than it is to control 100,000. Therefore, you must pick a dog (or dogs) for breeding that will allow you to accomplish your goal(s), be it conformation, hunting, obedience, or the production of good pets. If your goal is to win at conformation, it will do you no good to produce an animal with superb hips if it doesn't win in a 100 times out. You will not be satisfied with the dog even though it is healthy. So you must pick the WHOLE DOG FIRST. Of course, it will be best if you can select 3, 4, or even 5 dogs that fit this category to allow secondary selection parameters to be introduced. However, with a few exceptions, this is not essential, it just makes life easier.
Step two - There are some traits that override the primary selection parameters (i.e., conformation, hunting and working abilities). In my opinion, one of these and perhaps the only one is temperament. It should be obvious to those of us that are involved with purebred dogs that the public (including legislators) is upset about the potential for physical harm that exists with dogs. We need to come to grips with the fact that many people, perhaps most people, cannot handle some of the dogs produced by breeders. They are not familiar with aggressive dogs and do not have the knowledge or skill to handle them. This, of course, causes many problems, hence the specific breed and all breed legislation that has swept the country. But, although the problem may be more severe with some breeds than with others, in reality it applies to all dogs. I have seen massive efforts by the AKC, specific breed clubs, and all breed clubs to modify the proposed legislation to bring it into a more realistic evaluation of and correction of the problem. These meet my hearty approval. However, I have seen little in the way of efforts by any of these organizations to get at the heart of the problem, that is, the dogs themselves. The number of dog bites tends to be proportional to the size of the breed, although perhaps not completely so. There is also a clear variation in the intensity and severity of the attacks. However, it should be obvious that such breeds as Golden and Labrador Retrievers, Collies and Poodles (etc.) bite more people than Bull Terriers. This is not because they are more aggressive, but because there are more of them, lots more. This, of course, applies to all breeds, not just the four mentioned above. WE NEED TO MAKE IT CLEAR IN A STRAIGHTFORWARD AND UNAMBIGUOUS WAY THAT IT IS UNACCEPTABLE TO BREED DOGS WITH A POOR TEMPERMENT We can argue ad nauseam about what poor temperament is, but we cannot accept it in our breeding stock, no matter how good their other characteristics are.
Although I am not a behaviorist (nor do I intend to become one), I offer this opinion realizing that it does not cover all aspects and that there are some extenuating circumstances in some cases. DOGS THAT BITE PEOPLE AND OTHER DOGS, DOGS THAT CONTINUALLY GROWL AND EXHIBIT AGGRESSIVE BEHAVIOR TOWARDS PEOPLE AND OTHER DOGS, DOGS THAT MORE THAN ONCE UPSET OR INTERFERE WITH CONFORMATION SHOWS OR FIELD, OBEDIENCE AND OTHER TRIALS (and the first time should be documented) SHOULD NOT BE BRED INDEPENDENT OF ALL OTHER FACTORS.
The AKC and specific breed clubs, as well as all-breed clubs, should instruct their judges that such behavior is unacceptable in dogs and these dogs must be excused from the ring or trial. It is most important that they be excused on the first offense, because we cannot document the second offense without the first being in place. Those dogs exhibiting poor ring or show behavior twice should be permanently excused. Those judges that cannot or will not excuse dogs for poor behavior should themselves be excused from the ring, permanently.
Over a period of time, if we continually select against poor behavior, and if all of our clubs and judges exert the peer pressure necessary to make this a standard selection parameter against poor behavior, we will again regain trust of our dog buying public.
Step Three - We have now selected our breeding stock, that is a dog (hopefully dogs) that fulfills our good citizen requirement as well as our requirement for a winning phenotype, be it in conformation, hunting, obedience, working, or serving as a good pet and companion.
A good breeder with some experience with dogs in his/her line or kennel should know the diseases that are present in his/her stock. There may be some excuse for a new breeder or one that has produced only 1, 2, or 3 litters not being aware of what his/her stock carries, but there is no excuse for the breeder that sold him/her that stock not telling her/him what disorders are involved with the line. Good breeding practices require ethical behavior. Be that as it may, if you know what's in your stock you know what to select against, which means that what is good and correct for one line may be inappropriate for another. So it should be understood that all breeders will not be facing exactly the same problems at the same time.
Since there are an average of 4 or 5 defective genes per dog and since it is difficult to select against more than one (or perhaps, if you are lucky, two) trait(s) at a time, you need to prioritize the disorders. In table 1, I present my opinion of a prioritization scheme, a hierarchy of disagreeableness of genetic traits. As you look at the table, you will see that a given trait may fall into more than one category. The more categories it fits the less desirable it is so the more severely it should be selected against. This table is not intended to be a list of the only diseases you should select against; they are examples and there are hundreds of other diseases that belong in one or more of the categories. Further, there are no breeds of dogs that are exempt from this table. Just because I have not mentioned a disease that occurs in your breed does not mean that no such disease occurs in your breed. Further, just because you do not have a severe trait in your line or kennel does not mean that you should not select against the less severe traits.
Once you have selected your breeding stock and know what traits occur in your stock and have prioritized them, you now know what to look out for in the mate. It is true that it is difficult to determine what traits will be present in your selected mate because breeders tend to avoid telling you or minimize them or outright lie about them, but you now have a starting point and can ask appropriate questions, which will help you block the occurrence of a trait or eliminate the gene from you line or kennel. Most of the dilemma about identifying dogs which carry genes for specific traits could be eliminated by open registries. An open registry identifies dogs that are affected with or carry specific defects as well as those dogs that are phenotypically and genotypically normal for such traits.
HIERARCHY OF DISAGREEABLENESS OF A GENETIC TRAIT
- DISORDERS THAT CAUSE PAIN TO THE ANIMAL (examples: glaucoma, cranial mandibular osteopathy, hip dysplasia, entropion, portocaval shunts, dermatomyositis, cancer)
- DISORDERS THAT DISFIGURE, MAIM OR OTHERWISE RENDER AN ANIMAL NONFUNCTIONAL (examples: English Pointer dwarfism, cataracts, retinal dysplasia and detachment, Malamute chondrodystrophy, PRA, deafness)
- DISORDERS THAT KILL (examples: malignant histiocytosis, inherited kidney disease, Anasarca, globoid cell leukodystrophy, osteosarcoma, Portuguese Water Dog storage disease)
- DISORDERS THAT REQIRE TREATMENT FOR THE LIFE OF THE ANIMAL (examples: Grey Collie syndrome, diabetes, epilepsy, copper toxicosis)
- DISORDERS THAT REQUIRE SURGICAL CORRECTTION FOR THE ANIMAL TO SURVIVE OR LIVE A RELATIVELY PAINLESS LIFE (examples: esophageal achalasia, ventricular septal defects, elbow dysplasia, distichiasis)
- DISORDERS THAT ARE DIFFICULT TO CONTROL (examples: multigene traits, late onset traits such as sebaceous adenitis, subaortic stenosis, osteochondritis dissecans)
- DISORDERS THAT ARE READILY TREATABLE AND RESPOND WELL TO THERAPY (example: hypothyroidism)
- DISORDERS THAT REQUIRE ONE TIME SURGERY THAT IS HIGHLY SUCCESSFUL AND PRINCIPALLY COSMETIC (examples: inguinal hernia, umbilical hernia, mild tooth disalignment - these are equivalent to tail docks and ear clips, unilateral cryptorchidism)
- DISORDERS THAT PREVENT AN ANIMAL'S USE FOR THE PURPOSE FOR WHICH IT WAS BRED (examples: Samoyed albinism, correct color, mild bite, dentition and gait abnormalities)