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The Ins and Outs of Pedigree Analysis
Popular Sires and Population Genetics
Eliminating Genetic Diseases in Dogs:
A Buyer's Perspective
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Consider the hypothetical case of Old Blue, Malthound extraordinaire. Blue was perfect: Sound, healthy and smart. On week days he retrieved malt balls from dawn to dusk. On weekends he sparkled in malt field and obedience trials as well as conformation shows, where he baited to--you guessed it--malt balls.
Everybody had a good reason to breed to Blue, so everybody did. His descendants trotted in his paw-prints on down through their generations. Blue died full of years and full of honor. But what people didn't know was that Old Blue, good as he was, carried a few bad genes. They didn't affect him, nor the vast majority of his immediate descendants. To complicate the matter further, some of those bad genes were linked to genes for important Malthound traits.
A few Malthounds with problems started showing up. They seemed isolated, so everyone assumed it was "just one of those things." A few declared them "no big deal." Those individuals usually had affected dogs. All in all, folks carried on as usual.
Time passed. More problem dogs turned up. People made a point not to mention the problems to others because everyone knows the stud owner always blames the bitch for the bad tings and takes credit for the good. Stud owners knew it best to keep quiet so as not to borrow trouble. Overall, nobody did anything to get to the bottom of the problems, because if they were really significant, everybody would be talking about it, right?
Years passed. Old Blue had long since moldered in his grave. By now, everyone was having problems, from big ones like cataracts, epilepsy or thyroid disease to less specific things like poor-keepers, lack of mothering ability and short life-span. "Where can I go to get away from this?" breeders wondered. The answer was nowhere.
People became angry. "The responsible parties should be punished!" Breeders who felt their programs might be implicated stonewalled. Some quietly decided to shoot, shovel and shut-up. A few brave souls stood up and admitted their dogs had a problem and were hounded out of the breed.
The war raged on, with owners, breeders and rescue workers flinging accusations at each other. Meanwhile everybody carried on as always. After another decade or two the entire Malthound breed collapsed under the weight of its accumulated genetic debris and went extinct.
This drastic little fable is an exaggeration--but not much of one. Here's similar, though less drastic, example from real life: There once was a Quarter Horse stallion named Impressive. The name fit. He sired many foals who also exhibited his desired traits. But when they and their descendants were bred to each other, those offspring sometimes died. Impressive had been the carrier of a lethal single-gene recessive trait. No one knew it was there until they started in-breeding on him. The situation of a single sire having this kind of drastic genetic effect on a breed became known as the "Impressive Syndrome."
Many species and breeds of domestic animals, including dogs, have suffered "Impressive Syndromes" of their own. But cases like that of Impressive are only the tip of the iceberg. A single-gene recessive becomes obvious in just a few generations. But what about more complex traits?
This is not to say that those popular sires we so admire are bad breeding prospects. Their many excellent traits should be utilized, but even the best of them has genes for negative traits.
The problem is not the popular sires, but how we use them. For a century or more, in-breeding has been the name of the game. (For the purposes of this article, "in-breeding" refers to the breeding of dogs related to each other and therefore includes line-breeding.) By breeding related individuals, a breeder increased his odds of producing dogs homozygous for the traits he wanted. Homozygous individuals are much more likely to produce those traits in the next generation.
When a male exhibits a number of positive traits and then proves his ability to produce those traits he may become a popular sire, one that is used by almost everyone breeding during his lifetime, and maybe beyond, thanks to frozen semen.
Since the offspring and grand-offspring and so on are good, breeders start breeding them to each other. If the results continue to be good, additional back-crosses may be made for generations. Sometimes a sire will be so heavily used that, decades hence, breeders may not even be aware of how closely bred their animals are because the dog no longer appears on their pedigrees.
This is the case in Australian Shepherds. Most show-line Aussies trace back, repeatedly, to one or both of two full brothers: Wildhagen's Dutchman of Flintridge and Fieldmaster of Flintridge. These, products of a program of inbreeding, were quality individuals and top-producing sires. They are largely responsible for the over-all quality and uniformity we see in the breed ring today--a uniformity that did not exist before their birth nearly three decades ago.
Working lines have also seen prominent sires, but performance traits are far more complex, genetically and because of the significant impact of environment. They are therefore harder to fix. Performance breeders will in-breed, but are more likely to stress behavioral traits and general soundness than pedigree and conformational minutiae. The best working sires rarely become as ubiquitous as the best show-line sires.
Not every popular sire becomes so because of his ability to produce quality offspring. Some have won major events or are owned by individuals with a knack for promotion. Such dogs may prove to be wash-outs once their get is old enough to evaluate. But a lot of breeders have been using the animal for the few years it takes to figure that out, the damage may already have been done.
Use of even the best popular sires, by its very nature, limits the frequency of some genes in the breed gene pool while simultaneously increasing the frequency of others. Since sons and grandsons of popular sires tend to become popular sires the trend continues, resulting in further decrease and even extinction of some genes while others become homozygous throughout the breed. Some of these traits will be positive, but not all of them.
The owners of Old Blue, the Malthound in the opening fable, and those who owned his most immediate descendants had no idea what was happening under their noses. They were delighted to have superior studs and even more delighted to breed them to as many good bitches as possible.
Dog breeding and promoting is an expensive proposition. One usually winds up in the hole. But owning a popular sire can change that. The situation looks like a winner for everyone--the stud owner finds his financial burden reduced while breeders far and wide get to partake of his dog's golden genes.
No one breeding dogs wants to produce sick dogs. A small minority are callous and short-sighted enough to shrug genetic problems off as the price you pay to get winners, but even they do their best to avoid letting it come to general attention.
We need a total re-thinking of how we utilize stud animals. No single dog, no matter how superior, should dominate the gene pool of its breed. Owners of such sires should give serious consideration to limiting how often that dog is used, annually, through its lifetime and on into the future, if frozen semen is stored. The stud owner should also look not only at the quality of the bitches being presented, but their pedigrees. How much will the level of inbreeding be increased by a particular mating?
The bitch owner also needs to think twice about popular sires. If you breed to the stud of the moment and everyone else is doing the same, where will you go when it comes time to make an outcross?
Finally, the attitude toward genetic disease itself has to change. It must cease being everyone's dirty little secret. It must cease being a brick with which we bludgeon those with the honesty to admit it happened to them. It must become a topic of open, reasoned discussion so owner of stud and bitch alike can make informed breeding decisions. Unless breeders and owners re-think their long-term goals and how they react to hereditary problems, the situation will only get worse.
by Gary F. Mason, gmason@ileaf.com.
Eliminating Genetic Diseases in Dogs: A Buyer's Perspective
© Copyright 1995 Gary F. Mason. All rights reserved.
Reproduced with permission.
Eliminating Genetic Diseases in Dogs:
A Buyer's Perspective
This paper is the first product of an effort I have undertaken that was prompted by the discovery that our five month old Scottish Terrier suffered from Type III von Willebrand's Disease (vWD). The existence of this genetic bleeding disorder was unknown to us until he suffered a near fatal bleeding episode for no apparent reason. Subsequent treatment and testing revealed that he was affected with vWD.
We were quite naive - as I suspect many people are - when we bought our dog. Both of his parents were AKC registered, which we assumed meant that he was a healthy dog from healthy stock. In fact, prior to discovering his affliction, he too was registered (though we could have registered him even after discovering his malady). We have learned the hard way that "having papers" means very little, if anything, about the genetic health of a purebred dog.
This experience convinced us that dogs, and those who own them, should not have to live under the conditions dictated by genetic diseases. This is
especially true since in the main they could be prevented. Our dog's disease has generated a lot of additional expense and worry which might have been avoided by a properly designed and managed breeding program. It has also become clear to us that prospective buyers should be better educated about the world of dogs before they make an investment that could lead to considerable extra expense, and worse, the heartbreak of losing a beloved friend too early.
This effort has no funding or sponsorship from any organization or other individuals. We neither breed nor show dogs, and have no plans to do so in the future. This is a personal attempt to contribute to the identification of, the development of tests for, and the progress of efforts toward the eradication of genetic diseases in dogs.
This article is intended to be an objective exposition on the subject of genetic diseases in domestic dogs. It is of the utmost importance that the information presented be as neutral as possible so as to encourage all interested parties to engage in productive dialog. No attempt will be made to attach any measure of goodness or acceptability to one view of an issue over another. It is hoped that this approach will enable synergies to be created by joint activity among and between parties interested in improving canine genetic health.
While no one is intentionally being eliminated from the target audience, the specific constituencies being addressed are breeders, breed clubs, dog registration organizations, prospective dog purchasers, researchers, and veterinarians.
The goal of this effort is to provide assistance to any and all concerned parties in hopes of making progress toward the elimination of genetic diseases in dogs, and to generate additional interest in that effort. To that end, it is intended to:
Educate the audience on the subject of genetic diseases in dogs. Present a brief summary of some of the research and other activities currently underway
which are working toward the elimination of genetic diseases in dogs. Suggest some options and approaches which can be examined with regard to their effectiveness in reaching this goal, in both the short term and the long term. Foster open dialog and cooperation among and between all interested parties.
Although primarily terrier breeds are referenced here, this effort is not limited to any specific diseases or breeds. On the contrary, it is intended to encompass the widest range of both. It is hoped that in this way, the largest possible group of people will be induced to participate, and the broadest view of the subject will be developed.
This document is a first step, and proposes to use Type III von Willebrand's Disease in the Scottish Terrier as the example around which to build a framework for further efforts. The current level of knowledge about this disease is extensive, and indicates that this disease, in this breed, presents one of the simplest cases of genetic disease in the dog. Even if this proves to be true, vWD still offers a formidable set of challenges to the community committed to its eradication. But as a relatively simple example, it provides the opportunity to"start small". The framework developed for attacking vWD could be used as the starting point for more elaborate requirements which would be dictated by more complex diseases.
Many diseases in the domestic dog are genetic in origin. Examples are vWD, Collie Eye Anomaly, portosystemic shunt, hemophilia, Scottie Cramp, hip dysplasia, Legg/Calvé Perthes, medial patellar luxation, and craniomandibular osteopathy (CMO) -- the list is very long. So far, over five hundred genetic diseases have been identified in purebred dogs, and over a hundred in mixed breeds. They can affect conformation, health (virtually all systems in the body are subject), and temperament. In Scotties alone there are 36 identified genetic diseases, with similar numbers affecting each of several other terrier breeds.There is a great deal of scientific research being performed on the identification of the specific causes of genetic diseases. Because some of the diseases exhibited by dogs are also evident in humans -- vWD is the most common human inherited blood disease -- some benefit could derive from canine research which would be of use in pursuing the human form of the same, or related, diseases.
"There are no more easy problems." Anonymous
The need for accurate definition of the mode of inheritance - The underlying causes of genetic diseases can be very complex. Efforts are underway to identify and isolate specific genes, and combinations of genes, related to various diseases. But it will probably be a very long time before most have been isolated. The research process is costly and very time consuming.
Variation in the expression of the disease - Genetic diseases which appear to be identical across breeds may in fact be caused by different genetic conditions. For example, vWD is believed to exemplify one mode of inheritance in Scottish Terriers, and another in German Shorthaired Pointers.
The absence of accurate tests - Some genetic characteristics can be determined by observation, but more frequently tests are necessary to identify specific genetic diseases. There are currently two tests for vWD, one more recent (and accurate) than the other. They test for the same constituent in the blood, but use different testing techniques. These tests are based upon measuring the quantity of a specific chemical in the blood, and while the test itself is very good, the results are subject to substantial variation based upon the collection and handling of the test samples. And there can be major variations in the amount of the chemical present in the animal due to its condition at the time of sample collection. Other genetic diseases depend upon other methods for their diagnosis. These include X-ray, physical manipulation, and other techniques. Testing for recognized genetic markers, or the genes themselves, will offer a virtually foolproof method for diagnosis. When a definitive test is developed for any disease, there should be no reason to ever produce a puppy adversely affected by that disease.
Any attempt to address the genetic disease problem in dogs must take into account the human component. People breed dogs for many reasons. While there are exceptions to every rule, most breeders of pedigreed dogs do seem to have the animals' best interests at heart. In the main, the production of dogs with genetic diseases today is not done out of malice, but out of ignorance due to a of lack of historical genetic information.
But there are other forces at work as well. Many dogs are shown at events sanctioned by various registration groups. Breeders of winning dogs earn the respect of their peers and others, and that respect can lead to enhanced benefits to the breeders. Within this environment, other benefits can also be accrued from breeding winning dogs. These include improving the breed; gaining personal satisfaction; and commanding higher prices for puppies bred from the winner's bloodlines.
For genetic diseases to be eliminated, they should be given at least as much weight as the other factors considered when breeding a dog -- principally conformation and behavioral traits. For any plan to be successful would probably require that these benefits remain achievable at current rates or better. The incentives provided for the breeding of dogs without genetic diseases should be at least as good -- probably better -- than exist today.
Since genetic diseases are passed to subsequent generations by parents who contribute the causal factors contained within their own genetic makeup, one point regarding this problem is fundamental:
The elimination of genetic diseases can only be accomplished through selective breeding
The problems lie in determining how to identify the diseases' causal factors in dogs; in understanding when not to breed them; and in the implementation of selective breeding programs based upon these factors. Some of the avenues to be investigated include:
First and foremost in solving any problem is ensuring that everyone involved understands it. While genetics can be a very complex technical subject, the basic information required to make progress toward the elimination of genetic disease by developing an effective breeding program is within the reach and understanding of everyone concerned.
Breeders should understand the implications of genetic diseases recognized as affecting their breeds, and take steps to breed only those dogs that will minimize the propagation of unwanted characteristics.
Prospective buyers should be made aware of the genetic diseases related to the breed they are considering. And they should learn to ask that test results or genetic histories for the animals they are planning to purchase be explained to them.
Veterinarians should be able to recognize genetic diseases, and inform owners, breeders, and prospective breeders of their presence in dogs they examine and treat.
A general information publication on genetic diseases in all dogs could be prepared. A cooperative effort among many breed clubs and other interested organizations could reduce cost and gain maximum exposure for such a product. By crossing many breeds, a single publication could be offered to the public at many venues, including shows for single and multiple breeds, county and state fairs, and other events at which those interested in dogs might be expected to attend. There are many opportunities to spread the word.
Dog breeders should have access to at least the phenotypic history of dogs in the lines that produced the prospective mates. Having this information would help breeders to reduce the probability of the occurrence of diseases by enabling them to determine the statistical risks involved for propagating those diseases. The absence of this information means breeding with no possible way of predicting the outcome. It becomes a matter of pure chance.
One way to make this essential information available to breeders is through an open registry, in which genetic diseases are recorded along with the information currently available in the pedigree. Today a stigma is often attached to a breeder and their breeding stock if this information is made known. Rather than sharing the information, this attitude leads to hiding it away. Open registries sponsored by breed clubs could remove this obstacle, and facilitate improved breeding programs. While not perfect, it can certainly help to reduce the problem, and it is within the reach and capabilities of everyone today.
Testing of animals could be required before they are accepted by registration organizations. Ideally, registration would automatically enhance the database of genetic information available for use in breeding programs. Very few registration organizations do this today. Registration of litters could be withheld until test results, histories of the parents, or both were presented to and validated by the organizations. Registration could also carry with it the requirement to monitor the ongoing health of the dog, and to report the appearance of genetic diseases should they occur after registration.
Participation in shows could be made dependent upon test results being furnished to, and being evaluated by, the sponsoring organizations. Once entered, judges could impose penalties on animals that were found to have visible characteristics related to genetic diseases, and forward that information to the appropriate registry.
All breed standards are, in effect, artificial. They have been developed by selectively breeding dogs over the years until they display a certain set of desired characteristics. Sanctioning bodies have procedures by which they can change the standards for various reasons. Physical conformation should be secondary to the health and temperament of an animal. If genetic diseases are associated with conformance characteristics in an inseparable way, breed standards could be modified to eliminate the incentive for breeding to those characteristics once the underlying association has been identified. In England, through a cooperative effort between the UKC and veterinary organizations, standards that created a propensity for disease have been eliminated from all breeds. The Council of Europe has also enacted resolutions that address the elimination of genetic diseases in dogs.
Several organizations throughout the world register purebred dogs. In general, their charters are similar, and they share the common goal of preserving the integrity of purebred dog breeds. There are clubs that sanction various forms of competition, and others that deal solely with medical issues. Some of the oldest, largest, and most familiar include:
The American Kennel Club (AKC) -- Founded in 1884, it is the oldest and most prestigious dog registration organization. The AKC includes in its mission: maintaining and preserving the integrity of a registry for purebred dogs; sanctioning of dog events that promote interest in, and sustain the process of, breeding for type and function of purebred dogs; and taking whatever actions are necessary to protect and assure the continuation of the sport of purebred dogs. These activities are undertaken with the objective of advancing the study, breeding, exhibiting, running, and maintenance of purebred dogs
The United Kennel Club (UKC) -- The UKC was formed in 1898, and today provides an alternative to the more widely known AKC in the United States. It performs many of the same functions: registry, shows, and stud books. The UKC recognizes 212 breeds, including some that the AKC does not. The UKC offers breed, obedience, agility, and hunting trials.
The American Canine Association (ACA) -- A canine registry with a major goal of tracking genetic health. They encourage breeders to perform genetic tests which then appear on their Registration Certificates, and strive to educate consumers to realize that terms "registration" and "champion" do not have the significance that we previously thought they had.
These are some of the organizations working on canine medical issues:
Institute for Genetic Disease Control in Animals (GDC) -- In an open registry such as the one maintained by GDC, owners, breeders, scientists, and veterinarians can trace the genetic history of any particular dog. In order to control the increasing presence of genetic diseases, we must know how prevalent such diseases are in the breed and in any particular dog's bloodlines. The information about each dog automatically becomes linked in the open registry with their relatives. An open registry offers this information for the selection of mates whose bloodlines indicate a reduced risk of producing genetic disease.
The Orthopaedic Foundation for Animals (OFA) -- This organization specializes in examining and rating dogs with specific regard to hip dysplasia.
The Canine Eye Registration Foundation (CERF) -- An organization dealing with canine diseases of the eyes.
Other organizations have embarked upon research and education programs related to health and genetic diseases in specific breeds. Of all AKC registered breed clubs, nearly three quarters have committees to address health concerns in their breeds. Nearly half have a code of ethics that includes health issues. Many breed clubs have either formed or are investigating the formation of tax exempt foundations to pursue health issues within their breeds.
Among the organizations implementing such health related programs are:
The Scottish Terrier Club of America (S.T.C.A.) Health Trust Fund, which was founded in 1994 to detect and investigate health problems; monitor health in Scottish Terriers; participate in research to enhance the prevention of illness; develop and advocate sound breeding practices; foster safe and healthy environments; study and share information that promotes better health in all purebred dogs; and promote and encourage constructive attitudes toward health concerns. In addition, membership in the S.T.C.A. requires that a Code of Ethics be signed which supports the issue of genetic disease elimination in the breed.
The Cairn Terrier Club of America (CTCA). Their Committee for Health Related Concerns surveyed club members in 1987 for the purpose of determining the presence and frequency of genetic diseases in the breed. They have subsequently carried out an intensive education program, engaged the Institute for Genetic Disease Control to provide their open registry, and produced an award winning reference manual on Cairn Terrier genetic diseases.
The West Highland Anomaly Task Council, Inc. (WatcH), which was Formed in the late 1980s for the purpose of understanding and controlling genetic diseases in West Highland White Terriers. WatcH has undertaken programs for education, information sharing, genetic counseling, and research. They have conducted health surveys among the WHWT population, and created a registry to track several genetic anomalies in Westies.
The Jack Russell Terrier Club of America (JRTCA). Unlike other registries which register entire litters at birth, each JRT application for registration is judged on the individual terrier's own merits. Having registered parents does not automatically guarantee that a terrier can be registered. A terrier is not eligible for registration until it reaches one year of age and has attained its adult height, dentition, and other aspects considered necessary for full maturity. Each terrier's application for registration must be accompanied several documents, including a veterinary certificate, a four generation pedigree, a stud service certificate, and color photographs which support the conformation of the dogs to the club standard.
Many projects are underway around the world in the fight against genetic diseases in dogs. The approach taken by organizations varies -- some are doing scientific research while others are providing education. Here is a sampling of some of these groups:
The Dog Genome Project -- The dog genome project is attempting to map the entire genetic makeup of the domestic dog (there is a similar project underway for humans). The result will be a useful tool for the entire scientific community for the purpose of isolating the genes causing inherited diseases. It is a collaborative study involving scientists at the University of California, the University of Oregon, and the Fred Hutchinson Cancer Research Center. The dog genome project makes all research results available to the scientific community electronically on the World-Wide Web prior to traditional publication.
Project TEACH of the Pet Health Initiative -- Project TEACH (Training and Education in Animal Care and Health) was formed to educate about proper animal care and methods of genetic screening. Project TEACH is an accreditation program for individuals. All TEACH-accredited breeders, pet shops, rescue organizations and humane societies will screen animals for potential problems before they are sold.
AKC Canine Health Foundation -- Established by the AKC in 1995 with a million dollar endowment. The Foundation is intended to raise money to support health research which will benefit dogs, and will identify areas for research and seek qualified individuals to do the research through its Scientific Advisory committee, concerned fanciers, the Delegate Committee on Health Research and Health Education, and others. Since the early 1980's, AKC has been a major funder of genetic research to benefit dogs. The AKC was the principal funder of the work of Dr. Donald Patterson at the University of Pennsylvania to develop the Canine Genetic Disease Information System, a database for veterinarians.
Better Companion Breeders Association (BCBA) - Formerly the Better Dog Breeders Association (B.D.B.A.). A public service agency devoted to the protection of the buying public. They provide their service free to the public, while providing members with special services to assist them in operating their business.
A concerted effort is required by everyone involved with purebred dogs if genetic diseases are to be eliminated. Science is making progress, but the time and expense required for the research point toward this being a long term solution. In the short term, the situation must be addressed using the tools at hand. Open registries for purebred dogs, administered by their respective breed clubs or independent registry organizations, appear to be the easiest and fastest way to a short term solution. They could also provide valuable corroborative information to genetic disease researchers. Cooperation between dog breeders, researchers, prospective purchasers, and purebred dog organizations at all levels is essential if genetically healthy dogs are to become a reality.
One thing is certain -- without the continued attention of many people, the situation can only get worse.
CREDITS
© Copyright 1995 Gary F. Mason. All rights reserved. However, you are encouraged to copy and distribute this article for non-commercial use with the following restrictions: You may not modify the article in any way. You must include the entire article including the copyright notice. You may not charge any fee for use, copying, nor distribution of the product with the following exceptions: Non-profit organizations may charge a nominal fee (not to exceed $5.00) until and unless notified by the authors this is not the case.
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