Chondrodysplasia

Historical CHD Information

An overview of chondrodysplasia in the Alaskan Malamute and of the Alaskan Malamute Club of America eradication program

Linda M. Dowdy Originally written May 1981 First update October 1999 Second update October 2004 Chondrodysplasia is a genetically-determined skeletal disorder that occurs primarily in the purebred Alaskan Malamute. The purpose of this article is to describe chondrodysplasia and to outline its relation to the veterinary practitioner.

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Background

For a number of years Alaskan Malamute breeders in both Canada and the United States have been aware of occasional litters which contained deformed or “dwarfed” puppies. But it was not until the early 1970’s that these puppies were conclusively proven to be the manifestation of a genetic disorder. At first these affected dogs were known as “dwarfs” because of their diminutive size. This term however gave rise to considerable confusion with the dwarfism found in Hereford cattle. So another name, chondrodysplasia, was coined and brought into usage. This disorder, however, does involve far more than simply faulty cartilage maturation. Perhaps when it has been fully understood and defined, then a more comprehensive name will be in order.

Inheritability

Chondrodysplasia is transmitted as a simple autosomal recessive trait. Its mode of inheritance was determined by mating all combinations of unaffected, recessive carrier, and affected animals, until a total of one-hundred-fourteen (114) puppies had been produced. Identification of chondrodysplasia as a simple recessive has led to categorization of the Malamute into three distinct genotypes.

Homozygous dominant – clear of the gene (symbol +/+)
Heterozygous – recessive carrier of the gene (symbol +/dan)
Homozygous recessive – chondrodysplastic (symbol dan/dan)

The term “dan” is taken from a concatenation of the words “dwarfism anemia”. d = dwarfism an = anemia

Phenotype

The chondrodysplastic Malamute displays in varying degrees the following phenotypic characteristics.

Excessively shortened front limbs with various degrees of bowing and deformity, especially the radius and ulna
A topline that slopes from the pelvis down to the withers

Some chondrodysplastic Malamutes display a severe degree of deformity while others display almost no visible characteristics. It is important to note that the recessive carrier genotype displays no physical identifying characteristics, being completely normal in appearance.

Radiographic

Chondrodysplastic puppies, up to twelve weeks of age, are readily identifiable by radiographs of the carpal joint. Although all endochondral bones in the chondrodysplastic animal are affected, the condition is most apparent at the distal end of the ulna. In a normal puppy the distal metaphysis of the ulna appears V-shaped and evenly opaque, consistent with normal ossification and development. In the chondrodysplastic puppy, the distal metaphysis of the ulna is distinctly flattened and irregular, with a blunt widening of the distal diaphysis. There is variable evidence of normal ossification. The physis is increased in width with an irregular metaphyseal margin. After twelve weeks of age the joint begins to change. Some adult chondrodysplastics radiographically display relatively normal ossification. Therefore radiographs should not be assumed as a definitive diagnosis after twelve weeks of age. Radiographic evidence is most consistent between five and twelve weeks of age.

It is important to note that the sloping topline of many chondrodysplastic animals is a manifestation of alteration in conformation of the limbs and is not related to changes in the axial skeleton. The varying degree of topline slope is a direct result of the malformation which develops in the front limbs. The tubular bones at the distal radius and ulna are the most severely affected and growth retardation is excessive. The bones of the hind limbs are much less severely affected and achieve a more normal conformation. Some chondrodysplastic animals may display near normal conformation. Diagnosis of genotype in such cases must then be made by either test-mating the animal or by blood work.

Biochemical Aspects

The chondrodysplastic animal has an associated hemolytic anemia. There are several abnormalities in the red blood cell, including greater size, increased sodium content, and a smaller percentage of solids. The chondrodysplastic also has a trace mineral imbalance, and this eventually results in an excessive accumulation of copper in the liver. Some recessive carriers exhibit the same abnormalities of the red blood cell as the chondrodysplastic, but the overlap with those of clear dogs is excessive.

Blood Profile

As noted earlier, after twelve weeks of age, radiographs no longer provide a positive diagnosis of chondrodysplasia due to changes in the carpal joint. To diagnosis an older animal, it is necessary to utilize a blood profile. Dwarfism affects more than just the front limbs. There is an associated inherited hemolytic anemia that is characterized by morphologically abnormal red cells known as “stomatocytes”. In addition to the stomatocytes, the anemia is characterized by increased red cell size (MCV), decreased mean corpuscular hemoglobin concentration (MCHC), and a normal amount of red cell hemoglobin (MCH). The red cell sodium content is increased while the percent solids is decreased. The following table summarizes some of the work done by Dr. Sheilah Fletch. A second table shows the specific values for three dwarfs. The table of ranges was originally published in the Journal of the American Animal Hospital Association. The left side of the table shows the ranges of three blood parameters (MCHC, MCV, and MCH) for the three phenotypes of the Alaskan Malamute, namely clear, carrier, and chondrodysplastic. The second table shows the same three blood parameters for three known dwarfs (Cameo, Munchkin, and Duke).

Test-Breeding

The AMCA set up a screening and control program to address the problem of chondrodysplasia in the Alaskan Malamute. Initial screening was done by means of pedigree analysis. Using the dog’s pedigree, a statistical analysis was performed based upon the number of ancestors that were either known carriers or closely related to known carriers. The analysis yielded a number expressed as a percentage. This number represented the dog’s chances of being a recessive carrier of the gene, based upon the configuration of ancestors. If the number exceeded 6.25%, the dog was considered to be in the “suspect” or “potential” category. The value of 6.25% was selected because it represented one known carrier as a great-great-great-grandparent and also corresponds roughly to a 95% confidence level (04.37%). If the pedigree analysis indicated the animal fell into the “suspect” category, two recommendations were made to the owner.

Withhold the animal from all breeding and preferably have it neutered
Withhold the animal from all breeding until it could be test-mated with a chondrodysplastic or known recessive carrier.

Another method of testing, based on the blood profile of the animal, saw limited utilization. It was considered superior to pedigree analysis but not as good as test-breeding.

Genetics

Let the symbols for the various genotypes be as follows.

dan/dan = chondrodysplastic animal
+/dan = recessive carrier
+/+ = clear animal
+/? = unknown genotype animal

In test-mating with a chondrodysplastic animal, then: (+/?) X (dan/dan) => 1/2(+/dan) + 1/2(?/dan)

If all the test puppies in the litter are radiographically normal, then ? = +, and the genotype of the unknown is statistically identified as being clear. If however one or more chondrodysplastic puppies are detected, then ? = dan, and the suspect animal is conclusively proven to be a recessive carrier. Such an animal should be removed from all further breeding, unless it is the control dog in the test-mating of another suspect animal.

Radiographing Test Litters

Test litters are normally radiographed at four to six weeks of age. A high-detail A/P projection of the distal radius and ulna of one leg is needed of each puppy in the litter. Several puppies may be included on one sheet of film, thus reducing costs for the owner. Utilization of lead or leaded vinyl/rubber sheets as film blockers (or close collimation) will avoid radiation fogging on multiple exposures. The film should be clearly marked with the owner’s name, name of sire, name of dam, number of puppies in the litter, and date of birth of the puppies. Any dead puppies that have been preserved by freezing should be radiographed at this time. These are frequently inconclusive due to age, however, and it should be understood they may not be included in statistical evaluation unless chondrodysplasia is clearly evident. [reference 8] Radiographs must be evaluated by a professional who is familiar with chondrodysplasia, and the following information should be included.

Owner’s name and address
Sire’s name
Dam’s name
Status of control animal (chondrodysplastic or recessive carrier)
Number of puppies in litter and date of birth
Number of puppies x-rayed and date of x-rays

Disposition of Test-Litter Puppies

Test-litter puppies, even though normal in appearance, must not be allowed to slip back into open breeding. Where one parent is a chondrodysplastic, all normal puppies in the test litter are recessive carriers of the gene. The AMCA approved of the following methods for handling test puppies.

Donation to institution working on problem of chondrodysplasia
Euthanasia by humane means
Early sterilization and subsequent placement in pet homes

Early sterilization encompasses tubal ligation on puppy bitches and vasectomy on puppy dogs. It is normally done between five and eight weeks of age. The AMCA produced a brochure on the early sterilization process. The only exceptions to the stated methods of disposition of test puppies would be the holding of chondrodysplastics, or possibly carriers, to be used as control animals in further test-breeding.

Blood-Testing

To a very limited extent, hematological testing was utilized as a third method of screening dogs. The process did not prove to be a valuable weapon in AMCA’s arsenal however. The necessity of baselining each laboratory’s instruments and procedures against a control group of known genotype dogs in order to establish normal values ultimately made the process infeasible. In blood testing, eleven different parameters were measured from a sample of blood. These parameters were then submitted to a statistical computer program that enhanced differences and weighted all values in order to determine the most likely genotype for that particular blood sample. Misclassification rate on the control group of fifty dogs was approximately 6% in either direction. Perhaps in the final analysis, the immensely valuable contribution of the blood test will be recognized as having conclusively demonstrated that the heterozygous animal has measurable differences from the clear animal.

Tubal Ligation and Vasectomy

This brochure, produced by the Alaskan Malamute Club of America, Inc., describes a method of rendering very young puppies incapable of reproduction. The procedures described were developed by AMCA member John Schmidt DVM and fellow veterinarian Dan F. Rice DVM. They were originally developed for the safe handling of puppies produced by test-breedings for chondrodysplasia, a genetic disorder that affects Alaskan Malamutes. For many years breeders have wanted a method of birth control that would render very young puppies incapable of breeding so that they could be sold as pets and not become a part of the breeding population. It is important to breeders to have these procedures completed before a pup is seven to eight weeks old as many prefer to make placements at that age. Such results may be obtained by salpingectomy (tubal ligation) in the bitch puppy when she is as young as three weeks old and by vasectomy in the male puppy when he is about 5 1/2 weeks old. These procedures are acceptable by the Chondrodysplasia Committee for handling puppies from test litters. Puppies should be examined carefully prior to surgery. They may be anesthetized and prepared for surgery by the standard methods used in any veterinary practice. In the female a small incision is made into the abdominal cavity caudal to the umbilicus and the ovary is elevated through the incision. The oviduct is easily seen in the mesovarium (see figure 1). It is grasped with forceps; a small section is removed and the cut ends are cauterized. The same procedure is repeated on the opposite side. Both ovaries are returned to the abdominal cavity and the abdominal incision is closed by standard methods. Please note that only a small portion of the oviduct is removed. The uterus and ovaries are left intact. Vasectomy in the male may be done as soon as the testicles are descended to the scrotum, usually when the puppy is about five weeks old. A single small midline incision is made cranial to the scrotum and a spermatic cord is elevated through the opening. A small incision is then made in the common vaginal tunic of the spermatic cord. The ductus deferens is located in a medial fold of the cord along with a small artery and vein (see figure 2 and 3). The ductus deferens is separated from the artery and vein; a small section is removed and the cut ends are cauterized. The common vaginal tunic is closed around the spermatic cord but usually no sutures are required to close this incision. The procedure is then repeated on the opposite cord. Fascia and skin are closed by standard methods. Again please note that only a small portion of the ductus deferns is removed. The testicles remain intact. Prospective owners of the pet puppies should be fully informed of the procedures that have been done. A bitch will still come into estrus and show all the signs of a normal heat. She will stand for a male but cannot conceive. It is suggested that bitches be confined when in heat and should be spayed at the usual time recommended by the veterinarian. This will prevent the undesirable manifestations of estrus and eliminate the possibility of later reproductive tract problems.

Figure 1 and 2 are from: “Anatomy of the Dog”:Miller, Christiensen & Evans. W.B. Saunders Co., Philadelphia. Figure 3: “Guide to the Dissection of the Dog”: Miller. Lithographed by Edwards Bros. Inc., Ann Arbor, Mich. Cornell Univeristy, Ithaca, New York. 1952

REFERENCES

1. Subden RE, Fletch SM, Smart ME, Brown RG “Genetics of the Alaskan Malamute Chondrodysplasia Syndrome” Journal of Heredity 63:149,1972 2. Sande RD, Alexander JE, Padgett GA “Dwarfism in the Alaskan Malamute: Its Radiographic Pathogenesis” Journal of the American Veterinary Radiology Society, 15, 1974 Sande RD, Pennock PW, Burt JK Personal correspondence, 1978 3. Sande RD Personal correspondence, 1978 4. Pinkerton PH, Fletch SM “Inherited Haemolytic Anaemia With Dwarfism in the Dog” Blood, 40:963,1972 Pinkerton PH, Fletch SM, Bruckner PJ,Miller DR “Hereditary Somtatocytosis With Hemolytic Anemia in the Dog” Blood, 44:557,1974 5. Brown RG, Hoag GN, Subden RE, Smart ME “Alaskan Malamute Chondrodysplasia I – V” Growth, Vol 41, 1977 6. Fletch SM, Pinkerton PH, Bruckner PJ “The Alaskan Malamute Chondrodysplasia (Dwarfism – Anemia) Syndrome in Review” Journal of theAmericanAnimalHospital Association, Vol 2 No. 3, 353-361,1975 7. Bourns TKR, Dodd HM, Dowdy LM, Lucus AJ, Pearson DS “The Master Plan for Control and Elimination of the Condition Known as Dwarfism” Alaskan Malamute Club ofAmerica Newsletter, November 1971 8. Sande RD, Pennock PW, Burt JK Personal correspondence, 1978 9. Schmidt JE “Tubal Ligation and Vasectomy” Brochure available from the Alaskan Malamute Club of America Online at Tubal Ligation and Vasectomy” Rice DF, Dewell CG “Sterilization of Nursing Puppies” Modern Veterinary Practice (Clinical Reports), Vol. 57, No. 10, Oct. 1976 10. Fletch, SM Personal correspondence, 1976-1977

PHOTO CREDITS

“Nori”, severely affected chondrodysplastic Photo by Bill Francis Radiographs – Radiographs of chondrodysplastic and phenotypic normal courtesy of Dept. of Radiology, Ohio State University

CONTRIBUTORS AND ADVISORS

My thanks goes to the following people who contributed their time and knowledge. Without their help and advise, this article would not have been possible.

Beckman, JM
Bourns, TKR
Burt, JK
Cox, MD
Fletch, SM</sp an>
Pearson, DS
Pennock, PW
Sande, RD
Schmidt, JE
Smart, ME

The status of obtaining a genetic test for CHD

July 8, 2012: The researchers have identified approximately 30 variants of interest in our samples, and are running these through further analysis. Additionally, they will be doing a SNP-chip genotyping study which will hopefully increase our chances to find the causative mutation. Additional new samples from carriers and an affected dog are being sent to the lab, which will help Dr. Lohi’s group confirm any findings they may uncover. We should know more in the coming few months. We have informed them that if any funds are needed to accelerate the research, we will do what is needed to provide these through the Canine Health Foundation grant process using our Donor Advised Fund. January, 2012: At the beginning of 2011, we were told that the researcher at MSU who has been working on this project for years, Dr. Pat Venta, was willing to collaborate with another researcher who had more advanced technology in an effort to find this gene.

Unfortunately, several months later we were informed that he had decided against this collaboration and wanted to pursue a grant on his own to do the research. At this time no grant has been pursued. Because finding the gene for dwarfism is a priority, we are exploring all other options for this research. Dr. Hannes Lohi at the University of Helsinki discovered the gene for dwarfism in Norwegian Elkhounds, but samples from our dwarfs have found that this is not the same gene. However, his research team has taken on finding this gene in our breed-at no cost. We have gathered samples from all currently living dwarfs and dwarf carriers and have shipped the majority of these to their facility in Helsinki. These samples have been run through a whole exome scan platform, which is the most advanced genetic analysis available. They hope to have the results from this in a few months, at which time they will look for abnormalities which may represent the gene for the disease. How long this will take depends completely upon what the genetic results look like, but we feel confident that this team is doing everything that can be done on this project as quickly as is possible. They have been extremely responsive to any questions we have, and have been very proactive in asking us questions as well as getting any samples into their lab. If any new dwarfs are identified, we desperately need DNA from these dogs for our research study. If you have any samples to contribute or questions, please feel free to contact: Sandi Shrager AMCA Health Committee Chair sandis@u.washington.edu 206-919-8103206-919-8103 Kaisa Kyostila kaisa.kyostila@helsinki.fi Ranja Eklund/Lohi Laboratory Biomedicum Helsinki, room B320 Haartmaninkatu 8 00290 Helsinki Finland Below is a table with descriptions of the type abbreviations used in the database:

Chondrodysplasia

Chondrodysplasia is a genetic disorder in the Alaskan Malamute which manifests itself in puppies born with deformities, eventually evident in the abnormal shape and length of their limbs. Chondrodysplasia is present in adult carriers as an auto-somal or simple recessive gene. Therefore, both sire and dam must carry this gene in order to produce an affected (chondrodysplastic) puppy. As Malamute owners and prospective owners, we have an opportunity to control the proliferation of Chondrodysplasia in the Alaskan Malamute, and with such control, there is hope of its total elimination in our breed.

History and Explanation

For a number of years, Alaskan Malamute breeders in both the United States and Canada were aware of occasional litters that contained deformed or “dwarf puppies”, produced by parents who showed no physical evidence of the condition. It was not until the early 1970’s that these puppies were conclusively proven to be the manifestation of a genetic disorder. At first, these affected dogs were known as “dwarves” because of their diminutive size. This term gave rise to considerable confusion. Veterinarians associated it with the dwarfism found in Hereford cattle, while owners associated it with any small Malamute. Since neither is correct, another name, Chondrodysplasia(meaning “faulty cartilage”), was coined and brought into usage. Chondrodysplasia in the Malamute was originally diagnosed as a form of rickets. Upon closer examination at various veterinary schools, it was determined that this diagnosis was incorrect. While it isn’t known exactly what this crippling problem is, it has definitely been proven to be genetic, or inherited. A more technical description of this gene is “auto-somal,” or “simple recessive.” This simply means that the sire and dam must both carry this gene in order to produce an affected chondrodysplastic puppy. In very young puppies, under six weeks of age, the deformity is often very difficult, if not impossible, to detect without x-rays, even to the practiced eye. But as the puppies grow older, the deformity becomes more evident in the shape and length of the front legs. However, not all chondrodysplastics are severely affected. In some adults, the front legs may appear “almost” normal. It is not the chondrodysplastics themselves that are the major problem. The greatest concern is the use in breeding of the completely normal appearing dogs that possess or “carry” this gene. (A good parallel of this among humans is two brown-eyes parents producing a blue-eyed baby. In spite of their brown eyes, the parents both “carry” the gene for the blue eye.) While the breeding of two carriers can produce a chondrodysplastic, a litter from a breeding between a carrier and a “non carrier” (or clear) will contain only normal appearing dogs. Nevertheless, an undetermined number of puppies will themselves be carriers, having inherited the gene from their carrier parent. The continued whelping of such litters increase the number of carriers “at large” in the total Malamute population.

Chondrodysplasia Certification Registry

CHD Certification is available to dogs with one certified ancestor between the applicant dog and each uncertified ancestor. If proof can be offered that an uncertified ancestor is a full sibling to a certified dog, the applicant’s pedigree will be evaluated. It should be noted that certification can be revoked when information is verified that a dog was mis-classified through subsequent breedings and/or test breedings. Sometimes the pedigree reveals the dog to be non-certifiable with regards to Chondrodysplasia. In such cases, the AMCA recommends these dogs not be bred. The owner may feel the dog to be a great asset to a breeding program, or the dog may already have offspring who are themselves now affected by the un-certifiable status of the parent. In such circumstances, the owner may choose to apply for a further screening process known as “Test Breeding”. The certificate is not proof that a dog is clear
(i.e. not a carrier), but only that the probability that it is is calculated to be below 6.25%. AMCA is supporting genetic research programs with the intent of finding a DNA marker allowing the proof that a dog is either clear of this genetic disorder or is not. Whenever this test is available, then there will no longer be a need for test breeding to track this condition.

Test Breeding

The committee will assist the owner in this choice. At present, test breeding a suspect Malamute to a Chondrodysplastic, or to a known carrier, is the only means to be reasonably certain the dog is not a carrier of the gene. Should the owner decide to enter the suspect dog into a test breeding program, a contract specifying certain criteria is entered into with the AMCA Chondrodysplasia Certification Committee. The Committee Chairman and Area Representatives are available for consultation regarding the procedures for test breeding. Once thought to occur only in Malamute, Chondrodysplasia has now been detected in other breeds and the AMCA program has become a model for other breed clubs. Your efforts are needed if it is to continue to fulfill its vital leadership role. We hope you will join us in the fight to control this genetic disorder. It is essential for the prospective malamute purchaser of potential breeding stock to realize the importance of these certificates. By purchasing from AMCA Certified stock, the buyer not only is helping the breed cull out Chondrodysplasia, but is also relieving himself of the responsibility of test breeding.

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The Status of Obtaining a Genetic Test for Chondrodysplasia

Dr. Lohi has released the following Report to the Canine Health Foundation on the current progress of our research project.

Report to Grant Sponsor from Investigator:

“In the Alaskan Malamute chondrodysplasia study, we have been using two complementary research methods to discover the causative mutation: exome sequencing and DNA-marker based genome-wide association mapping. Thus far we have analyzed genome-wide data from ten affected dogs and up to 87 healthy control dogs.

Part of the control cohort was obtained from a previous cataract study. The Alaskan Malamute chondrodysplasia is thought to have an autosomal recessive mode of inheritance and we have performed our data analyses under this model. We have now identified a chromosomal region that shows association to the disease. This region was identified by using several different genome-wide analysis approaches, which included both basic case-control association and family-based methods.

The finding is still tentative because our sample cohort has some issues concerning unwanted population structure. The affected dogs form a separate cluster from the control samples, which means that they come from a separate line of dogs than the control dogs. This population structure can have an effect to the results by introducing false positive findings that are caused by the population difference and not by the difference in affection status.

To correct this problem, we have recently genotyped a new sample set of seven affected and seven control dogs but unfortunately half of these sample failed because of their poor quality. We have previously performed exome sequencing to one carrier dog and two affected dogs, and now we are in theprocess of sequencing four additional affected and two additional carrier dogs by using an updated exome sequencing platform.

The main obstacle in this study has been the availability and quality of samples. Many samples of affected dogs have been received as old DNA samples that have had both low DNA-quality and quantity. Furthermore, control dogs that are closely related to the affected dogs have been difficult to obtain, and this has caused the problems in population structure.

Consequently, any new samples from affected dogs and their relatives would be greatly appreciated. However, people within the Alaskan Malamute breed have been extremely supportive of the research project, and we wish to warmly thank all who have contributed to the study and helped us in obtaining samples.”

Dr. Lohi’s research group has just received a set of samples from Dr. Venta’s original research project. This represents a number of additional affected and carrier dogs and should greatly facilitate the research project and progress.

Dr. Lohi has applied for and received an Acorn Grant through the American Kennel Club’s Canine Health Foundation to help facilitate the research project. This grant has been fully funded by the Alaskan Malamute Research Foundation.

http://www.akcchf.org/research/funded-research/1901.html

The researchers have checked 28 variants from the exome-data in a bigger sample cohort but unfortunately none of these variants showed perfect segregation with the disease. They are currently performing the lab work to check another set of 27 variants (ioinformatician re-analyzed the exome-data with another program and with some new interesting variants that they are looking through).

The researchers have identified approximately 30 variants of interest in our samples, and are running these through further analysis. Additionally, they will be doing a SNP-chip genotyping study which will hopefully increase our chances to find the causative mutation.

Additional new samples from carriers and an affected dog are being sent to the lab, which will help Dr. Lohi’s group confirm any findings they may uncover. We should know more in the coming few months. We have informed them that if any funds are needed to accelerate the research, we will do what is needed to provide these through the Canine Health Foundation grant process using our Donor Advised Fund.

At the beginning of 2011, we were told that the researcher at MSU who has been working on this project for years, Dr. Pat Venta, was willing to collaborate with another researcher who had more advanced technology in an effort to find this gene. Unfortunately, several months later we were informed that he had decided against this collaboration and wanted to pursue a grant on his own to do the research.

At this time no grant has been pursued. Because finding the gene for dwarfism is a priority, we are exploring all other options for this research. Dr. Hannes Lohi at the University of Helsinki discovered the gene for dwarfism in Norwegian Elkhounds, but samples from our dwarfs have found that this is not the same gene. However, his research team has taken on finding this gene in our breed–at no cost.We have gathered samples from all currently living dwarfs and dwarf carriers and have shipped the majority of these to their facility in Helsinki.

These samples have been run through a whole exome scan platform, which is the most advanced genetic analysis available. They hope to have the results from this in a few months, at which time they will look for abnormalities which may represent the gene for the disease. How long this will take depends completely upon what the genetic results look like, but we feel confident that this team is doing everything that can be done on this project as quickly as is possible. They have been extremely responsive to any questions we have, and have been very proactive in asking us questions as well as getting any samples into their lab.

What to do if you think you have a chondrodysplastic puppy?

First of all, do not panic.

Dogs affected with Chondrodysplasia live long and happy lives, and are no less a perfect pet than any other Malamute. Indeed, many who have owned affected dwarf Malamutes say that they have been their favorite pets!

And if you are a breeder, please know that this is NOT something you should feel ashamed of, or try to hide. The more open we as breeders are about the prevalence of this disease, the more we can learn from one another. Additionally, right now our research project is in DESPERATE need of samples of confirmed affected dogs and their carrier parents or other close relatives.

ANY help you can give in providing these samples will be greatly appreciated, and help speed along our search for a genetic test for Chd.

ANY help you can give in providing these samples will be greatly appreciated, and help speed along our search for a genetic test for Chd. If you are concerned that you might have a puppy affected with Chondrodysplasia, the Health Commitee of the AMCA is very willing to help and assist you in any way possible.

We will assist with instructions on xraying of puppies and collection of blood or DNA for shipment to our researchers in Helsinki as well as for banking with the Canine Health Information Center (in the event stored DNA becomes necessary to access). If financial assistance is needed to accomplish this, we will provide what is needed. All queries will be kept confidential if this is requested. Please contact Sandi Shrager at sandis@u.washington.edu.

We will arrange for xrays to be done, evaluated by a board-certified radiologist, and blood/DNA to be collected for shipping and storage. These are simple procedures that we are very willing to provide any help with. ALL QUERIES WILL BE KEPT CONFIDENTIAL AND NOT DISCLOSED TO ANYONE OTHER THAN THE HEALTH COMMITTEE CHAIR IF THIS IS REQUESTED. Procedures for the identification of Chondrodysplasia Chondrodysplasia can only be diagnosed by xray of puppies between 4-12 weeks. If you think you have an affected puppy, it is critical to have these xrays done within that timeframe. Xrays of the elbows distal in Cr/Ca and Lateral projection will be needed for evaluation by a certified radiologist. Examples of good xrays are provided here:

If any other littermates to the puppy you are concerned about are still living with you, it would also be best to have them xrayed and evaluated as well, as many dogs are not as clearly affected as others, and all information about a litter is important to ascertain. Multiple puppies can be xrayed on one film.

Most veterinarians have board certified radiologists that they use to read xrays. If your veterinarian does not have a board-certified radiologist available, a list may be found at www.acvr.org If the puppy or puppies are confirmed to have Chondrodysplasia, any littermates should also be xrayed by 12 weeks of age. Blood (5 ml EDTA + 3 ml EDTA) should be collected on all puppies, their parents if available, and any grandparents.

This MUST be kept refrigerated prior to shipping. Shipping should occur within several days of collection, and samples sent to:

1) 5-10 ml to the Canine Health Information Center DNA storage bank. Contact your veterinarian to make arrangements to have blood drawn.

This can be done at an appointment made specifically for this purpose, or you can arrange to have the blood drawn during some other regularly scheduled visit. Be sure to tell your veterinarian the blood sample is to be used for research purposes. Many veterinarians will then do the procedure at a reduced rate or at no cost.

Take your dog and ask that a sample of 5 to 10 cc’s of whole blood be drawn into EDTA purple top tubes. If collecting multiple samples, please take care to ensure matching the correct samples with the correct names.

3. The blood sample only needs to be put in the tubes and rocked gently a few times to distribute the anticoagulant. The sample should NOT be spun, have serum extracted, or have anything further done to it.

4. Ship the sample via an overnight delivery service to the University of Missouri (address below). DO NOT ship samples on Fridays, as there will be no one available at the lab to receive the sample on Saturday.

5. The sample should be shipped using cool packs, and ideally should be shipped immediately. If samples are held for a day or over a weekend before shipping, they must be refrigerated.

6. Complete the application form/health survey for each dog and send it to the OFA using the OFA mailing label provided. The health survey is a critical part of the repository. The samples are of little value without the corresponding phenotypic history and genealogy. It is critical to note on the application form that the sample corresponds to a Chd affected dog, or a carrier.

If there are any significant health changes for this dog in the future, please email the OFA at ofa@offa.org with the update. ALL BLOOD SAMPLES FOR CHD AFFECTED DOGS OR THEIR CARRIER RELATIVES MUST BE ACCOMPANIED BY A RADIOLOGIST’S FORMAL REPORT.

1) 3ml EDTA to research group in Helsinki. In the sample shipments you need to include a proforma (for the US authorities) and an import permission (for the Finnish customs). You will find these attached. You need to put these two on a plastic pouch to the outside of an envelope or a box in which you are sending the samples.

On the proforma you will need to add your name and signature and contact info. Nothing needs to be added to the import permission. (it’s a few things to remember but these forms are needed for shipping from the US to Finland). If it is possible, we would recommend you send the samples for example using Fedex. In the Fedex form you need to put the value of the shipment to $1 and specify that you are sending released animal specimens (UN3373). You could use also international priority but there’s less guarantee that the shipment will arrive in reasonable time.

The blood should be shipped chilled. Sample to Helsinki Import Permissions English Blood Sample Form ALL BLOOD SAMPLES FOR CHD AFFECTED DOGS OR THEIR CARRIER RELATIVES MUST BE ACCOMPANIED BY A RADIOLOGIST’S FORMAL REPORT. PEDIGREE IS ALSO REQUESTED AS WELL AS DETAILS ON HOW SAMPLES ARE RELATED TO ONE ANOTHER (IF MORE THAN ONE SAMPLE SUBMITTED).

Shipping address: Ranja Eklund/Lohi’s Research Group, Biomedicum Helsinki, Haartmaninkatu 8, 00290 Helsinki, FINLAND Kaisa Kyostila If there are any questions regarding any step in this process, or if assistance from AMCA is requested, these may be addressed to: Sandi Shrager PO Box 25111 Seattle, WA 98165

Email: sandis@u.washington.edu Phone: 206-919-8103 While Sandi Shrager will maintain all confidentiality if requested, if you would prefer to work directly with CHIC and Dr. Lohi’s research group, the contact information for these are below: Kaisa Kyostila kaisa.kyostila@helsinki.fi Ranja Eklund/Lohi Laboratory Biomedicum Helsinki, room B320 Haartmaninkatu 8 00290 Helsinki Finland CHIC Questions regarding the CHIC program may be addressed to: Eddie Dziuk or Dr. Greg Keller Orthopedic Foundation for Animals, Inc. 2300 East Nifong Blvd. Columbia, MO 65201-3806 (800) 442-0418 Email: chic@offa.org

Chondrodysplasia 2012

CHD research update

The researchers have checked 28 of the variants of interest, unfortunately none have proven to be the suspect gene. They are currently preparing lab work to check another set of 27 variants, and have a simultaneous SNP chip process running to identify other potential genes. They will keep us updated on a regular basis and are preparing a study flyer for us to distribute and post on the website.

Documents

Relative Risk Analysis

Closest Common Ancestor

Report from the Chondrodysplasia Certification Committee

As many of the members are aware, a dwarf (Chondrodysplastic) puppy has been produced in an open breeding between dogs with very low probabilities. The pedigrees of these dogs do not have any obvious ancestor with a high probability or unknown background. This has made it necessary to revoke temporarily the certificates issued to many of the dogs in these pedigrees. We are in the process of arranging some test breedings to help determine where the gene is coming from so we can reinstate the certifications for dogs not involved. There are very few carriers/dwarfs available for test breeding, so dogs that are closest to the affected dog will be test bred first. It is important to remember that our certification program is based on probabilities. A probability below 6.25 means that it is unlikely that the dog carries the gene. This does not mean that we are certain this dog does not carry the gene. Even dogs that have been test bred, still have a probability for carrying the gene, albeit a very low probability. The littermates of the dogs who are in this pedigree are as affected as the dogs themselves, that is why the littermates have also had their certificates revoked. Dogs in this pedigree that have been test bred and cleared by this retain their probability from their test breeding results. How did we arrive at the new probabilities? Starting with the parents of the puppy, they are carriers so their probability is now 100%. Each generation behind them the probability is cut in half, so their parents are 50%, grandparents 25%, great-grandparents 12.5 % and by the 4thgeneration this becomes 6.25% which is the level chosen for issuing certificates when this program was begun in the 1970’s. There is a series of excellent articles on this whole program written by Linda Dowdy on the Minnesota Alaskan Malamute Club website. Dan Anderson has done his best to provide a complete list of the dogs affected by this situation. It is possible that he has missed some dogs, so please bear with us as we may have to add dogs later. AMCA will be contacting all of these dog’s owners to inform them of the change of status of their dogs with regard to Chondrodysplasia. With the assistance of the Canine Health Foundation, the CCC and the Health Committee have been working with a research group in Helsinki,Finland for the past year to find the gene for Chondrodysplasia. This group identified the gene for Norwegian Elkhound dwarfism, so we have high hopes that they will find our gene as well. DNAf rom all of the dogs directly involved in this pedigree is being sent to Helsinkito facilitate their work. Please see the Health Committee Column as well as the AMCA website for updates on this project. In the meantime, what is a breeder to do? I would recommend that the breeders do the breedings they have planned. If they are breeding dogs with a close relationship to the dogs in the affected pedigree, they can x-ray their puppies to make sure they have not produced a dwarf. These x-rays are simple, inexpensive and should be done when the pups are between 5-12 weeks. The x-rays can be sent to Dr Sande who will then issue a letter with his official opinion which the breeder can use if need be to show that the pups are not affected. This is not a test breeding, but would help to identify affected puppies if any are produced. All of the information you need to x-ray puppies and even reading the x-rays is available on the Minnesota Malamute website. Our Code of Ethics does not preclude breeding dogs with high probabilities, it says that you must be honest with the puppy buyers and the owner of the dog you are breeding to. Chondrodysplasia is only one of the many problems affecting our breed. We all have to make the best decisions we can with the knowledge we have. We hope to have results of some of the test breedings planned within the next 8-12 months. This may result in dogs’ certifications getting reinstated. If the Helsinki group gets lucky and find the gene quickly, then everyone can test their dogs and breed carriers to non-carriers and not narrow down our gene pool even more than it is. Please thank the owners of these dogs for allowing us to publish their pedigrees and for all of their cooperation in a very difficult situation. We need to have everyone’s support if we are going to eradicate Chondrodysplasia. These are the pedigrees of the sire and dam of the litter which included a puppy whose x-rays were examined by Dr. Sandee and deemed to be affected by Chondrodysplasia.

The sire is Ch Bearhug’s Artic Bob Cat, known as Bob

The dam is Mimmenuk’s Dancin’In The Dark, known as Layla.

The name of the dwarf pup is Mimmenuk’s U Rock My World, known as Jackson, born May 4, 2012.

Chondrodysplasia, An Overview and Current Approach to Breeding Management

In the late 1960’s a condition known as “dwarfism” (aka Chondrodysplasia, or ChD) was identified as an autosomal recessive condition in the Alaskan Malamute, with an apparent high incidence in certain lines.

Chondrodysplasia is a genetically-determined skeletal disorder that occurs primarily in the purebred Alaskan Malamute. The chondrodysplastic Malamute displays in varying degrees the following phenotypic characteristics.

1) Excessively shortened front limbs with various degrees of bowing and deformity, especially the radius and ulna
2) A topline that slopes from the pelvis down to the withers

Some chondrodysplastic Malamutes display a severe degree of deformity while others display almost no visible characteristics. This condition is only able to be diagnosed/confirmed by examination of x-rays of the lower front limb (distal ulna) at an early age (prior to growth plate closure). Looking at physical attributes of the dog, such as limb deformity or short stature does not confirm or refute a case of ChD since several other conditions can result in the same physical appearance and a mildly affected dog may show no outward physical abnormalities.
As a result, the AMCA introduced what was, at that time, a cutting edge, ground-breaking program to try to eliminate the condition from the breed. With this knowledge, experts in radiology, genetics and the breed came together to provide a workable system that would reduce the incidence of carriers and, they hoped, eliminate the condition in the Alaskan Malamute.

This program was based on test-breeding dogs and calculating a theoretical (mathematical) probability that a dog was not a carrier based on the number of puppies produced when an individual was bred to an affected dog or a carrier, providing that all puppies produced were screened by x-ray at 6 to 8 weeks of age and that none of the pups were affected by the condition. The cut-off point, based on pure practicality, where a dog was considered “OK/approved to breed” was at a probability of 6.25% mathematical risk of being a carrier.

This program was very successful in reducing the incidence of carriers (and the “bad gene”) in the breed from quite prevalent in certain lines to rather rare in the population as a whole. It has resulted in bringing the overall probability within the population down to under 6.25% overall. After many generations of breeding low probability dogs, today there is no selection pressure on “certified” dogs to reduce this any further. Based upon information provided by Dr. Jerold S. Bell, DVM, at

Tufts University, it was also determined that many of the probabilities assigned to modern day dogs were based upon historical numbers so many generations removed that they did not represent an accurate reflection of risk. It is also apparent from the results of survey to Alaskan Malamute breeders worldwide that the incidence of this condition is very low in the Malamute population and the certification program therefore no longer helped to reduce the risk of producing an affected dog in the general population.

It is important to realize that even test-bred dogs carry SOME risk, it was known from the start by those that set up the original program that some carriers would slip through due to the theoretical nature of the calculation and the practical aspects of finding a compromise cut-off that allowed the breed to still exist.

It is important to realize that even test-bred dogs carry SOME risk

Thus, we have carriers in the current breeding population, albeit at very low levels. It was the confirmation of a dwarf being produced from certified parents that created the impetus to revisit the program and the formation of a working group to propose alternative methods of addressing this genetic disease.

Based on information received from the eminent geneticist Professor Jerold S Bell DVM at Tufts University, a review of programs/methods used to control autosomal recessive genes by other dog clubs (and even other conditions in Alaskan Malamutes outside of the US), and a world-wide survey of Malamute owners and breeders, it was recommended that AMCA change the approach to handling this genetic disease. These recommendations are predicated on the very low incidence of the condition in the breed as a whole, the lack of significant morbidity or suffering of affected dogs and the sincere wish/hope that the members of AMCA can develop and foster an open, respectful and mutually beneficial understanding between all breeders and owners that works in the best interests of the breed in the long-term.

The recommendations of the working group were brought to a membership vote, with the result a majority vote to approve these. As a result, the following changes have been implemented:

1)    The previously mandated ChD certification program (test-breeding and certification) and the CCC were permanently retired.
2)    The breeder’s Code of Ethics was changed to reflect the recommendations of the working group/AMCA policy (breeders are no longer required to have Chd certification on breeding stock as this option no longer exists)
3)    AMCA will establish an open database of confirmed carriers and affected dogs. (**Note**this is still in development. However, only four currently living dogs in open breeding are confirmed to be carriers as of May, 2014. Living carriers resulting from old test-breeding are not included in this list as they will not be used for future breeding.).
a)    A confirmed carrier means a dog that has produced one or more confirmed (by expert x-ray analysis) affected dog(s)
b)    The database is intended to be prospective but can include any confirmed carriers/affected dogs identified under the conditions in parts d) and e) below.
c)    The database will be made available to both members and non-members of AMCA.
d)    Dogs included in the database must be identified/submitted by the owner or breeder of record to be accepted
e)    The diagnosis must be confirmed by radiograph and a written report by a Board-certified (or equivalent expert*) Veterinary Radiologist
f)    The database shall include the registered name, breed registry used (e.g. AKC) and registration number, date of birth, and gender of each confirmed carrier/affected dog;
g)    Database information (carrier/affected-status of a dog) shall be considered public information and may be included in pedigree programs, such as that produced by AMAL
4)    AMCA now focuses on providing recommendations, guidelines and
education to help breeders, including (but not limited to) the
following:
a)    AMCA provides clear information on x-ray screening to detect/confirm affected dogs and makes the following recommendations with respect to screening “high risk” litters:
i)    X-ray one carpus (wrist), one view, at between 6 and 12 weeks of age
ii)    Submit x-rays to OFA, or other Board-certified (or equivalent expert*) Veterinary Radiologist for evaluation
iii)    The following puppies are considered “high risk” and should be examined to gain maximum information:
(1)    Offspring of known carriers
(2)    Offspring of siblings to known/confirmed affected dogs
(3)    All puppies in a litter (provided they are not older than 16 weeks) with at least one confirmed affected puppy
b)    AMCA provides updated and ongoing educational materials/opportunities for owners and breeders including support to help breeders & owners understand genetic disease, genetic principles of breeding, and to remove the fear/stigma of producing an affected dog (with any genetic disease, not just ChD)
i)    Provide educational seminars, web-based learning and/or published articles in the newsletter to keep members informed about the latest knowledge and understanding of genetic diseases and their control ii)    Encourage openness & collaboration amongst breeders
and owners

Please note that the Alaskan Malamute Club of America is working actively with Dr. Hannes Lohi and the American Kennel Club Canine Health Foundation to develop a genetic test for Chondrodysplasia. *** DNA of any affected dogs or their known carrier aren't is needed to help contribute to this research project.***

Alaskan Malamute Club of America

The AKC Parent Breed Club

Chondrodysplasia