Origin & Description:
A breeding program to develop the Miniature Australian Shepherd (North American Miniature Australian Shepherd) was begun in 1968 using small Australian Shepherds. Breeders bred them down in size to produce a smaller dog and today continue to strive to produce a mirror image of the Australian Shepherd in a size that fits well into today's lifestyle, without sacrificing instinct, ability or character.
The Miniature Australian Shepherd is a breed that was developed by breeding smaller Aussies for multiple generations to reach this desired size. Mini Aussies are increasing in popularity among those interested in a compact dog with a strong work ethic. They have a smooth medium-length double coat, with a short dense undercoat. The outer coat is close and rain resistant. Aussies come in blue or red Merle, red or black Bi, (with white no tan markings) red or black tricolor, (all with white and tan markings). The hair around the ears and eyes should not be white. The coat may be straight or slightly wavy, and should have feathering on the back of the legs, and a mane and frill around the neck. Hair on the head, front of the forelegs and on the outside of the ears is shorter than the rest of the coat. The hindquarters are the same length as the forequarters. The top of the skull is quite flat and clean cut. The feet are oval and compact. The lips do not hang over the lower jaw. "The Mini Aussies tail" Some of the reasons are tradition, function, identification and cosmetic. Consequently, tail docking was implemented to avoid injury & infection when dogs assisted men in herding or hunting. Their tails were a magnet for fox tails, burrs and stickers which can cause trauma to the tail. One of the reasons natural bobtails were valued and bred for.
A breeding program to develop the Miniature Australian Shepherd (North American Miniature Australian Shepherd) was begun in 1968 using small Australian Shepherds. Breeders bred them down in size to produce a smaller dog and today continue to strive to produce a mirror image of the Australian Shepherd in a size that fits well into today's lifestyle, without sacrificing instinct, ability or character.
The Miniature Australian Shepherd is a breed that was developed by breeding smaller Aussies for multiple generations to reach this desired size. Mini Aussies are increasing in popularity among those interested in a compact dog with a strong work ethic. They have a smooth medium-length double coat, with a short dense undercoat. The outer coat is close and rain resistant. Aussies come in blue or red Merle, red or black Bi, (with white no tan markings) red or black tricolor, (all with white and tan markings). The hair around the ears and eyes should not be white. The coat may be straight or slightly wavy, and should have feathering on the back of the legs, and a mane and frill around the neck. Hair on the head, front of the forelegs and on the outside of the ears is shorter than the rest of the coat. The hindquarters are the same length as the forequarters. The top of the skull is quite flat and clean cut. The feet are oval and compact. The lips do not hang over the lower jaw. "The Mini Aussies tail" Some of the reasons are tradition, function, identification and cosmetic. Consequently, tail docking was implemented to avoid injury & infection when dogs assisted men in herding or hunting. Their tails were a magnet for fox tails, burrs and stickers which can cause trauma to the tail. One of the reasons natural bobtails were valued and bred for.
Temperament:
Miniature Australian Shepherds are easy going, fun puppies that love to play. Courageous, loyal and affectionate, they are excellent children's companions that are great with active children. A devoted friend and guardian. Very lively, agile and attentive, they are eager to please with a sixth sense about what the owner wants, intelligent and easy to train. They can become nervous and destructive if left alone too much without enough mental & physical exercise. They need a job to do, as the breed is very intelligent, active and thus easily bored. Socialize your dog well when it is a puppy to avoid it becoming suspicious of strangers. Some like to nip people’s heels in an attempt to herd them. They need to be taught herding humans is not acceptable. A fine companion, it also enjoys working small stock. They are quiet workers. This breed is not usually dog aggressive, although suspicious glint character. Make sure you are this dog's firm, confident, consistent pack leader to avoid Small Dog Syndrome, human induced behavior problems. Always remember, dogs are canines, not humans. Be sure to meet their natural instincts as animals.
Miniature Australian Shepherds are easy going, fun puppies that love to play. Courageous, loyal and affectionate, they are excellent children's companions that are great with active children. A devoted friend and guardian. Very lively, agile and attentive, they are eager to please with a sixth sense about what the owner wants, intelligent and easy to train. They can become nervous and destructive if left alone too much without enough mental & physical exercise. They need a job to do, as the breed is very intelligent, active and thus easily bored. Socialize your dog well when it is a puppy to avoid it becoming suspicious of strangers. Some like to nip people’s heels in an attempt to herd them. They need to be taught herding humans is not acceptable. A fine companion, it also enjoys working small stock. They are quiet workers. This breed is not usually dog aggressive, although suspicious glint character. Make sure you are this dog's firm, confident, consistent pack leader to avoid Small Dog Syndrome, human induced behavior problems. Always remember, dogs are canines, not humans. Be sure to meet their natural instincts as animals.
Height and Weight:
Toy Height: 10 - 14 inches (26 - 36 cm)
Toy Weight: 12 - 17 pounds (5.5 - 8 kg)
Miniature Height: 13 - 18 inches (33 - 46 cm)
Miniature Weight: 20 - 40 pounds (9 - 18 kg)
Toy Height: 10 - 14 inches (26 - 36 cm)
Toy Weight: 12 - 17 pounds (5.5 - 8 kg)
Miniature Height: 13 - 18 inches (33 - 46 cm)
Miniature Weight: 20 - 40 pounds (9 - 18 kg)
Health Problems:
The gene for the beautiful Merle coloration can carry a blind/deaf factor. This may be expressed only in Merle/Merle crosses. (which we do NOT do) The vast majority of Merle North American Miniature Australian Shepherds are heterozygous Merle (one parent is Merle, the other is solid) and these Merle's are not at risk for any special health problems due to their coloration. Some herding dogs carry a MDR1 gene which makes them sensitive to certain drugs that are otherwise okay to give another dog, but if tested positive for this gene can kill them.
The gene for the beautiful Merle coloration can carry a blind/deaf factor. This may be expressed only in Merle/Merle crosses. (which we do NOT do) The vast majority of Merle North American Miniature Australian Shepherds are heterozygous Merle (one parent is Merle, the other is solid) and these Merle's are not at risk for any special health problems due to their coloration. Some herding dogs carry a MDR1 gene which makes them sensitive to certain drugs that are otherwise okay to give another dog, but if tested positive for this gene can kill them.
Living Conditions:
The Miniature Australian Shepherd will do okay in an apartment if it is sufficiently exercised. They are moderately active indoors and will do okay with a small yard. This breed does well in cold climates. The Mini Aussie enjoys to be taken on walks, even to the park to fetch a ball. This energetic little dog needs plenty of vigorous exercise to stay in shape, or better yet, some real work to do. Although they toy and/or Miniature Australian Shepherds are just as happy getting loved and being a lap dog, They excel at and enjoy obedience, fly ball, agility, disc dog and can also serve as a service therapy dog. Most of the teaching, training and redirecting begins in your home.
Life Expectancy:
About 12-13 years.
Grooming:
The coat of the Miniature Australian Shepherd is easy to groom and needs little attention. Brush occasionally with a firm bristle brush and bathe only when necessary. This breed is low is dander & if kept clean and groomed they are an average shredder.
The Miniature Australian Shepherd will do okay in an apartment if it is sufficiently exercised. They are moderately active indoors and will do okay with a small yard. This breed does well in cold climates. The Mini Aussie enjoys to be taken on walks, even to the park to fetch a ball. This energetic little dog needs plenty of vigorous exercise to stay in shape, or better yet, some real work to do. Although they toy and/or Miniature Australian Shepherds are just as happy getting loved and being a lap dog, They excel at and enjoy obedience, fly ball, agility, disc dog and can also serve as a service therapy dog. Most of the teaching, training and redirecting begins in your home.
Life Expectancy:
About 12-13 years.
Grooming:
The coat of the Miniature Australian Shepherd is easy to groom and needs little attention. Brush occasionally with a firm bristle brush and bathe only when necessary. This breed is low is dander & if kept clean and groomed they are an average shredder.
What is a “Carrier” of a Recessive disease?
Recessive inherited diseases are those in which an individual must inherit two copies of a mutated gene (one from each parent) in order to develop the associated condition. Dogs inheriting two copies of the mutation are typically not recommended for breeding because even if bred to a dog that does not have the same genetic mutation, every puppy from the litter would inherit a single copy of the disease-associated mutation, thereby increasing the frequency of the mutation in the breed population to a significant degree.
Dogs inheriting one copy of the mutation from a single parent are considered “carriers” of the disease and will not develop clinical signs of the disease themselves. However, when bred with another dog which carries the same mutation, approximately 25% of the offspring will inherit two copies of the mutation and will be at risk for or affected with the associated condition. Therefore, in general, it is recommended to only breed a carrier to a dog that is clear of the mutation. Using statistics as a guide, this strategy is expected to result in a litter consisting of approximately 50% carrier offspring and 50% normal or “clear” offspring. Thus, avoiding the removal of the carrier dog and its unique combination of genetic variants that contribute to the overall genetic diversity of the breed while limiting the number of puppies born with the known, disease-associated mutation.
Recessive diseases are particularly troubling for breeders because dogs inheriting a single copy of a disease-causing mutation (“carriers”) do not show signs of the disease, but can produce puppies with the disease if bred to another carrier of the same mutation. When it comes to genetic diseases, Ben Franklin had it right when he stated, “An ounce of prevention is worth a pound of cure.” In a perfect world in which every dog breeder performed genetic disease testing on their breeding stock and made selective breeding decisions using these results, diseases caused by over 200 known canine genetic mutations could be completely prevented
Recessive inherited diseases are those in which an individual must inherit two copies of a mutated gene (one from each parent) in order to develop the associated condition. Dogs inheriting two copies of the mutation are typically not recommended for breeding because even if bred to a dog that does not have the same genetic mutation, every puppy from the litter would inherit a single copy of the disease-associated mutation, thereby increasing the frequency of the mutation in the breed population to a significant degree.
Dogs inheriting one copy of the mutation from a single parent are considered “carriers” of the disease and will not develop clinical signs of the disease themselves. However, when bred with another dog which carries the same mutation, approximately 25% of the offspring will inherit two copies of the mutation and will be at risk for or affected with the associated condition. Therefore, in general, it is recommended to only breed a carrier to a dog that is clear of the mutation. Using statistics as a guide, this strategy is expected to result in a litter consisting of approximately 50% carrier offspring and 50% normal or “clear” offspring. Thus, avoiding the removal of the carrier dog and its unique combination of genetic variants that contribute to the overall genetic diversity of the breed while limiting the number of puppies born with the known, disease-associated mutation.
Recessive diseases are particularly troubling for breeders because dogs inheriting a single copy of a disease-causing mutation (“carriers”) do not show signs of the disease, but can produce puppies with the disease if bred to another carrier of the same mutation. When it comes to genetic diseases, Ben Franklin had it right when he stated, “An ounce of prevention is worth a pound of cure.” In a perfect world in which every dog breeder performed genetic disease testing on their breeding stock and made selective breeding decisions using these results, diseases caused by over 200 known canine genetic mutations could be completely prevented
Prevention Is Smart Breeding- Collie Eye Anomaly and the Australian Shepherd by Casey Carl
Despite a name which implies an origin “down under”, the Australian shepherd is widely understood to be a breed of American origin. In fact, descriptions of the breed and their importance in the lives of 19th and 20th century Basque shepherds who had relocated from Australia to the western US are plentiful. Australian shepherds’ exceptional intelligence, versatility, desire to please, and a natural instinct to herd and guard livestock have made them a common inhabitant of ranches and farms where they have been trained to perform a variety of tasks. Aside from their work on the homestead, their unique abilities have also made them great competitors in stock dog trials, agility events, and other dog sports. Despite their many talents and desirable traits, like many other breeds, the Australian shepherd has developed some inherited disease concerns that can prevent them from performing at their best or otherwise decrease their overall quality of life. One such condition recognized in the Australian shepherd is the genetic eye disease known as collie eye anomaly.
What is CEA?
Collie eye anomaly (CEA), also known as choroidal hypoplasia, is an inherited eye disease caused by a mutation in the canine NHEJ1 gene. Dogs affected with CEA have developmental defects of the choroid, a thin vascular layer of the eye that supplies nutrients and blood to several parts of the eye including the retina and iris. Affected dogs display variable clinical severity from mild choroid thinning without vision deficits to malformation of the optic nerve (coloboma), retinal detachment, intraocular hemorrhage, and blindness. The severity of clinical signs associated with CEA cannot be predicted between generations because mildly affected parents may produce severely affected offspring (and vice versa).
How is CEA Inherited?
Collie eye anomaly is inherited in a recessive manner meaning that dogs must inherit two copies of the associated NHEJ1 gene mutation (one from each parent) in order to develop the disease. Dogs which have inherited a single copy of the mutation are considered carriers of CEA and will not develop the disease themselves. However, carriers are at risk of producing CEA affected offspring if bred with another carrier of the same mutation. Since mildly affected dogs can give birth to severely affected puppies, it is not recommended to breed affected dogs, regardless of their disease severity. It should be noted that some CEA affected dogs display a phenomenon often referred to by breeders as “going normal”. Dogs that have “gone normal” display obvious abnormalities of the choroid and retina on eye exam which appear to resolve at about 12 weeks of age. Though their eyes remain abnormal at the microscopic level, these dogs often do not display vision deficits. Despite their normal appearance after 12 weeks of age, dogs which have “gone normal” should be considered affected when it comes to breeding practices.
Contact Paw Print Genetics
Paw Print Genetics offers genetic testing for collie eye anomaly as well as 9 other inherited diseases of concern in the Australian shepherd. If you have questions about how to eliminate collie eye anomaly from your kennel or have other general canine genetics questions. Please feel free to contact the Paw Print Genetics laboratory at [email protected] or call 509-483-5950 to speak in person with one of our customer-focused, knowledgeable staff members (Mon.- Fri.; 8 am to 5 pm Pacific).
Despite a name which implies an origin “down under”, the Australian shepherd is widely understood to be a breed of American origin. In fact, descriptions of the breed and their importance in the lives of 19th and 20th century Basque shepherds who had relocated from Australia to the western US are plentiful. Australian shepherds’ exceptional intelligence, versatility, desire to please, and a natural instinct to herd and guard livestock have made them a common inhabitant of ranches and farms where they have been trained to perform a variety of tasks. Aside from their work on the homestead, their unique abilities have also made them great competitors in stock dog trials, agility events, and other dog sports. Despite their many talents and desirable traits, like many other breeds, the Australian shepherd has developed some inherited disease concerns that can prevent them from performing at their best or otherwise decrease their overall quality of life. One such condition recognized in the Australian shepherd is the genetic eye disease known as collie eye anomaly.
What is CEA?
Collie eye anomaly (CEA), also known as choroidal hypoplasia, is an inherited eye disease caused by a mutation in the canine NHEJ1 gene. Dogs affected with CEA have developmental defects of the choroid, a thin vascular layer of the eye that supplies nutrients and blood to several parts of the eye including the retina and iris. Affected dogs display variable clinical severity from mild choroid thinning without vision deficits to malformation of the optic nerve (coloboma), retinal detachment, intraocular hemorrhage, and blindness. The severity of clinical signs associated with CEA cannot be predicted between generations because mildly affected parents may produce severely affected offspring (and vice versa).
How is CEA Inherited?
Collie eye anomaly is inherited in a recessive manner meaning that dogs must inherit two copies of the associated NHEJ1 gene mutation (one from each parent) in order to develop the disease. Dogs which have inherited a single copy of the mutation are considered carriers of CEA and will not develop the disease themselves. However, carriers are at risk of producing CEA affected offspring if bred with another carrier of the same mutation. Since mildly affected dogs can give birth to severely affected puppies, it is not recommended to breed affected dogs, regardless of their disease severity. It should be noted that some CEA affected dogs display a phenomenon often referred to by breeders as “going normal”. Dogs that have “gone normal” display obvious abnormalities of the choroid and retina on eye exam which appear to resolve at about 12 weeks of age. Though their eyes remain abnormal at the microscopic level, these dogs often do not display vision deficits. Despite their normal appearance after 12 weeks of age, dogs which have “gone normal” should be considered affected when it comes to breeding practices.
Contact Paw Print Genetics
Paw Print Genetics offers genetic testing for collie eye anomaly as well as 9 other inherited diseases of concern in the Australian shepherd. If you have questions about how to eliminate collie eye anomaly from your kennel or have other general canine genetics questions. Please feel free to contact the Paw Print Genetics laboratory at [email protected] or call 509-483-5950 to speak in person with one of our customer-focused, knowledgeable staff members (Mon.- Fri.; 8 am to 5 pm Pacific).
- Canine Genetic Disease Testing Prior to Other Health Clearances- Why It Makes Sense
- by Casey Carl on Aug. 17, 2015 in All Things Dog , Ask The Vet
As the Associate Medical Director at Paw Print Genetics, I have heard many different strategies employed by our clients to get their dogs’ required or recommended health clearances performed prior to breeding. Some choose to break up their testing over time in order to spread out the cost and many choose one type of health clearance to be performed first with other testing to be completed upon the results of the first round of testing. Based upon the most common testing performed on pure bred dogs, breeders should consider performing their genetic disease testing first, followed by the other clearances they need to pursue before breeding.
Test at Any Age
One advantage to performing genetic health testing first is that it can be performed at any age. Long before the recommended age to complete hip and elbow health clearances via radiography (typically done after 24 months of age), genetic testing results can help with planning your dog’s future. Early identification of undesirable genetic mutations allows breeders and owners to make decisions about breeding and training earlier. In addition, late-onset diseases such as some forms of progressive retinal atrophy (a common cause of canine blindness) or dilated cardiomyopathy (as seen in the Doberman pinscher) may not be identified on veterinary eye or heart exams until closer to the time that dogs begin showing clinical signs. This is true for many inherited eye and heart diseases and is the reason that these clinical exams are often recommended annually. By contrast, genetic testing can definitively identify dogs that are likely to develop the known forms of progressive retinal atrophy or identify dogs that are at significantly increased risk of heart problems due to dilated cardiomyopathy long before these diseases could be diagnosed through a veterinarian.
Whether it means that a promising, future breeding dog ends up as a pet or whether you opt not to make a significant investment in training your dog for hunting, early decisions will save significant time and money. With profit margins being as slim as they are sometimes in the world of dog breeding, early decision making can make the difference between business success and business failure.
More Reliable Results with Less Subjectivity
While it is not true for all genetic diseases, the majority of canine diseases with a known genetic cause (for which testing can be performed) display complete penetrance. Complete penetrance is a term meaning that there is a one to one correlation between the inheritance of a particular genetic mutation and the disease itself; thus meaning that a dog found to be at risk for a particular genetic disease has nearly 100% chance of developing the condition in question (if the dog isn’t already showing clinical signs). For late onset conditions, dogs found to be at risk of these diseases are expected to show clinical signs if they live long enough to develop the disease. Armed with genetic test results on a dam and sire, it is possible to completely avoid producing puppies with these particular inherited diseases by choosing genetically compatible mates. Since one of the goals of canine health clearances is to identify good candidates for breeding, performing testing with more reliable information first, may help a breeder decide earlier how to proceed.
By contrast, the development of diseases with suspected multifactorial causes (such as hip and elbow dysplasia) are not always so predictable for puppies of tested parents, regardless of the parents’ hip or elbow grades. Though hip and elbow grading and selective breeding is likely to help decrease the incidence of dysplasia cases over generations, it is not uncommon for a dysplastic puppy to be born to parents with good or excellent joints on exam. Therefore, making these grading schemes less useful for predicting the health of future puppies than genetic testing results. In addition to decreased predictability of joint disease in puppies, joint grading schemes display some level of subjectivity due to variability between radiologists.
Less Expensive
Another advantage of genetic testing is its relatively low cost in comparison to the combined costs of veterinary exams and radiographs commonly used for health clearances. Though prices for the health clearances performed by veterinarians vary widely by location, in many situations, a complete panel of genetic tests for a particular breed is far less expensive than a single set of elbow and hip radiographs (not to mention the submission fees to grade radiographs and post results to health registries). Although genetic testing cannot provide you the same information you are going to gain from radiographs, a CERF exam, or an echocardiogram, an undesirable result on genetic testing may render further health clearances unnecessary because that particular dog may not be a good candidate for breeding or further training.
The Bottom Line
Despite my proposal to perform genetic testing first, I am in no way stating that other health clearances performed by dog breeders are useless. In fact, these health clearances are an important part of producing healthy dogs and provide health information with a wider focus than that obtained through genetic testing. However, performing genetic testing before other health clearances may save you significant time and money over the long haul from the ability to reliably predict genetic disease risk of a dog’s future puppies and by diagnosing some diseases earlier and at a lower cost than health clearances performed by veterinarians. The bottom line is that performing genetic testing first may be a wise financial choice for your breeding program, especially if undesirable genetic test results are obtained in the process.
If you have questions about how early genetic testing could help your breeding program or if you have general canine genetic questions, please feel free to contact Paw Print Genetics at [email protected] or call our friendly, helpful laboratory staff at 509-483-5950.
Misconceptions About Canine Degenerative Myelopathy
by Casey Carl on June 5, 2015 in Ask The Vet If there is anything that I have learned in Paw Print Genetics’ quest to prevent canine inherited diseases, it is that degenerative myelopathy (DM) is one of the most misunderstood diseases in the dog breeding community. This late-onset, progressive neurological disease is notorious for cutting affected dog’s lives short and preventing them from living out their golden years. Unfortunately, sometimes there are misunderstandings in regard to what causes DM, what DM genetic test results mean, and whether or not DM occurs in certain breeds or bloodlines. I will attempt to address the confusing aspects of DM in order to empower people to eliminate this devastating disease from their blood lines.
How Do DM Affected Dogs Present? How is it Inherited?
Dogs affected with DM typically begin showing signs of painless, hind limb weakness and loss of balance around 7 to 10 years of age. These dogs often have difficulty rising after lying down, will drag their hind feet while walking, and abnormally cross their legs while standing. As the disease progresses, affected dogs’ front limbs also become progressively weaker until the dog becomes unable to walk. Affected dogs also may develop urinary and fecal incontinence as the disease progresses. Most dogs are euthanized within 6 months to 2 years of the initial clinical signs due to poor quality of life.
Though it is no longer the only known mutation responsible for causing DM in the dog, the vast majority of DM cases are caused by a particular reported mutation in the canine SOD1 gene (another mutation, discussed below, has been identified to cause DM in the Bernese mountain dog). Though only described in 5 dog breeds in the initial publication, the same mutation has since been identified in over 100 different breeds. DM caused by this mutation is inherited in a recessive fashion with incomplete penetrance meaning that a dog must inherit two copies of the mutation (one from each parent) in order to develop DM. However, not all dogs that inherit two copies of the mutation will become affected. Dogs inheriting a single copy are considered carriers of DM and will not typically show signs of the disease, but can have affected puppies if bred with another carrier of the same mutation.
Interestingly, DM is the canine equivalent of Lou Gehrig’s disease (amyotrophic lateral sclerosis). In fact, at least one documented cause of Lou Gehrig’s disease is a mutation in the human SOD1 gene.
Breed or Bloodline Susceptibility to DM
Out of all of the misconceptions I have heard regarding DM, the most common one is that DM does not occur in a particular breed or bloodline despite the presence of the common SOD1 mutation in the breed. It is true that some dogs do not ever develop DM even when inheriting two copies of the mutation. This indicates to us that in some dogs, other genetic or environmental factors may play a role in producing a protective effect or slowing the progression of disease such that the disease does not clinically manifest during the dog’s lifetime. However, the factors producing a protective effect are not known and therefore cannot be manipulated to prevent disease in future litters. Since dogs inheriting two copies of the disease can have clinically affected puppies even if they never show signs of the disease themselves, the only predictable way to prevent DM caused by the most common mutation is to genetically test breeding dogs and to selectively breed carriers to dogs that did not inherit the same mutation.
In addition to the issues related to incomplete penetrance of DM, my experiences in clinical veterinary practice made it apparent to me that people may not be aware of DM issues in their line. It was my experience that most owners of DM affected dogs never considered the fact that their dog may be suffering from an inherited issue. Instead, the signs of DM were often written off as arthritis, hip dysplasia, or simply “slowing down” due to age. Without an accurate diagnosis or veterinary discussion of genetics, few owners would feel compelled to contact the breeder of their dog, given that they still knew how to contact them after the 7 to 10 years it normally takes for affected dogs to begin showing clinical signs. Without this vital information from owners, breeders could easily be in the dark when it comes to this condition in their line.
Genetic Testing for DM
Another misconception about testing for DM is that people think that the current genetic testing available for the disease is not useful. While there are probably many reasons why this misconception exists, in addition to the issues related to incomplete penetrance, there are other complexities of DM that likely confuse people.
One troubling finding for some is that a small portion of DM affected dogs will not have the common SOD1 mutation or only possess a single copy of the mutation when tested. The most likely explanation for this phenomenon is that there are other, unknown genetic mutations that are also responsible for causing this disease. If only testing for a single mutation, you may not know what other genetic mutations could be contributing to the condition. While it would likely make sense to most that a dog inheriting two copies of an unknown mutation could cause DM (and not show up on our current DM test) I have found that many people have a difficult time understanding how a dog could inherit a single copy of the common mutation, but still develop the disease. Let’s examine the case of the Bernese mountain dog to help us understand what could potentially be happening in these cases.
In a 2013 case study, a DM affected Bernese mountain dog was described to have inherited a single copy of the most common SOD1 mutation from one parent and a single copy of the Bernese SOD1 mutation from its other parent. Since this dog received a mutated copy of the SOD1 gene from each parent, it did not receive a normal copy of the gene to mask the effects of either mutation as in most recessively inherited conditions. This phenomenon, known as compound heterozygosity is well documented in humans. However, to my knowledge, the 2013 case report is currently the only one of its type in dogs. With discovery of additional disease associated mutations in dogs, it is likely that many similar examples will be found in our canine friends.
Despite the fact that there are likely other unknown mutations responsible for DM in our dogs, the originally described SOD1 mutation is believed to cause the VAST MAJORITY of cases. Given this knowledge, genetic testing and selective breeding could completely eliminate degenerative myelopathy in most blood lines. Thus, justifying the use of the currently available genetic test for DM, despite its limitations.
Contact Paw Print Genetics
Paw Print Genetics offers DM testing in over 100 breeds of dog. To see if your dog breed is potentially at risk, click here. If you have questions about how you can prevent this genetic disease in your kennel or have any other general canine genetics questions, please email Paw Print Genetics at [email protected] or call the Paw Print Genetics laboratory at 509-483-5950.
by Casey Carl on June 5, 2015 in Ask The Vet If there is anything that I have learned in Paw Print Genetics’ quest to prevent canine inherited diseases, it is that degenerative myelopathy (DM) is one of the most misunderstood diseases in the dog breeding community. This late-onset, progressive neurological disease is notorious for cutting affected dog’s lives short and preventing them from living out their golden years. Unfortunately, sometimes there are misunderstandings in regard to what causes DM, what DM genetic test results mean, and whether or not DM occurs in certain breeds or bloodlines. I will attempt to address the confusing aspects of DM in order to empower people to eliminate this devastating disease from their blood lines.
How Do DM Affected Dogs Present? How is it Inherited?
Dogs affected with DM typically begin showing signs of painless, hind limb weakness and loss of balance around 7 to 10 years of age. These dogs often have difficulty rising after lying down, will drag their hind feet while walking, and abnormally cross their legs while standing. As the disease progresses, affected dogs’ front limbs also become progressively weaker until the dog becomes unable to walk. Affected dogs also may develop urinary and fecal incontinence as the disease progresses. Most dogs are euthanized within 6 months to 2 years of the initial clinical signs due to poor quality of life.
Though it is no longer the only known mutation responsible for causing DM in the dog, the vast majority of DM cases are caused by a particular reported mutation in the canine SOD1 gene (another mutation, discussed below, has been identified to cause DM in the Bernese mountain dog). Though only described in 5 dog breeds in the initial publication, the same mutation has since been identified in over 100 different breeds. DM caused by this mutation is inherited in a recessive fashion with incomplete penetrance meaning that a dog must inherit two copies of the mutation (one from each parent) in order to develop DM. However, not all dogs that inherit two copies of the mutation will become affected. Dogs inheriting a single copy are considered carriers of DM and will not typically show signs of the disease, but can have affected puppies if bred with another carrier of the same mutation.
Interestingly, DM is the canine equivalent of Lou Gehrig’s disease (amyotrophic lateral sclerosis). In fact, at least one documented cause of Lou Gehrig’s disease is a mutation in the human SOD1 gene.
Breed or Bloodline Susceptibility to DM
Out of all of the misconceptions I have heard regarding DM, the most common one is that DM does not occur in a particular breed or bloodline despite the presence of the common SOD1 mutation in the breed. It is true that some dogs do not ever develop DM even when inheriting two copies of the mutation. This indicates to us that in some dogs, other genetic or environmental factors may play a role in producing a protective effect or slowing the progression of disease such that the disease does not clinically manifest during the dog’s lifetime. However, the factors producing a protective effect are not known and therefore cannot be manipulated to prevent disease in future litters. Since dogs inheriting two copies of the disease can have clinically affected puppies even if they never show signs of the disease themselves, the only predictable way to prevent DM caused by the most common mutation is to genetically test breeding dogs and to selectively breed carriers to dogs that did not inherit the same mutation.
In addition to the issues related to incomplete penetrance of DM, my experiences in clinical veterinary practice made it apparent to me that people may not be aware of DM issues in their line. It was my experience that most owners of DM affected dogs never considered the fact that their dog may be suffering from an inherited issue. Instead, the signs of DM were often written off as arthritis, hip dysplasia, or simply “slowing down” due to age. Without an accurate diagnosis or veterinary discussion of genetics, few owners would feel compelled to contact the breeder of their dog, given that they still knew how to contact them after the 7 to 10 years it normally takes for affected dogs to begin showing clinical signs. Without this vital information from owners, breeders could easily be in the dark when it comes to this condition in their line.
Genetic Testing for DM
Another misconception about testing for DM is that people think that the current genetic testing available for the disease is not useful. While there are probably many reasons why this misconception exists, in addition to the issues related to incomplete penetrance, there are other complexities of DM that likely confuse people.
One troubling finding for some is that a small portion of DM affected dogs will not have the common SOD1 mutation or only possess a single copy of the mutation when tested. The most likely explanation for this phenomenon is that there are other, unknown genetic mutations that are also responsible for causing this disease. If only testing for a single mutation, you may not know what other genetic mutations could be contributing to the condition. While it would likely make sense to most that a dog inheriting two copies of an unknown mutation could cause DM (and not show up on our current DM test) I have found that many people have a difficult time understanding how a dog could inherit a single copy of the common mutation, but still develop the disease. Let’s examine the case of the Bernese mountain dog to help us understand what could potentially be happening in these cases.
In a 2013 case study, a DM affected Bernese mountain dog was described to have inherited a single copy of the most common SOD1 mutation from one parent and a single copy of the Bernese SOD1 mutation from its other parent. Since this dog received a mutated copy of the SOD1 gene from each parent, it did not receive a normal copy of the gene to mask the effects of either mutation as in most recessively inherited conditions. This phenomenon, known as compound heterozygosity is well documented in humans. However, to my knowledge, the 2013 case report is currently the only one of its type in dogs. With discovery of additional disease associated mutations in dogs, it is likely that many similar examples will be found in our canine friends.
Despite the fact that there are likely other unknown mutations responsible for DM in our dogs, the originally described SOD1 mutation is believed to cause the VAST MAJORITY of cases. Given this knowledge, genetic testing and selective breeding could completely eliminate degenerative myelopathy in most blood lines. Thus, justifying the use of the currently available genetic test for DM, despite its limitations.
Contact Paw Print Genetics
Paw Print Genetics offers DM testing in over 100 breeds of dog. To see if your dog breed is potentially at risk, click here. If you have questions about how you can prevent this genetic disease in your kennel or have any other general canine genetics questions, please email Paw Print Genetics at [email protected] or call the Paw Print Genetics laboratory at 509-483-5950.
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Group:
Herding
Recognition:
MASCA, NAMASCUSA, NSDR, APRI, ASDR, DRA and now accepted into the AKC as a Miniature American Shepherd
Herding
Recognition:
MASCA, NAMASCUSA, NSDR, APRI, ASDR, DRA and now accepted into the AKC as a Miniature American Shepherd