Author archives: Casey Carl

The Veterinarian’s Corner: Variable Disease Presentation and How Genetic Testing Can Help

The Veterinarian’s Corner: Variable Disease Presentation and How Genetic Testing Can Help

Every veterinarian leaves veterinary school with a mental laundry list of animal diseases and their textbook presentations. While this knowledge serves the young graduate well in most circumstances, with clinical experience and mentorship comes the ability for veterinarians to expand their mental notes about the various ways some diseases can present in the real world. For some inherited canine diseases, genetic testing has allowed the practitioner to correlate a broader set of clinical signs for dogs affected by identical underlying genetic mutations. This variability in disease phenotype, known as variable expressivity, is a result of the combined effect of all genetic and environmental factors influencing each individual and can add significant challenge to some diagnoses. However, supplementing a disease workup with genetic test results can prove invaluable in diagnosing inherited diseases that have the frustrating attribute of rarely presenting the same way twice.

Collie Eye Anomaly

Now known to occur in well over a dozen breeds, the recessively inherited collie eye anomaly or CEA (also known as choroidal hypoplasia) is a relatively common eye disease of dogs and a good example of a disorder which can have diagnostic challenges due to its phenotypic variability. CEA is caused by a deletion ...

The Veterinarian’s Corner: Genetic Heterogeneity and Its Importance in Dog Breeding

The Veterinarian’s Corner: Genetic Heterogeneity and Its Importance in Dog Breeding

The discovery of various disease-associated genetic mutations has greatly changed the way some inherited canine diseases are categorized and perceived by the veterinary community. Through the use of genetic testing developed to identify these discovered mutations, various diseases which were once assumed to have a single underlying molecular cause (due to similarity between disease states) have been found in some cases to actually be caused by many different mutations, often in different genes. This phenomenon, known as genetic heterogeneity, elucidates the way genes work together in pathways and how a disruption in different genes of a pathway may result in similar or nearly identical disease states despite seemingly disparate underlying molecular etiologies. Understanding that there may be one of many different genetic mutations responsible for a dog’s clinical signs can help plot a better course for veterinarians to obtain an accurate, definitive diagnosis and in some cases, may alter treatment strategies.

Pet Owner vs Breeder

The accuracy and specificity of an inherited disease diagnosis are particularly important in the world of dog breeding where every potential health issue must be considered prior to breeding. Unlike general pet owners who may not need to know the specific underlying molecular mechanisms of ...

Merle Coat Color- What Veterinarians Should Know

Merle Coat Color- What Veterinarians Should Know

While advancements in science, medicine, and agriculture have played a role in decreasing the relative importance of the dog in human survival, their importance as pets, companions, and surrogate family members may be greater than ever. Once more commonly selected for their athletic prowess and behavioral traits, the rise of dog fancying over the past 250 years has elevated the importance of canine aesthetics to previously unprecedented heights. As a result, dog breeders have historically gone to great lengths to produce dogs with unique phenotypic characteristics desirable to potential pet buyers. While most of these characteristics are simple, mendelian genetic traits without health concerns, some desirable and interesting traits such as the merle coat color pattern are unique to domestic animals and bring with them a complexity and potential health concerns that veterinarians should be aware of in their goal of facilitating canine health and wellbeing. 

An Interesting Mutation for an Interesting Haircoat

In 2006, Dr. Leigh Anne Clark and others identified a semi-dominant genetic mutation responsible for the merle coat color pattern commonly seen in numerous dog breeds including the Australian shepherd, collie, border collie, and dachshund. Merle coat color is marked by areas of normal, eumelanistic pigmentation ...

Canine Genetic Disease Testing Prior to Other Health Clearances- Why It Makes Sense

Canine Genetic Disease Testing Prior to Other Health Clearances- Why It Makes Sense

Once only a dream for dog lovers, technological advances in the sciences have now made testing for certain inherited diseases a mainstay of modern dog breeding. With knowledge of specific, disease-associated genetic mutations and an understanding of how these diseases are inherited, tests can be developed to identify dams and sires at risk of producing affected puppies. With this knowledge, informed decisions can be made in selecting mates which can safely be bred together.

As the Associate Medical Director at Paw Print Genetics, I have heard many different strategies employed by our clients to get required or recommended health clearances performed on their dogs prior to breeding. Some choose to break up the testing over time 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. For a variety of reasons, I propose that performing genetic testing on breeding dogs prior to other health clearances is a practical option that may be in the best interest for many breeders.

Test at Any Age

One advantage to performing genetic health testing prior to other clearances is that genetic testing ...

Who To Test? - Canine Autosomal Recessive Genetic Diseases

Who To Test? - Canine Autosomal Recessive Genetic Diseases

Genetics play an enormous role in the health of dogs walking through the doors of any veterinary hospital. However, the treatment of an animal with an inherited disease rather than proactive testing of the genetic mutations responsible for disease has been the traditional role of the veterinarian. With an increase in the availability of canine genetic disease testing and great improvements in the ease and convenience of ordering genetic testing through Paw Print Genetics, more and more dog breeders and their clients are having genetic testing performed preemptively and learning the benefits of these powerful technologies. As a veterinarian, understanding the basics of genetic testing and how genetic test results can be used to prevent and diagnose disease will keep you current and prepared for your clients as these technologies inevitably become a more significant part of clinical veterinary practice.

One of the more challenging but important aspects of canine genetic testing is deciding what recommendations to make when a dog or one of its relatives are found to be at risk for (or affected with) an inherited disease. Appropriate testing recommendations for the relatives of affected dogs may be crucial for prevention of additional affected puppies and identification of ...

Keep Breed-Specific Thinking from Delaying Your Diagnosis

Keep Breed-Specific Thinking from Delaying Your Diagnosis

Discovery of disease-associated, canine genetic mutations has greatly increased over the past two decades. As a result, identification of these mutations through genetic testing has quickly become a useful tool for dog kennels and veterinary practices by allowing for the identification of asymptomatic disease carriers, diagnosis of affected dogs, and prevention of inherited diseases through informed breeding practices. However, because mutation discovery is often funded by specific breed clubs with interest in a breed-related disease concern, study investigators may not perform extensive, species-wide population studies for a newly discovered mutation. Therefore, in many cases, additional breeds inheriting the same mutation (and developing the same disease) may remain unknown for quite some time after the initial discovery.

As any modern veterinarian can attest, for better or worse, animal lovers have more veterinary medical information at their fingertips than ever before. Occasionally, at Paw Print Genetics, we are contacted by breeders or owners whose veterinarian had opted not to pursue a diagnosis that the client suspected because of the veterinarian’s historical understanding of a disease’s breed-specific distribution rather than the current knowledge. For veterinarians building a differential diagnosis list, keeping the mind open to a particular inherited disease manifesting in an unexpected ...

If a cavalier King Charles spaniel falls in the woods and no one’s around, is it episodic falling syndrome?

If a cavalier King Charles spaniel falls in the woods and no one’s around, is it episodic falling syndrome?

There aren’t many things sweeter in life than a cavalier King Charles spaniel (CKCS). From their friendly, outgoing demeanor to their adorable, pouty eyes, they have definitely become one of my favorite breeds over the years. It appears that others understand my enthusiasm for the breed as well. In the fifteen years from 2002 to 2017, CKCS have moved up from 40th place to 19th place on the AKC’s registration statistics and are one of the most popular breeds in the United Kingdom. Unfortunately, like other popular dog breeds, cavaliers have their share of inherited diseases that can potentially reduce their quality and quantity of life. At Paw Print Genetics, we strive to control these diseases for our canine companions.

One interesting yet, debilitating disease unique to the CKCS is an inherited neurological condition first reported in 19831, known as episodic falling syndrome (EFS). Affected dogs begin showing signs of spastic muscle contractions of the limbs and trunk between 14 weeks and 4 years of age particularly during exertion, excitement, or frustration. As an episode starts, affected dogs most commonly develop rigid hind limb extension, a convex bending of the spine (“roach backed”), and hold their head near the floor ...

Breeding Carriers of Canine Recessive Diseases- Why It Should be Considered

Breeding Carriers of Canine Recessive Diseases- Why It Should be Considered

The breeding of dogs identified as genetic carriers of recessive disease is a hotly debated topic in the canine breeding world with many breeders firmly entrenched in their own personal approach to the issue. With increasing regularity, dog breeders and their clients are bringing genetic questions (including those about breeding carriers) to their veterinarians under the assumption that most veterinarians would be up to speed on the current information and genetic testing available. Unfortunately, at Paw Print Genetics we occasionally speak to breeders whose veterinarians have given them advice about breeding carriers that may not be in the best interest of the kennel or the breed. Given the large number of variables and differences between the way kennels are operated and the recessive disease risks of individual breeds, there is not necessarily a breeding approach that would be appropriate in 100% of cases. However, understanding some guiding principles and the potential ramifications of doing so, can help a veterinarian advise their dog breeding clients in a way that will help them meet their goals without increasing the incidence of recessive diseases in a kennel or in the breed.

What is a “Carrier” of a Recessive disease?

As a quick refresher ...

Nature Versus Nurture- The Case of the All-Male Litter

Nature Versus Nurture- The Case of the All-Male Litter

The often-debated biological argument of “nature versus nurture” is at the center of the challenging considerations dog breeders must make in their effort to produce the healthiest, happiest, and most beautiful dogs they can. Breeders routinely contact the veterinarians or geneticists at Paw Print Genetics (PPG) looking for genetic testing to identify dogs that may be at risk of producing puppies with certain diseases. Given the emotional, temporal, and monetary damages associated with being forced to remove a dog from a breeding program, it is important for breeders to understand whether the disease in question appears to be inherited or whether there might be a more likely environmental explanation for what they see in their blood line. However, when no genetic testing is available for a particular condition, the answer to the question of nature versus nurture may not be quite as straight forward as it may seem at first glance. Keeping your mind open to environmental factors associated with disease might prevent your clients from having to remove their prized breeding dog from their gene pool.

An All-Male Litter?

As a veterinarian, one of the great joys of helping improve the genetic health of dog kennels are the many ...

Canine Genetics in Practice- Congenital and Early-onset Inherited Diseases

Canine Genetics in Practice- Congenital and Early-onset Inherited Diseases

Some of the most emotionally challenging canine cases seen in the veterinary hospital are those involving serious illnesses of newborns or young puppies. Owners’ joyous expectations of a long, healthy relationship with their new puppy makes a disease which decreases that puppy’s quality of life or results in early euthanasia, all the more heartbreaking. Though infectious diseases like parvovirus are often of particular concern in young pups, some puppies ending up on the exam room table show signs of one of a wide array of inherited diseases caused by a known genetic mutation. Unfortunately, limitations in available therapies for many inherited diseases often lead to frustrating and emotional outcomes for all the parties involved; veterinarians and veterinary staff included. Thereby, making prevention of inherited disease through the use genetic testing, an essential part of healthy dog breeding.

Historically, methods to prevent inherited diseases have been limited to selective breeding practices. However, an inability to identify asymptomatic carriers of recessively inherited diseases or dogs in the preclinical phase of late-onset inherited diseases, have traditionally made great reductions in disease incidence difficult to obtain through selective breeding alone. Genetic testing is now playing an important role in identifying these dogs such that ...