Written by Samary Birkline, © 2020
If you’re in the market for a Doberman Pinscher, you might be wondering what all the fuss is about DCM (Dilated Cardiomyopathy). There’s an awful lot of chatter in the breed forums and heart disease is among the leading topics. To simplify this multifaceted conversation, it’s important to understand what we know and what we don’t know about this disease based on science.
Dilated Cardiomyopathy breaks down easily in its definition; dilated (enlarged) cardio (heart) myopathy (muscle suffering). In layman’s terms, it is commonly known as an enlarged heart. It is very prevalent in the beloved Doberman breed. So much so, that some vets have been known to tell their clients to select a different breed if heart disease is a deal breaker. Indeed, some studies estimate that over 58% may become affected in their lifetimes.
But this doesn’t have to be the case. Breeders have a collective opportunity to change the future. We must work together to build a stronger breed.
Symptoms of the disease usually begin in the first two years of life (though sometimes are late onset), and can include:
- Fainting Spells
- Difficulty Breathing
- Fluid Distension of the Abdomen
- Sudden Death (from irregular heart rhythm) without previous symptoms
The treatments for DCM are extensive and can assist the heart in supporting the body and prolong life by several years, but Dilated Cardiomyopathy is, most often, if not always, a fatal disease.
The good news is that scientists have been successful in isolating the genetic markers that have been identified as risk factors for developing the disease. The first marker is called PDK4, specifically associated with Dobermans. It is commonly known as DCM1 in many chat forums and groups. But despite the identification of the gene, it was known there was another risk factor. Dogs who did not have this PDK4 market were becoming affected, so more research was done.
Relatively recently, DCM2 (called TTN) was mapped, and the awareness of its existence is spreading. There is some general disagreement as to the presentation of the markers. Some breeders insist that a dog can test clear one day and the next day, with a different test will show genetic markers. The confusion may be caused by the newer discovery of the second genetic marker. Indeed, breeders have given their dogs what is labeled a “DCM Test” from legitimate laboratories, only to find out with a phone call that the lab only tests for PDK4 and doesn’t even have the capacity to test for TTN. With an alternate test, some breeders are surprised to find out that a dog who had received negative results for the tests described above, now tests positive for [the TTN marker of] DCM.
There is also talk, in the scientific community, about a third genetic marker associated with DCM, because dogs that have had neither genetic marker have developed Dilated Cardiomyopathy. Much more research is needed to map and understand it, and this is, indeed, underway. However, until this marker is isolated, breeders must do their best to slowly eradicate the markers that we DO know from the ranks.
Furthermore, it’s been learned that the genetic markers are dominant, but with incomplete penetrance. This means that some dogs that have one or both markers never show clinical signs of an enlarged heart and that the presence of the marker is said to issue the same amount of risk whether one copy is detected or if two copies of the variant are found. Understandably, all of this in depth can be overwhelming to breeders, with even those with the best of intentions.
The necessity for a scientific understanding of basic genetics isn’t the only thing preventing good breeders from improving their programs. Adding to the complicated nature of the science, some labs deliver their test results in vague, unclear reports, lending to breeder confusion and misconception.
It’s important to understand the genetic markers are a risk factor, and they do not necessarily mean the tested dog will die early or even of heart abnormality. These markers are to DCM what smoking is to lung cancer. Not every smoker will develop cancer, and those who have never smoked may still develop it. There may be other risk factors, some of which are being researched.
The American Kennel Club Canine Health Foundation website states, “There is suspicion that the disease in some dogs is associated with boutique, exotic ingredient, or grain-free (BEG) diets. Some affected dogs on such diets have shown reversal or improvement of their disease after changing their diet, supporting a potential association between consumption of a BEG diet and development of DCM. A specific cause, however, has not been identified, despite extensive nutritional testing of the dog foods and the canine patients. Moreover, the extent of the problem is unknown because only dogs that are symptomatic for DCM have been reported. It is possible that more dogs may be affected but not yet showing signs of heart disease.” Studies are being arranged to dive deeper into this link.
So what is the solution?
Every responsible Doberman owner addresses heart health concerns with a breed-familiar veterinarian, and should, in addition to annual vaccines, cardiac testing should be performed. But, the bigger responsibility lies with breeders. Preservationist breeders are at the heart of this breed, excuse the pun.
At first glance, one might ask, why don’t we just stop breeding the carriers of these genetic markers? We don’t do this because the gene pool for Dobermans is surprisingly small. If breeders avoided breeding every carrier of the DCM1 or DCM2 genetic markers, there would be a COI (coefficient of inbreeding) spike in the breed that would do way more harm than good. Inbreeding and linebreeding are credited with some of the mess we are in with this breed, thus increasing the breed’s COI should be avoided. Leading geneticists agree.
The Kennel Birkline believes that over a few generations, the genetic risk factors for Dilated Cardiomyopathy could be bred out of the breed. We believe that if breeders began to work together instead of facing one another in competition, that we could make a difference in a very short time. Doberman breeders could easily unite in this effort. A successful strategy might go like this:
- Generation 1 (2020): Breeders select temperamentally sound breeding stock, that have the best confirmations, matching non-carriers with heterogeneous carriers
- Breeders invest in Embark testing of the entire litter, selecting only the genetically clear or the absolutely stunning specimens.
- Generation 2 (2023): Breeders deliberately inter-mix their stock with the explicit purpose of creating a new generation of incredible mostly clear pups.
- Breeders again invest in Embark testing of the litters, selecting ONLY the genetically clear AND absolutely stunning Dobermans.
- Generation 3 (2026): Breeders now have genetically clear stock and using pedigree information and DNA analysis, can continue to reduce the COI and the risk of disease in the bloodlines of our favorite breed.
I argue that inside 20 years, a coordinated effort; an assault on DCM could make a real impact on the breed. Certainly there are those who will disagree with this plan, but with each heartbreaking story that comes across our social media pages, The Kennel Birkline becomes more committed to doing our best to clean the breed as best we can. Hope for the future begins with every single breeder doing what we can to first produce homogeneous carriers, then eventually genetically clear stock. We look forward to the future; when DCM is a thing of the past, eliminating the number one killer of Doberman Pinschers.