by Barbara E. Magera, MD
My passion and commitment is to improve the health of the Cavalier breed. Without bragging, my Cavaliers have won many ribbons and accolades in the US and internationally; however, many succumbed at an early age to heart disease. As a physician, I understand the importance of early diagnosis and treatment. Cavaliers, like many other toy breeds, have a high incidence of myxomatous mitral valve disease (MMVD). The consequences are cardiac enlargement, congestive heart failure (CHF) with associated appreciable morbidity and early death. Using present day technology with pedigree knowledge, I offer my approach to evaluate my Cavalier breeding stock and to guide my breeding decisions.
I try to avoid the desire to breed based solely upon the phenotypic traits of a Cavalier. I categorize this approach as “breed blindness”. An example is observing a beautiful Cavalier in the ring and deciding to incorporate that canine into my breeding stock based upon the dog's looks, structure, temperament and show presentation. We see this often with top winning dogs who months later have sired multiple progeny. Of course, everyone wants to own beautiful dogs. The opportunity to own a drop-dead gorgeous puppy with an impeccable pedigree is every breeder’s dream. Conversely, no one wants to own a bunch of ugly dogs. This isn’t the objective of anyone involved in the sport of conformation. No one is going to win titles in the ring with a healthy canine that does not represent the breed standard.
My criteria for breeding may not be acceptable to many Cavalier breeders. I will identify a potential Cavalier that would add a specific trait to my current breeding stock; however, before proceeding any further I want to know the health testing, particularly the cardiac test results of the Dam and Sire. In the case of a dog older than 14 months, I particularly want to know the cardiac status of this bred-potential dog. An Echocardiogram (Echo) is the gold standard to evaluate the valvular status of humans and dogs. A 2D Echo visualizes the mitral valve apparatus and provides quantitative information about chamber size and cardiac function. In my decision process, this information is critically important together with the age of the Cavalier.
I perform routine screening Echos regardless of any auscultatory findings. The presence or absence of a murmur does not provide adequate information for me to access the dog’s cardiac status. Studies have documented that a prolapsing mitral valve and left sided chamber enlargement may be present even if a murmur is not heard by auscultation. By the time a murmur is present, irreversible cardiac damage specifically atrial enlargement, may have already occurred and the progression to CHF has begun.
Recently, my Canine Cardiologist evauated two of my young, male Cavaliers. The week before, I was agonizing over which Cavalier to heart clear for breeding. Both have exceptional color, coat, structure, reach and drive but one has a show-stopping melting facial expression. I mentally visualized which of my heart cleared females I would use for a mating. When I saw both male dog's real time Echo on the screen, my heart sank. Both had a prolapsing valve but also marked left atrial chamber enlargement with values nearly double the normal. Both were immediately started on cardiac medications. I am mentally clear on my decision to eliminate these dogs from my breeding program. My experience with MMVD and these Echo findings indicate that their lifespan could be severely limited. Thankfully, we identified their cardiac problems. They were started on medications known to improve their quality of life and hopefully prolong their life span.
At the same Cardiology visit, we Echoed my 10 year Cavalier who has achieved his conformation Championship in the U.S. and abroad. To my surprise, he is Echo heart cleared. He passed the routine other health clearances currently advocated. Today’s findings clearly influenced my decision to include this older male into my breeding program. Luckily, I banked his sperm collected when he was young. I view collecting and banking sperm as my insurance policy. I do this routinely during the first years my dog is in the show ring.
When evaluting a Cavalier for my breeding program, I routinely request from the breeder Echo results on the Dam and Sire. My experience, particularly with US breeders, is that, for whatever reasons, they are unwilling to perform an Echo despite my offering to pay 50% of the Echo charges. I will not go into the numerous reasons voiced by established Cavalier breeders of why they are reluctant to heart screen their Cavaliers with an Echo. To save everyone a lot of emotional chatter, I am “up front” about anyone who approaches me about buying their Cavalier puppy or those who wish to breed to my Cavaliers. It is nothing personal or judgemental about their ethics or value system. Additionally, I do not wish to justify my position for wanting an Echo over auscultation. I have been labeled with many derogatory terms; however, I am committed towards improving the cardiac health condition of at least my breeding stock. I cannot speak on the behalf of other breeders who also are committed to improve Cavalier health.
MMVD is a very complicated condition. The current approach of US breed clubs is to support efforts to identify the genetic abnormality of MMVD and potentially offer corrective gene therapy. Although this approach is laudable it is not practical or easy. A California based company offers corrective MMVD gene therapy for Cavaliers. Other gene testing labs offer identification for alleles (ie “gene part”) that they state may predict the future occurrence of MMVD.
At the time of publishing this article, the gene therapy project has yet to receive an investigator approval from the FDA. Without the FDA review and approval, this approach remains a research project. Unfortunately, many seek a simple solution to a complicated problem. The result is financial support by breed clubs for unproven projects in the hope of saving the breed from the ravages of MMVD.
The goal of gene therapy is to correct the underlying disease. It is important to note that treatment is available for many common conditions while the exact genetics of the specific disease remains unknown. Some potentially lethal conditions include asthma, diabetes inflammatory bowel disease, autoimmune conditions, sepsis and more. Although genetic research continues, these conditions are effectively managed by understanding the pathways contributing or causing these conditions.
With present gene modifying therapies available for human conditions, a critical question is what is the longevity of the gene therapy. Thus, it is important to report not only the success of the gene therapy to correct the abnormal pathology but to ensure that the benefits are long lasting.
Gene altering therapy including biologics interferes with normal immunity. These therapies also adversely affect other immune processes such as cancer surveillance. Post marketing studies have identified that some of these therapies increase the risk of lymphoma, leukemia, blood dyscrasias and other serious end organ damage.
There is a growing belief that out crossing a Cavalier to another breed may ultimately eliminate or at least minimize the serious medical conditions affecting toy breeds such as the Cavalier. This approach is, at best, experimental and largely advocated by those with little to no training in genetics or veterinary medicine. A more thoughtful approach to improve Cavalier health might be to breed to a healthier Cavalier stock. The routine use of modern proven testing methods together with knowledge of pedigrees provides additional information to guide thoughtful breeding.
As a toy breed, the Cavalier is subject to other medical conditions; however, my focus upon MMVD exists because of its potential lethal consequences particularly in young canines. I offer my opinion to other breeders and fanciers in the hopes of improving Cavalier health and preservation of this lovely breed.
Barbara E. Magera MD, PharmD, MMM (Caracaleeb) is a Cavalier fancier, exhibitor and breeder, photographer and writer who lives and practices medicine in Charleston, SC.
Nikolaus, my US and international Cavalier champion.
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