|Dr. Sunshine M. Lahmers, DVM, PhD, Washington State University, has submitted her findings on the the AKC's Canine Health Foundation (CHF) donor advised grant: Characterizing mitral valve disease in the Norfolk Terrier. Following is a report by Carol Falk with a summary of where we are now and some thoughts on how we need to proceed. ANTA is grateful to all who have participated in this study, but especially to Carol and Nat LaMar who were the driving forces behind the initial effort to unravel the mysteries of MVD in Norfolks.|
In the year 2000, after becoming frustrated with lack of progress in establishing funding for MVD (mitral valve disease) research in the Norfolk Terrier, Nat LaMar and I sent a survey to large numbers of Norfolk owners in the United States, Canada, and several other foreign countries. Using ANTA and NNTC mailing lists, we solicited money and information from concerned owners in hopes of establishing a fund with the AKC Canine Health Foundation (CHF) to study MVD in our small terriers. The response was overwhelming and within a short period of time, we established a Donor Advised Fund (DAF) called "Friends of the Norfolk Terrier" with the CHF.
In addition to raising more than $20,000, it became increasingly evident from Norfolk owners' responses that MVD was a big problem in our breed. In all, 138 breeders/owners responded to our survey, reporting on 502 dogs. Ninety one dogs had been diagnosed with heart murmurs; 52 of these were deceased; 46 of the affected dogs had died of heart failure.
It took me several years, but I finally located Sunshine Lahmers, DVM, PhD, a veterinary cardiologist resident at Washington State University (WSU). She presented a grant, approved by the CHF, to study MVD in the Norfolk Terrier. With the invaluable help of breeders Deborah Pritchard (Glenelg) and Kathleen Eimil (Mayfair) and veterinary cardiologists Luis Braz-Ruivo DVM, ACVIM and Richard Kienle, DVM, ACVIM, we were up and running.
Preliminary ultrasound results from the first part of the study are alarming. Because the study will most likely be published within the next year in a peer reviewed veterinary journal, I am not able to share all the facts and figures at this time. However, more than 60% of the Norfolk Terriers studied showed evidence of mitral regurgitation (leaky mitral valve)!
The following are Dr. Lahmer's conclusions from the first phase of her MVD research:
"The results of this study indicate that the Norfolk Terrier is affected by endocardoisis (degeneration) of the mitral valve. There appears to be a wide distribution of ages affected with two peak time periods, which would suggest the possibility of an early onset form of endocardiosis in the Norfolk. The analysis of a control group of dogs (non-Norfolks) is pending to determine if and to what extent the amount of MVD in the Norfolk exceeds what is seen in the general dog population. The data also reveals that only approximately half of the affected Norfolks will have physical exam abnormalities to indicate the presence of mitral valve endocardiosis, thereby suggesting that echocardiography will be necessary as a screening tool to identify the early stages of this disease."
Since the majority of Norfolks in this study only exhibited a mild form of MVD, "the most significant question raised is how Norfolk Terriers with mitral valve endocardiosis progress. Is it a slowly progressive disease only reaching clinical significance (i.e., becoming symptomatic) in geriatric patients or are Norfolks affected in a manner similar to the Cavalier King Charles Spaniel, characterized by an early onset and rapid progression? Follow-up echocardiography on the dogs in this study and pedigree analysis of entire families would be necessary to answer these questions and to provide further information about the inheritance pattern of this disease."
It is my hope that Dr. Lahmers will be able to continue her research under AKC Grant #0357. The money is available, and we need to pursue necropsy evaluation of affected hearts (none were submitted) and extensive pedigree analysis. According to Dr. Lahmers, initial pedigree evaluation shows that males and females are equally affected and that affected dogs have been seen in each generation, thereby suggesting that MVD is not a sex-linked trait and that a dominant inheritance pattern may be more likely.
We have learned one very important fact from research already completed. Auscultation (listening to the heart with a stethoscope) is not a sufficient screening method for the Norfolk Terrier. Breeding stock should have an echocardiogram in order to be certified free from MVD. Although at the present time, OFA will issue a heart clearance to a Norfolk based solely on auscultation, this can no longer be the recommendation of the NNTC. (Ed. Note: Carol and Lori Pelletier also recommended echociardiography at ANTA's 2005 Fall Festival.) According to Dr. Lahmers, Norfolks to be used for breeding who have "normal physical exam findings should be examined by echocardiography to identify `silent' mitral valve disease."
We are hopeful that the CHF will extend the grant for MVD research for at least another year. As mentioned above, the second phase of the study would involve necropsy evaluation of dogs' hearts affected by MVD as well as extensive analysis of Norfolk family pedigrees.
Funding for phase two is available from our "Friends of Norfolk
Terrier" DAF. Dr. Lahmers has indicated her interest in continuing
the study, and I hope that the two veterinary cardiologists Dr. Luis Braz-Ruivo
and Dr. Richard Kienle will also stay on board. There will be a brief hiatus
in the project, however, as Dr. Lahmers will be on leave from WSU from October,
2006 until June, 2007. Happily, she and her husband are expecting
their first child this fall. Along with maternal responsibilities, she also needs time to study for her board cardiology exams. We will be back in touch with ANTA and NNTC members in the near future about submitting pedigrees and their deceased dogs' hearts in an effort to increase our understanding of this killer disease.
Carol Falk, NNTC Health & Genetics Chairman, Co-Founder "Friends
of Norfolk Terriers" DAF (email@example.com)
ANTIC, September, 2006
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