View Full Version : Breeding Out MV and SM???
4th February 2013, 09:19 PM
We had just taken our 11 mo. old to the vet since she was lethargic and not eating/drinking. Some tests were done and she had a high white cell count. The vet rx'd antibiotics and she was back to normal in a couple of days, but is still taking the rest of the rx. I asked the vet if he knew of Cavaliers getting MV and SM. He said he had seen MV in puppies, but not SM. He said that there was no way to check for SM and asked if Jenny scratched her neck and head. I said yes, probably 2-3 times a day, but our previous dog did too, which he agreed was probabely normal.
From what little I've read, I guess the Cavalier is a relatively new breed that was brought back starting around 1925? I think that I read the breed is even newer in the U.S. from around 1952? Anyway, I guess my question is why have breeders been unsuccessful in breeding out these serious medical conditions and is there any research and or headyway being made now? I'm asking because I have seen a public tv special relating to how dogs came from wolves and a section (in Russia) of the program showing how traits within foxes were changed within just a few generations. Thanks for any info.
5th February 2013, 06:33 AM
It is has to do with how MVD and SM are not just a single recessive gene that gets passed from parents to pups; both disorders are thought to be multifactorial (the same as Hip dysplasia and how two parents rated excellent hips can have offspring with Hip dysplasia) so many genes may be at play and environmental factors as well.
Oh, and if I remember correctly the foxes were only chosen for their friendly nature toward people. The physical appearance that happened is a good example of how several genes are connected to a single trait.
5th February 2013, 06:40 AM
... I asked the vet if he knew of Cavaliers getting MV and SM. He said he had seen MV in puppies, but not SM.
MVD (mitral valve disease) in puppies? That would be a rarity, but not unheard of.
... He said that there was no way to check for SM and asked if Jenny scratched her neck and head. I said yes, probably 2-3 times a day, but our previous dog did too, which he agreed was probabely normal.
There is a way to check for SM. It is magnetic resonance imaging (MRI).
... From what little I've read, I guess the Cavalier is a relatively new breed that was brought back starting around 1925? I think that I read the breed is even newer in the U.S. from around 1952?
The cavalier, as a distinct breed, came about in the late 1920s by breeding longer-muzzled English toy spaniels, also known as King Charles spaniels. It was introduced to the US in the late 1940s and early 1950s, by importing cavaliers from the UK. All bloodlines of CKCSs originated in the UK.
... Anyway, I guess my question is why have breeders been unsuccessful in breeding out these serious medical conditions and is there any research and or headyway being made now? I'm asking because I have seen a public tv special relating to how dogs came from wolves and a section (in Russia) of the program showing how traits within foxes were changed within just a few generations. Thanks for any info.
As for MVD, it is a polygenetic, acquired disease, so no single breeding can eliminate it. In the 1990s, an international team of cardiologists and geneticists devised a breeding protocol to eliminate early-onset (before age 5 years) MVD in the breed. It is described at some length at http://www.cavalierhealth.org/mvdprotocol.htm It was introduced to UK breeders in 1996 and to US breeders in 1998. Since then, that breeding protocol has been followed by very few cavalier breeders, and so no progress has been made in reducing the incidence of early-onset MVD in the breed.
As for SM, it is even more complicated than MVD. It is believed to be caused in part by the Chiari-like malformation (CM) which nearly all cavaliers have in the hind end of their skulls. Testing for it -- using MRI -- is much more expensive than the stethoscopic exams for detecting MVD. There is a breeding protocol for SM, although it has been more of a work-in-progress than the MVD breeding protocol. It is discussed at http://cavalierhealth.org/smprotocol.htm However, as with the MVD protocol, few breeders follow it.
So, to answer your question -- "Why have breeders been unsuccessful in breeding out these serious medical conditions?" -- my answer is that most all of them have not bothered to try. Those who have made the effort report some success.
As for research and headway, gene research is on-going, but the end result of that type of research is not expected to be a silver bullet whereby offending genes simply can be plucked from breeding programs with a forceps.
5th February 2013, 05:39 PM
Many thanks for this information. I know what an mri is as I have had a number of them myself for 2 neck surgeries and degenerative disc disease. The vet said they cost $2,000 for a dog here and that's also a 180 mile drive one way.
Too bad about the breeders lack of desire to improve the breed. Of course we already have our dog, but we were thinking about the future. Obviously, I'm not knowledgeable about genetics. I always thought if I ever went back to college, I would like to major in micro biology and branch off into genetics and DNA analysis. My accounting degree isn't helping me with this stuff :).
5th February 2013, 06:39 PM
Is Jenny insured? If not, insure her before you go anywhere near the vet again and before he starts murmuring SM! Otherwise the insurer will consider it 'a pre-existing condition' and refuse to pay. And having a dog with SM can be a very expensive business, since the only sure way of diagnosing it is by MRI scan, and most dogs showing symptoms will need to be on medication for the rest of their lives.
As well as the gene research that Rod mentioned, there is also research into very early development of the skull (the foetal tissue project) which is producing some very interesting signs that there is a mismatch between the skull ceasing to grow and the brain not getting the message, and trying to find out what causes this lack of communication. But a lot of the research at the moment inevitably has to focus on better treatment for the large number of Cavaliers who already have the disease, often accompanied by considerable pain.
Cavaliers as a distinct breed did indeed emerge around 1925, but they derived mainly from the flat-nosed King Charles Spaniels, probably with some Papillon and Cocker Spaniel thrown in. So the SM genes may go back way beyond the development of the Cavalier as such, and it won't be easy to breed away from it, though, as Rod says, there are ways of breeding to reduce the incidence - if only the majority of breeders would do it.
Kate, Oliver and Aled
5th February 2013, 07:11 PM
I always thought if I ever went back to college, I would like to major in micro biology and branch off into genetics and DNA analysis. My accounting degree isn't helping me with this stuff
:lol: Agree, genetics and DNA analysis is such an interesting and fast-expanding area these days.
You got a good bit of detail above. I wonder if your vet was thinking of puppy flow murmurs, rather than MVD (mitral valve disease). As Rod says, MVD is generally a progressive disease and extremely rare in puppies. Unfortunately over a lifetime, it is extremely common in cavaliers, with about half having it already by age 5, and almost all by age 10.
Breeding away from both conditions, both now widespread in cavaliers, is a real challenge BUT significant steps can be taken by proper testing and using breeding protocols. There have been promising results, decreasing age of onset and severity, in using these tools. Unfortunately there is a cadre of breeders who will use the occasional, unfortunate example where dogs that scan well, produce puppies that go on to have SM, as a (baseless) argument that testing and using protocols doesn't matter. I wish they better understood basic genetics to avoid being so misleading! -- there will always be some risk of this happening, and there's never going to be a guarantee of a clear dog, at least not with the tools breedrs have right now. But the point is, the risk of offspring having SM is vastly -- and I do mean, vastly! -- higher when using unscanned parents, or one dog with known SM, or two dogs with SM, and ignoring protocols. In such cases, over half and often over 70% of offspring went on to develop SM. When two SM-clear parents are used, following the breeding protocols, over 70% were clear at time of scanning. These results came from a significant study of 550 cavaliers.
On the board here, we try to get the word out on these conditions and help puppy buyers learn what to ask a breeder, and what a breeder should be doing -- to try and encourage better breeding practice and the survival of a breed we all love. Often people only learn about these things after buying a cavalier but then they are informed and can use that information to help others, raise awareness, and assist if they decide to get another cavalier in future. :D
6th February 2013, 01:14 AM
This has been a good education for me to learn about these important and critical health issues. Thanks so much.
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