Re: [pyrnet] Dwarfism

[Jack & Charlotte Perry <pyreau@erols.com>]

I agree, Kelly, that epilepsy, heart disease and luxating patella are very
worrisome and in some ways perhaps more serious.  Still, I would hate to think
of  people deliberately breeding for dwarf Pyrs.  Also if this is a recessive
gene and every time a carrier is bred 50% of the offspring are carriers, we could
end up with a lot of carriers in a short period of time.  We could get to the
point where it would be difficult to find a dog that was not a carrier.  This is
a good reason to make every effort to determine some sort of marker.
Charlotte

Kshoffman@aol.com wrote:

> Interesting reading everyone's thought on dwarfism, and it's potential threat
> to the breed.
>
> I admit to having some doubt about it being a simple recessive, although I
> certainly hope for our breed's sake it is.  If we are dealing with a simple
> recessive, and if we can create an environment where folks could just feel
> comfortable casually divulging the information on known carriers as plain and
> simple data to anyone who might have a need to know, we can pretty easily
> work around this problem on a population level, IMO.
>
> I seriously doubt we will ever totally eliminate it, so I have put that
> thought out of my mind.  I tend to think in terms of how can we control it,
> how can we potentially (slowly if necessary) reduce the frequency of
> affecteds and the carrier rate. Dwarfism just doesn't get me too worked up.
> I've found it easy enough to avoid and I think there are much worse things
> one could produce in a breeding program.
>
> When I first got involved in this breed, began to build my foundation and
> plan a breeding program, the lines that I chose to work with were rumored to
> be "dwarf lines".  The way I heard things, based on my pedigrees, I could
> have expected to get dwarfs in every litter.  But guess what?  I did not.  In
> a total of 15 litters bred or co-bred over the past 10+ years, intensely
> linebred on pedigrees rumored to be littered with dwarf carriers, we've seen
> one unofficial dwarf.  One, out of all those puppies.  I say "unofficial"
> dwarf because in her case, radiographs did not confirm the diagnosis, but I
> consider her to be a dwarf based on her size and proportions.  She is ~30-35
> pounds, ~12-13 inches at the shoulder.  While she is out of proportion, legs
> to body, head, and tail, she does not have twisted or bowed limbs, at least
> according to her owner/co-breeder.  She is a healthy happy dog, but her owner
> describes her as "hard of hearing".  That is the only health issue she has,
> aside from her abnormal, small stature. I'm not saying I take this lightly,
> nor that I think it's okay, just that in my opinion there are worse things to
> worry about, in addition to worrying about dwarfism. If anyone wants the
> pedigree, email me privately and I will give it to you, but keep in mind, she
> was not officially diagnosed as a dwarf.
>
> I feel quite confident that I can pretty effectively and responsibly deal
> with dwarfism, even without throwing the baby out with the bathwater.  Now,
> if you want to talk epilepsy, that gets me pretty concerned and worked up.
> I'll take a dwarf over a cluster-seizuring dog any day of the week.  In at
> least two breeds I am aware of, Belgian Shepherds and Miniature Schnauzers,
> the mode of inheritance of epilepsy is believed to be a polygenic (multiple
> gene) threshold model, also environmentally mediated.  IOW, a multifactorial
> mode of inheritance, which in my mind are THE MOST DIFFICULT types of genetic
> health defects to control.  There is plenty of reason (to my way of thinking)
> to believe this is the case in other breeds with epilepsy as well.
>
> In Belgian Shepherds, the rate of affected with epilepsy is in the 15-18%
> range.  Considering the fact our researchers in Belgian Shepherds (allegedly
> close to having a linked-marker test) hypothesize a three-gene threshold
> model, I can only imagine what our "carrier" rate is. ("Carrier" is actually
> a misnomer in this scenario.)  It is entirely probable that a good 90+% of
> all Belgian Shepherds are capable of producing epilepsy when bred to the
> "wrong" mate.  THAT worries me.  I really do not want to see Great Pyrenees
> go there.
>
> Here we sit on the dwarfism thing, basically having only pedigree risk
> analysis to go by at this point (which I find pretty effective, personally)
> waiting for a possible linked marker test, which could be years down the road
> IF it happens at all, when we could quite possibly be making great inroads in
> reducing the frequency of dwarfism in the breed simply by sharing data.  If
> folks could just feel more free to casually share and exchange data publicly
> without fear of recrimination, I believe it would go a long way.  Many of us
> already do this, privately, which is why we probably feel we have a decent
> handle on the dwarfism thing.  But, I feel somehow it needs to go beyond the
> private need to know basis, because obviously the necessary data isn't always
> filtering it's way down to ALL who have a need to know.
>
> Suggesting or even thinking that all or even most *potential* carriers of
> dwarfism (those descended from known carriers, but whose status with regard
> to being a carrier themselves is unknown) should be eliminated from the gene
> pool is foolhardy, IMVHO.  Consider this:  If there truly was some push or
> broadly embraced recommendation to dramatically reduce or eliminate
> *potential* dwarf carriers from the gene pool, and the masses heeded that
> call, you'd better believe we would see a rapid and perhaps gravely
> concerning and dramatic increase in any number of other equally or MORE
> concerning and debilitating health defects that are much harder to control.
> Take your pick: hip dysplasia, patellar luxation, epilepsy, and undoubtedly a
> few more.
>
> To me, dwarfism at this point in time seems comparatively easy to avoid and
> control.  Let's not lose sight of that fact and forget about some of these
> other issues that also are a threat to our breed.
>
> Kelley Hoffman
> kshoffman@aol.com
>
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