[pyrnet] Dwarfism

[Kshoffman@aol.com]

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