Re: RC: CIDs

[CMKSAGEHIL@aol.com]

In a message dated 7/14/99 8:56:30 AM Pacific Daylight Time, 
Linda_Merims@ne.3com.com writes:

<< What is the history of CIDs in Arabs? >>

SCID has apparently been in Arabs since as far back as we know.  It certainly 
isn't a "new" thing--the only thing new is the ability to do a genetic test 
to detect horses that are carriers.  It was at one time thought that the 
carrier incidence might be as high as 25%, but from what I understand now, 
the geneticists feel that the incidence is much less.

<<My breed is Morgans, not Arabs, but I have some dim
recollection that not everybody in the Arab world shared
Lif's outlook.  In fact, I kind of thought the discovery of
CIDs in Arabs created a huge storm of controversy and a
knock-down, drag-out, blood all-over-the-place fight within
the breed over whether CIDs carriers should be allowed to be
registered at all.>>

Originally, when the condition was first identified and the mode of 
inheritance figured out, there WAS a big furor within the ranks of breeders, 
but for the most part, rationality and knowledge of modes of inheritance have 
taken over, and it is now better understood as a disease that can be avoided 
altogether with genetic testing.

<< It was a lot like the Impressive Syndrome
problem in Quarter Horses.>>

Not hardly!  HYPP in Quarter Horses is not a recessive!  Instead, it is a 
condition in which the genes can have an additive effect--i.e. the 
heterozygote is often affected with the problem, and a horse carrying two 
copies of the gene (the homozygote) is usually affected worse.  On the 
contrary, the heterozygote SCID horse is COMPLETELY CLINICALLY NORMAL.  Big 
difference!  I personally would rather have a breeding animal that is 
conformationally correct, metabolically tough, athletic, kind, etc., and is a 
SCID carrier than I would want to trade any of the above traits for a clear 
SCID test.  Don't get me wrong--I think it is wonderful to strive for less 
SCID carriers in the breed.  But meanwhile, education is the key, and as long 
as breeders are aware of the problem and test for it, and make their breeding 
decisions accordingly, then there need never be another foal afflicted with 
SCIDS.  Already they are declining in number with the availability of the 
test.

<<Are Arabs required to be CIDs tested before they can be
registered?  With a positive or negative indication on the
papers?>>

No.

<< As
somebody interested in heirloom mare lines in Morgans, for
instance, one would hate to get in to the position where
the only living descendants of a "clean" mare line now
have the CIDs gene because the last daughter was crossed
with a CIDs stallion who happened to fullfill the 50%
chance to pass on the gene.>>

Unfortunately, it is the "heirlooms" of the Arabian world that seem to have 
the highest incidence, and lord knows that already too many of them have been 
lost to not being the "in" thing in the show ring, etc., etc.  And thanks to 
the genetic test--if the "last daughter" of somebody happens to produce a 
carrier foal, that foal can go on and contribute, provided its mates are 
chosen wisely.

Heidi


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