Windt im Wald
A Wind in the Woods
Geauga County, Northeast
Ohio since 1995
COPYRIGHT 1997 By MICHAEL
used by permission of Michael Bowling
Author's note: This
piece illustrates the vitality of a new communications medium for it grew
primarily out of Internet discussions of the subject. Special thanks to
Mary Anne Grimmell who planted the seed of "putting into laymen's language"
the potential uses and misuses of the new CID test, along with the positive
impact it will have on breeding farms, large and small, and who assisted
in reviewing the story in draft.
you know about CID has to be re-examined in the light of a single new
fact. It is now possible to know where the CID gene is. This changes
the shape of our world. No CID foals ever need be produced again.
Remember that progeny testing
was previously the only way to know whether
an Arabian horse had the CID gene. One could
wait, and hope the gene did not turn up by accident;
or one could make a systematic effort, and breed
a stallion to known carrier mares, as one prominent
breeder did with an imported horse a few years
ago. (I am not aware that any other stallion
was formally progeny tested, though there may
have been one or two that I missed. Obviously
if any horse had been so tested, and turned
up negative, it would have been trumpeted from
the housetops. Even at the highest estimates
of CID gene frequency, most horses are expected
to be negative; this implies that few were tested.)
To achieve 95% confidence of
knowing an individual Arabian did not have the
gene, one would have to see a) 11 healthy offspring
from known carrier mates; or b) healthy inbred
offspring from 22 of the tested animals's own
offspring. That awkward gender-free sentence
is the only one I am going to have to write,
since obviously no mare could ever be rigorously
progeny tested to be CID-free, and also have
a breeding career as such. Most Arabian stallions
would end up siring more offspring in their
progeny testing phase than they did in their
breeding careers. (Note that breeding a prospective
sire to 22 of his own daughters would have the
advantage, over the 11 offspring from carrier
mares, of potentially turning up any lethal
or seriously deleterious gene(s), not just CID.
Note also that it is 11 offspring from known
carriers--which could include several offspring
from any one carrier--but it is offspring from
22 different daughters.) That testing, to that
level of confidence, has been prohibitively
expensive -- this is plain from the fact that
essentially no one did it. And it would generate
a whole crowd of young horses that needed to
be somewhere, after the testing was done, whether
the results were positive or negative.
CID can be openly discussed,
because acknowledging one individual has the gene will
no longer cast a pall over a whole breeding program
or line of breeding. Individual horses can be tested
and their individual status can be known; matings can
be planned accordingly; guilt by association, and the
notion of contagious genes, can finally be laid to rest.
The rumor mill will have to find something else to grind.
Statements of the form "Our neighbor's daughter's boyfriend's
cousin knew someone who bred a mare to that horse and
had a CID foal" will no longer carry any weight (not
that they should ever have done, but the climate of
ideas will change, and the impossibility of proving
a negative will no longer apply). The delusion that
CID is the only lethal gene of concern in Arabian breeding
can be put out of its misery as well, and the substantive
discussion of other problems, and the search for other
gene tests, can begin -- inspired by the success with
this difficult and challenging problem. The paradigm
has shifted. New ways of thinking will be required.
What are the drawbacks to CID
(or any lethal defect) without a gene test? I submit,
suffer major emotional and financial hardship.
newcomers are put off becoming involved with the
breed: at best they cannot be sure their new horses
are not carriers, and they are at some risk of having
known, but unadmitted, carriers foisted off on them.
What becomes of those drawbacks,
given a carrier test? They all go away:
foals need die, because no one need unknowingly
cross together two horses with the gene.
can test their stock and know how to avoid the problem.
3) Potential buyers
can test their prospects and know where they
stand. The paradigm shifts, and new ways of
thinking are required.
the frequency of a gene in a breed to be reduced, it is not necessary
to remove from breeding all individuals possessing it. Such animals
need only sire or produce fewer offspring than they would have done
under random mating (if their status had not been known, in other words).
That is almost certainly what will happen once this gene test is in
widespread operation, and the gene's frequency in the breed will gradually
decrease. The benefits of the test therefore can be obtained without
gelding all gene-positive colts, or denying registration to all gene-positives,
or any other such scheme; therefore to do so would be an injustice.
It would be applying the test to punish "a moral flaw," rather than
as a tool to manage "a gene" for the benefit of the breed. Genes do
not have moral or ethical content; questions of right and wrong arise
in the way humans deal with their knowledge.
Every individual of every species carries genetic
defects, and CID is not the only lethal operating in the Arabian breed.
Acknowledging the existence of a problem, and developing a rational means
to deal with it, is the opposite of denying that it is a serious one. All
the drawbacks of CID arose out of the fact that we could not tell where
the gene was. Now we can. Vicki Hearne's Adam's Task, a book of long
essays on animal training, describes human-animal interaction as a form
of language. One of Hearne's recurring themes is "the stories we know" about
animals, or about the ways humans interact with animals, or the way animals
interact with humans (she refers to animals as "knowing stories" too). Her
position is that we can operate only in terms of the stories we tell ourselves,
because that is the practical form our knowledge takes.
genetic immuno-deficiencies are a complex set of conditions;
since the early 1950s close to 20 different syndromes
have been reported in humans and examples have been
recorded in a few other species. The first indications
of what came to be recognized as severe combined immunodeficiency
(SCID) of Arabian foals were clinical reports out of
Australia in the 1960s, and the syndrome was described
in the U.S. in 1973. Its inheritance as a simple autosomal
recessive was established by 1977. The disease can be
tentatively diagnosed from a blood sample of a young
foal. A white blood cell (lymphocyte) count of less
than 1000 per mm3 (vs 2500-3000 for a healthy foal)
and lack of IgM (immunoglobulin M) are presumptive evidence
of SCID; confirmation is by post-mortem showing underdeveloped
thymus and lymph nodes. Lacking immune capacity, such
foals will succumb before 5 months of age of massive
the SCID gene test:
Arabian foals of untested parents can be tested
for the presence of the SCID gene in double dose,
which will provide rapid and definite distinction
between foals which are candidates for major supportive
efforts and those which are not.
owners considering outside stallions for prospective
matings can ask to see evidence of SCID gene status,
and make informed breeding decisions.
a breeding program, excellent individuals which
happen to possess the SCID gene may be bred so as
to retain their good qualities and yet avoid producing
affected foals, and gradually reduce the gene's
It should be emphasized
that SCID is a recessive genetic defect; no evidence
has ever been found for any defect or weakness in
This notion has wide applications. For
many years Arabian breeders told themselves the story that the
Arabian, as "the oldest and purest breed of horse," must
by that nature be free of lethal defects. Many of them even
extended this story to say that, if a lethal gene ever appeared,
it must be the result of a pedigree flaw (not in the sense of
introducing a gene from outside, but of somehow "causing" defects
by violating the breed's metaphysical purity). I recently commented
to someone that Arabian horses have been held to be immune to
the laws of biology; their genetic problems are viewed as the
effects of past moral transgressions (this is a prominent theme
in 19th century nature philosophy, and in early 20th century
racism). The story of population genetics now tells us that
lethal genes, like other genes, are part of a breed's and a
species's history. Every individual of every species is now
held to carry some lethal or highly deleterious gene(s) in hidden
form. The longer a species has been under domestication, with
matings controlled by humans and limited by studbook breed definitions,
the more such genes will have a chance to arrive at substantial
frequencies, and therefore to become unhidden through homozygous
expression. In other words, the story that many Arabian breeders
tell themselves, which amounts to saying that CID was a temporary
aberration and if we can only get rid of that gene we will be
"safe" again, is mis- (or dis-) information. There are candidate
lethals described in the genetics or veterinary literature,
some of which are better established than others (in terms of
mode of inheritance, or the simple fact of being inherited;
some are at present merely suspicious, since they appear to
be recurring and breed-specific.).
The success of the CID story is that
the gene now can become unhidden without killing foals. Our
constructive response now is not to obsess over CID, which has
been made harmless. It is to look for modes of inheritance,
and for gene tests, which will put the other problems in the
same position. People have been breeding blind with regard to
CID for decades (its recessive nature has been known for over
20 years, never mind how long it existed before being defined).
Now that situation has changed. With a gene test, CID is going
to become a matter of fact. It will not be a whispers-behind-
the-hand subject as it has been for so long. Some discussions
of this topic seem to assume that the way things are (attitudes
and assumptions, the stories we tell ourselves) are going to
remain the way they are right now, forever. They will not. The
paradigm has shifted. New ways of thinking are not only required,
they are inevitable.
McGuire, T.C. and M.J. Poppie. 1973.
Hypogammaglobulinemia and thymic hypoplasia in horses: A primary combined
immunodeficiency disorder. Infection and Immunity 8: 272-277.
Poppie, M.J. and T.C. McGuire. 1977.
Combined Immunodeficiency in foals of Arabian breeding: evaluation of
mode of inheritance and estimation of prevalence of affected foals and
carrier mares and stallions. J. Amer. Vet. Med. Assoc. 170: 31-33.
Shin, E.K., L.E. Perryman and K.
Meek. 1997. A Kinase-Negative Mutation of DNA-PK (subscript CS) in Equine
SCID Results in Defective Coding and Signal Joint Formation. J. Immunol.
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Studdert, M.J. 1978. Primary, Severe,
Combined Immunodeficiency Disease of Arabian Foals. Austr. Vet. J. 54:
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L.F. Van Dyk, L.E.Perryman and K. Meek. 1995. Equine severe combined
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