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SCID
(Severe Combined ImmunoDeficiency) is a lethal genetic disease of Arabian
foals inherited as an autosomal recessive (meaning it is not sex-linked,
and requires a copy of the gene from each parent to manifest. A carrier
horse will transmit the gene to its offspring only 50% of the time, so
half its foals will be SCID-clear. If two carriers are bred together,
there will be a 25% chance the foal will inherit two copies of the gene
and die, a 50% chance it will inherit only one copy and thus be a carrier,
and a 25% chance it inherit no copies and thus be SCID-clear.)
Lacking a competent immune system, foals with two copies of the gene succumb
before five months of age to massive infection, primarily of the respiratory
tract, so they normally die of pneumonia. An affected foal provides evidence
of carrier status of both parents. Estimates run from 8% to as high as
25% of the Arabian population carries this gene, and instances of it have
now been indentified in all bloodline groups. Fortunately, a DNA test
is now available, so no foals ever need die this way again, simply by
avoiding breeding two carriers together. The least expensive vetgen tests
are available at www.foal.org for $99.
The swab method can be done by horse's owner/handler and does not need
a vet. They have also started taking hair samples in conjunction with
the cheek swabs, and if the hair sample method proves accurate enough,
they may switch to the hair samples completely. Vetgen itself ( http://www.vetgen.com/oborder.html
) charges a variable amount depending on the number of horses, ranging
from $140 for a single test down to $99 for 16 or more tests. Below are
sites with more information on SCID itself.
http://www.morab.com/teller/tellermedical.html#SCID
http://66.216.19.63/scids/scidsinfo.html