What’s the Scoop?
Blood type and Horses
I have always been vaguely interested in equine genetics of
all different sorts. I have a more than
basic understanding of equine color genetics and am always fascinated about the
newest testing coming out for various inherited equine genetic disorders. From this general line of thought, I started
looking into equine blood types. I
understand human blood typing as I have worked as a blood banker, but horses
are an entirely different situation!
I decided to do a friendly little post with some of the basic overviews in case
anyone else out there enjoys a good read!
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From my general research there are seven accepted red blood
cell systems A, C, D, K, P, Q, and U.
It
also appears that there may be an 8
th system that is not universally
accepted yet.
Within each system, are multiple antigenic sites known as factors.
Think of the A, C, D, K, P, Q, and U as
houses and the factors are different rooms within the house.
The factors are listed in parentheses after
the systems so it ends up looking like this: A (a,b,c), Ca, Ka, P (a,b), Q
(a,b,c), and Ua.
The most common blood type for a horse is Aa Ca+.
Here is a fun chart taken from UC Davis with
the breakdown between breeds and blood type.
So it looks like the breeds most commonly being AaCa+ include Thoroughbreds and
Arabians.
How fun!
Humans naturally form antibodies to other blood types so a blood type and
antibody screen is imperative before attempting a transfusion.
There is of course, the universal donor type
(O negative), which is compatible as it has a lack of antigens more than
anything else.
However, horses
apparently don’t naturally develop antibodies to other blood types, so usually
the first blood transfusion, even if with a different blood type isn’t of
consequence.
The exception of this are
broodmares that may have been sensitized from previous pregnancies.
Some people may have heard of women having issues with their
pregnancy from different blood types.
Rhogam is a product commonly issued to RH negative women who have RH
positive babies. Humans are a little bit
different than horses in that RH antibodies (as well as others!) generated by
the mother against her child can cross the placental barrier and can cause
Hemolytic Disease of the Newborn.
In horses, this is a little bit different in the fact that while a mare may in
fact have antibodies against her foal’s red blood cells, until that foal
actually ingests colostrum containing these antibodies, they are generally
healthy and safe. Neonatal
isoerythrolysis is what develops if this foal would consume colostrum
containing these antibodies. This
results in anemia, jaundice, destruction of red cells, increased heart rate and
all around bad things. This is somewhat
more common in certain breeds, including Friesians. It is also common in mare to donkey
breedings.
The likelihood of this disease can be screened for by taking blood samples from
both the sire and dam. If likely, the
foal should be muzzled after birth.
So if anyone else is a happy nerd, hope you enjoyed this scoop and just look at
your horse and marvel at how many potential blood types they have!