Blood Typing and Donation
"I want this patient typed and cross-matched. Stat!" Those are familiar lines, to be sure, of any fan of the real or fictional medical dramas on TV today. But did you know that this is just as important a procedure for cats as it is for humans? This page is designed to teach you about blood types, what is special about them in cats, and what dangers they may pose to your cat (either through transfusion or breeding). Also, if you have your cat typed and he or she is a type B, we would like to ask you to consider pledging your cat to be a donor on our "B Team."
The Basis of Blood Types
As in humans, cats have a system of blood types. The feline AB blood group system consists of three different blood types: type A, type B, and type AB. (They are unrelated to the human ABO group, however.) The different blood types are caused by A and/or B antigens (a specific protein) that resides on the surface membrane of the cat’s red blood cells.
About one third of type A cats possess an anti-B antibody (a protein that identifies a particular antigen as something foreign and in need of destroying) in low concentrations in their blood plasma. All type B cat possess an anti-A antibody in high concentrations in their blood plasma. Since type AB cats have both A and B antigens on their red blood cells, they do not have anti-A or anti-B antibodies.
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Variation of Types among Breeds
Although type A is the most common blood type, the frequency of type A and B in domestic shorthair cats varies worldwide and markedly among breeds. Type AB occurs extremely rarely and so is not included in the following table of blood type frequency in American cats.
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| Breed | Type A | Type B | Breed | Type A | Type B |
| Abyssinian | 86 | 14 | Himalayan | 93 | 7 |
| Birman | 84 | 16 | Japanese Bobtail | 84 | 16 |
| British Shorthair | 60 | 40 | Maine Coon | 98 | 2 |
| Burmese | 100 | 0 | Norwegian Forest | 93 | 7 |
| Cornish Rex | 66 | 34 | Persian | 84 | 14 |
| Domestic Shorthair | Scottish Fold | 82 | 18 | ||
| Northeast | 99.7 | 0.3 | Siamese | 100 | 0 |
| Northcentral | 99.6 | 0.4 | Sphinx | 81 | 19 |
| Southeast | 98.5 | 1.5 | Somali | 83 | 17 |
| Southwest | 97.5 | 2.5 | Tonkinese | 100 | 0 |
| West Coast | 95.3 | 4.7 | |||
Transfusion Dangers
Transfusion therapy has become an integral part of the supportive management of critically ill and anemic cats. Anemia is by far the most common reason for transfusion and may be caused by 1) blood loss due to fleas, surgery or trauma; 2) destruction of red blood cells induced by toxins, hemobartonellosis, or FeLV infection; and 3) reduced red blood cell production associated with FeLV infection or chronic renal failure. A quarter of all transfusions are given to non-anemic cats for various reasons.
Blood typing your cat is important to prevent hemolytic transfusion reactions. These reactions occur when a cat is transfused with an incompatible blood type. Type B cats exhibit an immediate and catastrophic anaphylatic reaction (drop in blood pressure, slowed heart rate, cessation of breathing, urination, defecation, vomiting, and neurological depression) and hemolytic signs (drop in red blood cell numbers and bloody urine) when transfused with type A blood because of their anti-A antibody. The transfused blood may survive just minutes, and only 1 mL may result in a fatal reaction. Type A cats may exhibit only a mild reaction when transfused with type B blood, but even this can make a difference in the cat’s recovery rate. Also, the transfused red blood cells have a shortened life span. Some type A cats will not exhibit a reaction on the first transfusion of type B blood, but will, as a result, develop moderate concentrations of anti-B antibodies. Upon a subsequent incompatible transfusion, a serious reaction will occur.
Breeding Risks
Blood typing your cat is also important in making breeding decisions. Neonatal isoerythrolysis (fading kitten syndrome) can occur when the maternal and fetal blood types are incompatible. This happens when a type A tom is bred to a type B queen. Most of the kittens will be type A. The red blood cells of the type A kittens will be destroyed when they nurse on the mother’s first milk, the colostrum. This special milk contains maternal antibodies necessary for building up the kittens’ immune systems; this includes the anti-A antibody. The kittens can seem normal at birth, but develop signs after nursing, fade, and die within the first days of life.
Typing
There is a simple and fast in-office test for determining your cat’s blood type; please ask the doctor for more information.
Become a Member of the “B Team”
Because of the relative rarity of type B blood, it is important to have donor cats identified before a need arises. The ideal feline blood donor is a shorthaired, large but lean, healthy, young cat. Donors should also be strictly indoor cats and preferably single pets. All standard vaccinations must be current, and the cat should not be on any medications. Complications from blood donation are few, and cats are closely monitored throughout the donation process. If you are interested in your cat becoming a member of our “B Team,” please let the doctor know so she can discuss the program with you.
