Cats have the following blood types, which vary between countries:
- A (40-90%)
- B (10-30%)
- AB (9%)
- Mik antigen (<1%)
See also: Breed blood type frequencies
- British, Turkish van and Turkish angora have a higher prevalence of type B
- Siamese, Tonkinese and Bengal are only of type A
Only one major blood group system has been identified for the domestic cat, whereas a plethora of systems are recognized in dogs, humans, horses and other species. Except in primates, no gene mutations have been identified that cause the many animal blood groups. The major blood group system of the domestic cat was identified in the early 1900's and was later found to contain two types as determined by agglutination by naturally occurring alloantibodies. The two major blood types are called type A and type B. The common types are allelic, with type A dominant to type B. A rare type AB, which shows agglutination with both anti-A and anti-B, has not been as clearly defined, but is suspected to be allelic to types A and B . Several studies have shown familial segregation for cat blood types A and B. However, families segregating for type AB are limited and the parentage of the matings was not confirmed. Therefore, the inheritance of the third type AB allele was not clearly resolved, although it appears to be recessive to type A and dominant to type B.
The ability to determine feline blood types is especially important because of the phenomena of neonatal isoerythrolysis, DIC and transfusion reactions between previously non-sensitized donors. Similar to the unrelated ABO system of humans, cats often possess alloantibodies against their opposite blood type. Blood type B cats possess strong agglutinins and hemolysins to type A red cells. Type A cats possess alloantibodies that are less strongly reactive for type B red cells. Thus, a blood transfusion of a type B cat with type A blood can cause a severe reaction. Milder reactions occur if type B blood is transfused into a type A cat. Interestingly, blood type AB cats are universal recipients since they lack alloantibodies against either blood type. The presence of strong, naturally occurring alloantibodies in the type B cat against the A antigens also leads to neonatal isoerythrolysis for type A kittens born from a type B queen. The prevention of transfusion reactions and neonatal isoerythrolysis requires close monitoring of blood types of donor and recipient, and toms and queens.
There is no "universal donor" blood type in cats - a very small amount of the wrong blood type can kill a cat if is is sensitized to the blood. This can be an issue in some cat breeds. In particular, British, Cornish rex and Devon rex cats, where the percentage of Type B cats is much higher, perhaps as high as 50%. Other breeds with significant percentages of Type B blood include the Abyssinian, Himalayan, Japanese bobtail, Persian, Somali and Sphinx breeds.
Typing the queen and tom before mating
Prevention involves blood typing the queen and any prospective tom that she may be mated with. Cats get one gene for blood type from their mother (in the egg) and one from their father (in the sperm). The genes for blood type A are dominant to the genes for blood type B, which means that a cat with a mixture of genes – Ab (note that this is different from the third, rare, blood group AB) – will have blood type A A blood group B queen can give birth to a blood type A kitten if mated to a blood type A tom carrying the genes for blood type B, (as in figure below). This is the situation in which neonatal isoerythrolysis is most likely to occur.
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