Q I just purchased a lovely Persian kitten, and the breeder told me to make sure my veterinarian tests to see what my kitten's blood type is. I've had cats all my life, and I never knew they had different blood types. Is this something new?

A No, it's not really new; the feline AB blood group system was first described back in the early 1960s. There are three blood types in cats: type A, type B, and the rare type AB. Almost all non-purebred cats from the United States have type A blood. Non-purebred cats with type B blood are much more common in other parts of the world. For example, over one fourth of Australian domestic shorthaired and longhair cats have type B blood.

Among pedigreed (aka "purebred") cats, the proportion with type A blood is mostly dependent on the breed. For example, 100 percent of Siamese cats have type A blood, but the percentage falls to about 40 percent in British Shorthaired; the remainder is either type B or AB. The other breeds tend to fall somewhere between these extremes. Your Persian kitten has about a 25 percent chance of having type B blood.

When a blood transfusion is needed
It's safest to give type A blood to a type A cat, and type B blood to a type B cat. But what if the donor's blood type doesn't match that of the recipient? Well, it depends. If type B blood were given to a type A cat (that had never received type B blood in the past), usually only a mild transfusion reaction would ensue - so mild that it may not even be noticeable over the short term. But if a type B cat were to receive type A blood, an extremely rapid, severe, and potentially fatal reaction would occur, even if just a few milliliters of blood were to be given.

Veterinarians don't usually emphasize blood typing non-pedigreed cats - they're almost all type A. Most donor cats aren't pedigreed either, so it would be highly likely for both donor and recipient to have the same type A blood. But many pedigreed cats have type B blood, so it is extremely important that people caring for these lovely creature know the blood type before a transfusion. Determining your cat's type is a simple procedure requiring only a few drops of blood in most cases-and it could be a real lifesaver should your cat ever need "the gift of life."