Feline AB Blood Types

In cats only the AB blood group system has been recognized. There are three blood types:Type A, Type B, and Type AB. Type A is most common, and is dominant to type B. The rare type AB being inherited separately. While type A has the highest frequency in all breeds, the frequency of type B may vary from none, as in the Siamese and related breeds, to around 40% as in the British and Exotic Shorthair and Devon and Cornish Rex breeds.

Because cats have naturally occurring alloantibodies, serious transfusion reactions may occur when a patient receives just a small amount of unmatched blood for the first time. In particular, type B cats have very strong antibodies against type A cells. Type A cats generally have weak antibodies against type B cells and type AB cats have no alloantibodies. Thus, only blood type matched transfusions can be administered safely. Transfusion reactions can be avoided by typing all donors and recipients

Type B queens have strong anti-A antibodies in colostrum that may be absorbed by kittens during the first day of life. Type A or AB kittens nursing from a type B queen are at a great risk to develop neonatal isoerythrolysis, characterized by dark urine, jaundice and death during the first week of life, unless the kittens are removed from the type B queen and foster nursed for the first 24 hours. Breeding cats need to be typed and type B queens should not be bred to type A toms. Neonatal isoerythrolysis can be prevented by typing all breeding cats and avoiding matings between type B queens and type A toms.