The AB system is the major blood group system in domestic cats. The common blood types are A and B. Cats with blood type A have naturally occurring anti-B antibodies at a low titer and cats with blood type B have naturally occurring anti-A antibodies at a high titer. A third rare type "AB" is also known. Cats with the rare "AB" type do not have anti-A or anti-B antibodies and are thus universal recipients for blood transfusion. It should be noted that the nomenclature of cat blood groups is confusing; the "AB" type is not the result of presence of the A and B blood groups. There is no null phenotype.
Detailed AB Blood Group Information
The presence of naturally occurring antibodies makes it necessary to cross-match blood for transfusion purposes. In cats, these natural antibodies can cause neonatal isoerythrolysis (NI). NI occurs when a B-type queen is bred to an A-type tom and the A-type kittens absorb the anti-A antibodies from the colostrum when they nurse. The hemolytic disease that ensues can be lethal.
The A and B blood groups are genetically determined. The following nomenclature has been proposed for the blood group alleles: A for A, a for AB and b for B. Blood type A is dominant to B. Genetically, cats with type A can be A/A, A/a or A/b and cats with type B are always b/b. Blood type A is the most common among cats but the frequency varies significantly by breed and geographic location. Breeds that do not have the B type are Siamese, Burmese, Russian Blue, Ocicat and Oriental Shorthair. Breeds with high incidence (up to 60%) of the B blood type are Exotics, British Shorthair, Cornish Rex and Devon Rex. The inheritance of the rare "AB" group is not well understood. The incidence of the "AB" type is reported to be less than 1%.
A genetic mutation associated with the B blood group in most cats has been identified and a DNA test has been developed. Animals can be tested at an early age from a buccal swab. Cat breeders can benefit from this test for mate selection to avoid production of NI kittens.
The DNA blood group test identifies cats that have the B serotype (two copies of b allele) and also that are B carriers (one copy of the b allele, A or AB serotypes). Because the DNA test cannot distinguish between a Type A versus a Type "AB" cat, the non-b allele is reported as "N". The cat could have a Type A or Type AB serotype.
The cat blood group DNA test is available to all breeds. In about 2% of the cases, results are inconclusive and status of the B blood group cannot be determined in some cats. This indicates that there are additional mutations yet to be identified. Blood group tests that are inconclusive will be refunded.
Results reported as:
|Test Result||Blood group status|
|N/N||Cat is Type A or Type "AB"|
|N/b||Cat is a carrier of B factor; serotype could be Type A or Type "AB"|
|b/b||Cat is Type B|
The blood group test has been validated for domestic cat breeds only. The accuracy of results for wildcats and hybrids (Servals, Bengals, Chaussies) has not been determined. Because of the lack of sufficient samples from wildcats and F1 hybrids, the genetics of wildcat AB blood group is not well understood.
Bighignoli B, T Niini, R Grahn at al. Cytidine monophospho-N-acetylneuraminic acid hydroxylase (CMAH) mutations associated with the domestic cat AB blood group. BMC Genetics 2007; 8:27 doi:10.1186/1471-2156-8-27