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AB Blood Group in Felines

Introduction

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.

Procedure for collecting a feline DNA sample

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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 also cause neonatal isoerythrolysis (NI). NI occurs when a B type queen is bred to an A or AB type tom and the A and AB type kittens absorb antibodies from the colostrum when they nurse. The hemolytic disease that ensues can be lethal.

The A, B and AB blood groups are genetically determined. To avoid confusion, the following nomenclature has been proposed for the blood group alleles (variants): A represents serotype A, b represents serotype B and “c” represents serotype AB. This nomenclature avoids confusion in DNA reports between type A carrying the b allele (A/b) and the rarer blood group AB. The order of dominance is A>c>b. Genetically, cats with type A can be A/A, A/c or A/b, cats with type AB can be c/c or c/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 incidence of the AB type is reported to be less than 6% depending on country and breed.

A genetic mutation associated with the B blood group in most cats has been identified and a DNA test has been developed. More recently, the causative mutation for serotype AB specific to Ragdolls and some random bred cats has been identified in Dr. Leslie Lyons’ laboratory at the University of Missouri. Animals can be tested for these alleles at an early age from a buccal swab and breeders can use this test for mate selection to avoid production of NI kittens.

The DNA blood group test identifies cats that are either serotype B (b/b) or that are B carriers (one copy of b). It also identifies some Ragdolls and random bred cats that are serotype AB (c/c and c/b) or AB carriers (N/c).  Cats that are not genetically c/c, c/b or b/b could be serotype A or another serotype AB (yet to be identified), thus the ambiguous allele is reported as N (not b or c variants).

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 for these 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
N/c Cat is a carrier of AB factor; serotype could be type A or type AB
c/c Cat is type AB
c/b Cat is type AB; Carrier of B factor
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.

Reference:

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

 
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