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Blood types



  • In cats there is a well-established A-B blood group system based on naturally occurring alloantibodies, which has important clinical implications.
  • A-B blood group system is inherited via two alleles at the same gene locus in a simple dominant form, the allele for group A being dominant over that for group B.
  • A very small proportion of cats (<6%, in most countries <1%) have a third blood type (Type AB) These cats have both A and B antigens, but no pre-existing anti-A or anti-B antibodies. Blood type AB is inherited separately as a third allele that is recessive to the A allele and dominant to the B allele. Because the nomenclature is confusing, this serotype is sometimes referred to as Type C.
  • Type AB cats are only found in breeds that also show the Type B phenotype.
  • Cats expressing the group A phenotype (Type A cats) are either a homozygous (A/A) or heterozygous (A/B or A/C) genotype.
  • Cats expressing the group B phenotype (Type B cats) are invariably homozygous for the B allele (B/B).
  • Blood Type AB cats may have the genotype C/C or C/B.
  • Recently a group in the USA reported a non-A-B blood group system, based on a novel feline erythrocyte antigen named Mik.
  • A feline patient's blood type (serotype A, B, or AB) can be demonstrated using a patient-side kit.
  • If required (eg prior to mating), genotype can be determined with a genetic test (blood test or cheek swab). This test does not differentiate between Type A and Type AB serotype however.
  • Neither method can detect the Mik antigen; suspicion for the presence of this could be gained via an incompatible cross match.
  • Genetic testing has also revealed the presence of more than one mutation that may be associated with the Type B phenotype. In about 3% of cats, the genotype cannot be determined with the current genetic methods, likely indicating that there are other mutations that have not yet been determined. This may account for incompatibilites of cross match between cats of the same blood type.
Print off the Feline blood groups and incompatibilities Owner Factsheet to give to your client.

Clinical significance of feline blood groups

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Prevalence of feline blood types

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kehl A, Mueller E, Giger U (2019) CMAH genotyping survey for blood types A, B and C (AB) in purpose-bred cats. Anim Genet 50 (3), 303-306 PubMed.
  • Forcada Y, Guitian J & Gibson G (2007) Frequencies of feline blood types at a referral hospital in the south east of England. JSAP 48 (10), 570-573 PubMed.
  • Weinstein N M, Blais M C, Harris K et al (2007) A newly recognized blood group in domestic shorthair cats: the Mik red cell antigen. JVIM 21 (2), 287-292 PubMed.
  • Knottenbelt C M (2002) The feline AB blood group system and its importance in transfusion medicine. J Feline Med Surg (2), 69-76 PubMed.
  • Knottenbelt C M, Day M J, Cripps P J et al (1999) Measurement of titers of naturally occurring alloantibodies against feline blood group antigens in the UK. JSAP 40 (8), 365-370 VetMedResource.
  • Knottenbelt C M, Addie D D, Day M J et al (1999) Determination of the prevalence of feline blood types in the UK. JSAP 40 (3), 115-118 PubMed.
  • Lubas G & Continanza R (1995) Recent advances in our understanding of the immunohaematological characteristics of cats and their clinical application. EJCAP (1), 47-54 VetMedResource.
  • Giger U, Bucheler J & Patterson D F (1991) Frequency and inheritance of A and B blood types in feline breeds of the United States. Journal of Heredity 82 (1), 15-20 PubMed.
  • Giger U, Griot-Wenk M, Bucheler J et al (1991) Geographical variation of the feline blood type frequencies in the United States. Feline Practice 19 (6), 21-27 VetMedResource.

Other sources of information

  • Bighignoli B, Owens S D, Froenicke L, Lyons L A (2010) Blood types of the domestic cat. In: Consultations in Feline Internal Medicine 4. August J R (ed), pp 628-638.
  • Giger U (1992) The feline AB blood group-system and incompatibility reactions. In: Current Veterinary Therapy XI. Kirk R W & Bonagura J D (eds). Philadelphia: W B Saunders, pp 470-474.

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