Van der Merwe L.L. BVSc Hons MMed(Vet) Small Animal Medicine

Department of Companion Animal Clinical Studies (Outpatients), Faculty of Veterinary Science, Private Bag X04, Onderstepoort 0110.



Feline Blood Groups

Feline blood groups have been characterized as Type A, Type B and Type AB, with Type A being most prevalent. The frequency of the blood types differs markedly between different breeds of cats and also between different geographical areas ( table 1).



Breeds Country Type B frequency
Siamese, Burmese, Tonkinese and Russian blue


USA      0%


UK      17%
Maine Coone, Norwegian Forest


USA      1 – 10%
Abyssinian, Birman, Persian, Somali, Sphinx, Scottish fold


USA      11 – 20%


UK      24%
Cornish Rex, Devon Rex


USA      20 – 45%
Devon Rex


SA      50%
Exotic and British short hair


UK and USA      53 – 58%
Domestic shorthair


UK, USA,      < 3%
Domestic shorthair


Australia      26%




The feline blood group antigens are inherited as a simple autosomal mendelian trait with A being dominant over B. Unlike dogs, cats possess naturally occurring antibodies (allo-antibodies) against other blood groups which may result in life threatening haemolytic transfusion reactions if incompatible blood is transfused.


Alloantibodies can be transferred via colostrum for up to 16 hrs after birth. All type B kittens, and to a lesser extent, type A kittens develop allo-antibodies between 6 – 10 weeks of age in an immune response believed to be triggered by common food and bacterial antigens.


Type B cats have high titres (1:64 – 1: 2064) of anti-A antibodies. These antibodies are mainly of the IgM class and are strong haemolysins and haemagglutinins. Type A cats develop only low titres (1:2 – 1:32) of mild anti-B antibodies that consist of both IgG and IgM which accelerate the destruction of incompatible transfused red cells. Type AB cats contain no allo-antobodies thus are universal recipients.


Feline blood typing

Simple typing cards are available for feline blood typing and require only a drop of EDTA blood. Blood typing will detect an incompatibility with the blood type antigens only, whereas crossmatching detects any incompatibility in the serum of the recipient or donor.


Blood typing provides an answer to the phenotypic characteristics of the cats’ blood group. A cat designated as type A phenotypically may be genotypically type AB. Thus blood typing without progeny testing does not allow identification of a cats’ genotype.


Phenotype A    – Genotype A A

– Genotype A b

Phenotype B    – Genotype b b


Neonatal Isoerythrolysis




There is minimal if any transfer of maternal immunoglobulins across the feline placenta which is endotheliochorial, colostrum is thus a vital source of immunoglobulins for the neonatal kitten. Gastrointestinal absorption of large proteins occurs only up to 16 hours post partum.


NI is a risk in all type B queens bred to Type A males. As all type A cats have high levels of anti-A antibodies any blood type A progeny which ingest colostrums from the queen will develop a degree of NI as these anti-A antibodies will cross into neonatal circulation and target blood cells. This can happen even in primiparous females as the antibodies are alloantibodies.


Clinical Signs:


Clinical signs vary depending of the amount of anti-A antibodies in the queens’ plasma as well as the amount ingested by the kitten. The characteristic sign is severe pigmenturia due to haemoglobinuria. Other signs include sudden death, fading kitten syndrome, icterus and tail tip necrosis. Removal from the queen after signs have developed will be of no benefit and the mortality rates are high.




Proper selection of breeding pairs:

Neonatal isoerythrolysis will only occur with a type B female        therefore a type B female should not be bred with a type A male.


The progeny of such a mating are shown in the tables below. Remember that each individual kitten has an equal chance of any of the possible genotypes, so it is impossible to predict the genotype or phenotype of the kittens by the parents’ phenotype.


Table 2: Diagrammatic representation of inheritance mode


AA bb Ab bb
Progeny: Ab Ab Ab bb

In a mating with a homozygous type A male ALL the progeny will be phenotype A and be at risk for NI


In a mating with a heterozygous type A male there is a 50% chance of a kitten being type A thus theoretically 50% will be at risk for NI



  1. b) Breeders , however are often selecting for physical characteristics such as coat colour and conformation and want to breed with an incompatible pair regardless. In this situation nursing from the queen is not allowed in the first 24 hours. This obstacle can be overcome if another cat of blood group A is in lactation at the time of partus. The new born kittens can be placed with a foster mother for the first 24 hours of life to allow intake of antibody rich milk and thus receive IgG and transfer of passive immunity. Once the capacity for the GIT to absorb large molecules has waned (16 hrs) the kittens can be returned to their mother.


Colostrum is generally thought to have higher concentrations of antibodies than milk, but in felines the levels of antibodies in milk is almost as high as that of colostrums or serum.


The half-life of maternal IgG is 4.4 ± 3.6 days. Thus IgG titres in neonates peak in the fist day and steadily decline whereas IgM titres steadily increase from the first week of life.


  1. In the absence of another queen to allow them to suckle the kittens can be fed milk replacer and transfer of immunity can be accomplished by the parenteral supplemental of adult cat serum.


Serum donors should be blood typed to prevent inadvertent administration of type B serum to type A kittens.


A study was conducted to establish the viability of transfer of passive immunity by the injection of adult feline serum; 5ml at birth and 12 and 24 hours after birth. The injections were given sub-cutaneously or intra-peritonealy. The result of this study showed that 150 ml/kg (15 ml / 100g) will successfully correct IgG deficiency of colostrums deprived kittens producing serum concentrations comparable to those in kittens which nursed from birth to 6 weeks of age.

Peak serum IgG levels in nursing kittens ranged between 1080 – 2400 mg/dl and from 910 – 2400 mg/dl in kittens receiving serum. Serum IgG concentrations gradually declined to a nadir between 3-5 weeks and did not differ between colostrums fed and serum treated kittens. The minimum serum IgG needed to confer protection in kittens is unknown but current recommendations in large animals suggest a value of 400 – 800 mg/dl.


If the breeder has stores of serum it is feasible to give some serum per os, but the volume required in the first 16 hours (10 -15 ml) exceed the stomach capacity of a neonatal kitten.


Feline Blood typing – Practicalities




  1. Büchler J 1999 Fading Kitten syndrome and neonatal isoerythrolysis. Veterinary Clinics of North America: Small Animal Practice Vol 29 (4) pg 853 – 870
  2. Griot-Wenk ME, Giger U. 1995. Feline Transfusion Medicine: blood types and their clinical importance. Veterinary Clinics of North America: Small Animal Practice Vol 25 (6) pg1305 – 1322
  3. Giger U, Casal ML .1997 Feline Colostrum-friend or foe:maternal antibodies in queens and kittens. Journal of Reproduction and Fertility Vol 51 pg 313 – 316
  4. Levy JK, Cawford CP, Collante WR, Papich MG. 2001 Use of adult cat serum to correct failure of passive transfer in kittens. Journal of the American Veterinary Medical Association. Vol 219 (10) pg 1401 – 1405




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