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Background

The presence of naturally occurring (i.e. without the need for a previous blood transfusion), high titre antibodies to type A blood in type B cats can cause neonatal isoerythrolysis (NI), a bursting of the red blood cells.


This can occur when a type B queen is bred to a type A tom. Any type A kittens produced from the mating will absorb the anti-type A antibodies in their mother’s colostrum during the first day of life, and these antibodies can mediate haemolysis (bursting) of the kitten’s type A red blood cells, which can be lethal. It is therefore important for breeders to test the blood type of breeding queens, allowing them to identify the risk of NI. Additionally, the genetic test can identify cats that carry one b allele whereas serological blood typing cannot identify carriers of b.

Cats have one common blood group with three blood types: type A, type B and the rarer type AB. The following nomenclature is used to define blood type alleles/variants:

  • A for blood type A
  • a or sometimes c for blood type AB
  • b for blood type B

Please note: the rare AB blood type is not the result of one copy of the A allele and one copy of the b allele; it is a separate blood type reported to be present in less than 1% of cats. The genetics of blood type AB are not well understood.

About our tests

Blood type (All breeds) - previously this test was called Feline Blood type

Our genetic test for Blood Type (All breeds) identifies two recessive b alleles that are associated with type B blood in all breeds* of cat. Professor Leslie Lyons’ research team discovered the original mutation in the cytidine monophospho-N-acetylneuraminic acid hydroxylase
(CMAH) gene associated with B blood type (termed b1).


Later, our research identified a further mutation, termed b2 (previously reported as ‘unusual genotype’), that also appears to be linked to blood type B in cats. The b2 mutation is rare but has been observed in cats from the UK, Mainland Europe and the USA in several breeds including
Bengal, BSH, Devon Rex, Egyptian Mau, Ragdoll, Siberian and Turkish Van.


By including these two mutations together in our Blood type (All breeds) test the accuracy is ~97% at predicting b blood type in pure breed cats. In about 3% of cats the genetic results from this test do not match the conventional blood typing results, indicating that there are additional
mutations yet to be identified.


*Some breeds do not have the b allele (Siamese, Burmese, and Oriental Shorthair).

Blood type b3 (Ragdoll and related breeds)

Recently, we have added this new test to identify a newly discovered third recessive type b allele, associated with B blood type in Ragdolls and related breeds plus Scottish Folds.**


Please note: it is recommended that breeders of Ragdoll, Ragamuffin and Scottish Fold cats test for both the Blood type (All breeds) and the Blood type b3 (Ragdoll and related breeds) tests in order to get a complete blood type result. This combined result is reported as ‘Feline Blood
Group’. Any submissions from these breeds for just Blood type (All breeds) will be contacted and encouraged to add the Blood type b3 test.


If only the Blood type (All breeds) test is run on these breeds then the accuracy of the blood type results reported is significantly reduced and should not be used for breeding compatibility decisions.


** This is a newly discovered mutation, as more data is gathered about this mutation it may be found in breeds other than those listed. We will update our testing advice accordingly.

What are the genetics of cat blood types?

During red blood cell development, the ‘B’ form of neuraminic acid is converted to the ‘A’ form by the enzyme cytidine monophospho-N-acetylneuraminic acid hydroxylase (CMAH).


Mutations in the CMAH gene disrupt this enzyme activity and result in the presence of different neuraminic acid residues on the surface of red blood cells. Type A cats have the ‘A’ form of neuraminic acid, type B cats have the ‘B’ form of neuraminic acid and type AB cats have both forms.


Blood type A is dominant to blood type B, meaning that two mutated copies of the b allele (whether the same or different eg b1/b1 or b1/b3) are required for a cat to be type B; i.e. one allele from the tom and one from the queen. Cats with only one copy of any b allele can be blood type A or type AB. Our genetic tests cannot distinguish between blood type A and type AB.


The mutations causing blood type AB in most cats are unknown, although they are thought to be recessive to type A and dominant to type B.


The naming system of the blood types can be confusing as the rare AB blood type is not genetically equivalent to having one copy of the type A gene and one of the type B gene, it is a separate blood type (sometimes called Type C) reported to be present in less than 1% of cats, but more common in Ragdolls (18%).

Why is blood type important?

Cat breeders want to avoid a condition called Neonatal Isoerythrolysis (NI) or ‘fading kitten syndrome’. NI typically happens when blood type A or AB kittens are born to a blood type B queen.


Blood type A cats usually have naturally occurring, low titre antibodies to type B blood.


Blood type B cats usually have naturally occurring, high titre antibodies to type A blood.


The presence of these naturally occurring (i.e. without the need for a previous blood transfusion), high titre antibodies to type A blood in type B cats can cause neonatal isoerythrolysis (NI).


As type B queens usually have high levels of anti-A antibodies in their blood, which are secreted into their colostrum (the first bit of milk produced by the female when the kittens are first born, which is rich in antibodies) all their kittens get a high dose of anti-A antibodies when they suckle. These antibodies will bind to the type A or AB red blood cells of any kitten that is not blood type B, causing the cells to burst creating severe anaemia which can be fatal.


The reverse scenario of a type A or AB queen giving birth to type B kittens rarely results in NI because type A queens usually have low levels of anti-B antibodies in their blood, and these antibodies rarely cause anaemia in the type B kittens.


The number of kittens affected will depend on the genotype of the tom.

  • If a blood type A or AB (does not carry b) tom, is mated to a blood type B queen, then all of the kittens will be blood type A or AB (carrier of b) and therefore all at risk of NI.
  • If a blood type B queen is mated to a blood type A or AB (carrier of b) tom then each kitten will have a 50% chance of being blood type B and a 50% chance of being A or AB (carrier of b). Any A or AB (carrier of b) kittens born will be at risk of NI.


Severity of disease with NI will depend on the amount and nature of the antibodies produced by the queen and absorbed by the kitten; large amounts of highly agglutinating antibodies will cause the most severe disease. Unfortunately, we are not able to determine the amount and nature of the antibodies produced by a type B queen.

Interpretation of results

Cats with two copies of any b allele, whether the same or different, have type B blood. Cats with only one copy of any b allele (carrier of b) can be blood type A or type AB.


Please Note: Our genetic blood type tests cannot distinguish between blood type A and type AB. The AB blood type is rare in most breeds of cat but has been reported to be more common in Ragdolls (~18% prevalence).

Blood Type (All Breeds) - tests for the presence of b1 and b2

Genetic Result

Interpretation

Blood type A or AB (does not carry b) 

Cat has blood type A or AB

Blood type A or AB (carrier of b1)
Blood type A or AB (carrier of b2)

Cat has blood type A or AB
The cat is a carrier of b1 or b2 (previously named ‘unusual genotype’)

Blood type B (b1/b1)
Blood type B (b1/b2)
Blood type B (b2/b2)

Cat has blood type B
The cat has two copies of any b allele

Feline Blood Group - combined result of Blood Type (All Breeds) and Blood Type b3 (Ragdoll and related breeds). Tests for the presence of b1, b2 and b3

Genetic Result

Interpretation

Blood type A or AB (Does not carry b)

Cat has blood type A or AB

Blood type A or AB (Carrier of b1)

Blood type A or AB (Carrier of b2)

Blood type A or AB (Carrier of b3)

Cat has blood type A or AB
The cat is a carrier of b1,b2 or b3

Blood type B (b1/b1)

Blood type B (b1/b2)

Blood type B (b1/b3)

Blood type B (b2/b2)

Blood type B (b2/b3)

Blood type B (b3/b3)

Cat has blood type B
The cat has two copies of any b allele

How do I select a safe blood type pairing for breeding?

Blood type A or AB Males

Can be mated to Females that are:

- Blood type A or AB (does not carry b)
- Blood type A or AB (carrier of b)


We do NOT recommend breeding to a Female that is Blood type B, as this can cause neonatal isoerythrolysis.

Blood type B Males

Can be mated to Females that are:

- Blood type A or AB (does not carry b)
- Blood type A or AB (carrier of b)
- Blood type B

Blood type A or AB Females

Can be mated to Males that are:

- Blood type A or AB (does not carry b)
- Blood type A or AB (carrier of b)
- Blood type B

Blood type B Females

Can be mated to Males that are:

- Blood type B

 

We do NOT recommend breeding to Males that are:

- Blood type A or AB (does not carry b)
- Blood type A or AB (carrier of b)

This can cause neonatal isoerythrolysis.

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