Do Cats Have Blood Types?

In domestic felines, we can find three main blood types. These are grouped according to the antigens they present on the membrane of their erythrocytes (red blood cells). They are from a combination of AB types: A, B and AB. Since blood type is determined by genetics, the breed of cat will have a bearing on what blood group they belong to.

Blood group A cat breeds

Group A is the most common of the three main feline blood types. These include the European Shorthair, a pedigree breed closely associated with mixed-breed cats. The following breeds are most commonly

• European cat
• American shorthair
• Maine coon
• Manx
• Norwegian Forest

Due to their genetic lineage, some cat breeds will only have one type. These include the Siamese, Oriental and Tonkinese cats, all of which are types of Asian cat breeds.

Blood group B cat breeds

The cat breeds in which group B predominates include:

• British Shorthair
• Devon Rex
• Cornish Rex
• Ragdoll
• Exotic

Cat breeds of group AB

The AB group is very rare to find, but can be found in:

• Turkish Angora
• Turkish Van

The blood group that a cat has depends on their parents, since it is inherited through genetics. Each cat has one allele from the father and one from the mother, this combination determining their blood group. Allele A is dominant over B and it is even considered dominant with AB. This is why a cat requires both B alleles to be blood type B. The combinations of different cat blood types are:

• A cat with A blood type would present one of the following combinations: A / A, A / B, A / AB.
• A cat with B blood type is always B / B because it is never dominant.
• A cat with AB blood type will be AB / AB or AB / B.

Rare Mik- feline blood type

While the vast majority of cats will be from the AB antigen blood groups, there has been another group only identified in 2007^[2]. This is known as the Mik- blood group. Its gene sequence has not been properly mapped, making it the rarest blood type in cats. However, it is important we know whether a cat has the Mik- blood type, otherwise it can be fatal if they are given the wrong blood transfusion.

There are several tests which determine the specific antigens of the red blood cell membrane. In determining these antigens, we can find out the blood type of a cat. An ethylenediamine tetraacetic acid (EDTA) blood test is carried out, something which is used for testing cats for various diseases. It can also be used to determine the blood group, in part determined by whether or not the blood agglutinates (clumps together).

The blood is placed on cards to test for the blood type, so it is an easy process. However, when a veterinary clinic does not have the cards, they will need to send a blood sample to a laboratory for further testing.

In an emergency, it is essential a blood compatibility test is carried out. Cats have natural antibodies against the membrane antigens of other blood groups, meaning the cat's body will reject the blood after a transfusion.

Transfusions will react in different ways. For example, all cats with group B blood have strong anti-group A antibodies. If a cat with blood type A has a transfusion of type B blood, the reaction can be extreme and will likely result in the death of the cat. Blood type A has antibodies against type B blood, but they are weaker than vice versa. Cats with AB blood do not have antibodies against A or B blood types. This means AB blood type cats can have transfusions of both A and B blood.

In some cases of anemia in cats, the feline will need a blood transfusion. This is because cats with chronic anemia have lower hematocrits (volume of red blood cells in blood total) than those suffering acute anemia or sudden blood loss. The normal hematocrit level is around 30-50%. This means cats with chronic anemia will need a transfusion if their hematocrit levels are around 10-15% and other cats with 20-25% will also need one.

Along with the hematocrit levels, there are other clinical signs which means the cat will require a blood transfusion. These symptoms indicate there is cellular hypoxia (low oxygen in cells) and include:

• Tachypnea (abnormally rapid breathing)
• Tachycardia (abnormally rapid heart rate)
• Weakness
• Stupor
• Increased capillary filling time
• Elevated lactate in blood serum

In addition to determining the recipient's blood group for compatibility with the blood donor, the donor cat must have been checked for any of the following pathogens or infectious diseases:

• Feline leukemia
• Feline immunodeficiency
• Mycoplasma haemofelis
• Candidatus Mycoplasma haemominutum
• Candidatus Mycoplasma turicensis
• Bartonella hensalae
• Erhlichia sp.
• Filaria sp.
• Toxoplasma gondii

Blood transfusion from cats with blood type A to blood type B

A transfusion of blood from a cat with type A blood to a cat with type B is physically devastating. As we have discussed, group B blood has strong antibodies against group A antigens. This leads to the transfused red blood cells to be rapidly destroyed (hemolysis) causing an immediate, aggressive, immune-mediated transfusion reaction which ends with the death of the cat.

Blood transfusion from cats with blood type B to blood type A

If the transfusion is performed conversely from a cat with type B blood to a cat with type A, the transfusion reaction is mild. However, the transfusion is till not effective due to the reduced survival of the transfused blood cells. A second transfusion of the same blood type can cause a much more serious reaction.

Blood transfusion from an A or B cat to an AB cat

If type A or B blood is transfused to an AB cat nothing should happen, since it does not have antibodies against group A or B.

Isoerythrolysis or hemolytic anemia is a disease which can affect newborn kittens. It is caused by the mother passing on antibodies which are incompatible with the kitten's blood type. These antibodies can be passed on to the ktitens through the colostrum, the first milk fed to kittens by their mother. The same problems seen in tranfusions can occur.

The most common incidences of isoerythrolysis occur when a female cat with type B blood crosses with a male cat of type A or type AB. Due to the recessive B allele, the kittens are mostly A or AB. When they suckle from their mother during the first days of life, they absorb numerous anti-type A antibodies which trigger an immune-mediated reaction. This causes red blood cell destruction (hemolysis) known as neonatal isoerythrolysis.

With neonatal isoerythrolysis caused by anti-type A antibodies, the kitten will usually die. If they ingest other antigen antibodies, the kitten will not necessarily die, but it will depend on how much is transferred. Isoerythrolysis does not appear until the kitten ingests these antibodies from the mother, so at the time of birth they are healthy and normal cats. Once they have taken the colostrum, the problem occurs.

Symptoms of neonatal isoerythrolysis in cats

In most cases, these kittens will weaken over time. They will stop suckling and become very weak and pale from the anemia. If they don't die, their skin and mucus membranes will become jaundiced (i.e. turn yellow). Their urine will also turn red due to the breakdown of hemoglobin.

In some cases, the disease can cause sudden death in infant kittens without symptoms occurring. In other cases, the symptoms are milder, but the tip of the cat's tail may darken due to necrosis.

The differences in severity of the clinical signs depend on the variation in the anti-A antibodies that the mother has transmitted from the colostrum, the amount of it that the kittens have ingested and their ability to absorb them due to the organism of newborn kitten.

Treatment of feline neonatal isoerythrolysis

Once the antibodies have passed to the kitten, they cannot be taken away. However, if the caregiver notices the problem during the first hours of life, they can remove them from feeding from their mother. They can then feed them with artificial milk formulated for kittens. This will prevent the kitten from ingesting more antibodies which would further aggravate the problem.

Prevention of neonatal isoerythrolysis in cats

Since treatment is practically impossible, it is important we do what we can to prevent feline isoerythrolysis. For this to occur, we need to know the blood group type of the cats. However, this can be difficult since many cats have unexpected pregnancies. Responsible breeders will know not to breed cars with incompatible blood types. This is one of many reasons we encourage the neutering or spaying of cats.

If the cat is already pregnant and we have any doubts about their care, we need to prevent the cats from taking colostrum during their first feeding. Although in almost all circumstances, the kittens need to be kept with their mother, a potentially lethal antibody transfer is one of the few cases were it is appropriate. However, we can also test the kitten's blood with the blood cards and determine whether this is appropriate. In these cases, the cat can be returned to their mother.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

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