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Determining your cat's blood type

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As with people, there’s a good reason to know your cat's blood type, especially if it's intended for breeding, and even more so if it's an exotic breed. Some blood types are incompatible, and mixing the two can result in death.

There are three feline blood types: type A, type B and the rare type AB. In the United States, 95 percent of domestic cats are type A. However, in pedigreed cats, the frequency of type B blood varies greatly from breed to breed. Type A blood and type B blood are incompatible with each other, and severe reactions occur when the two are mixed either through transfusion or mating.

Transfusion risks

Cats with type B blood can die if they are given a transfusion with the common type A blood and vice versa. So, knowing a cat's blood type in case of an emergency can save precious seconds and possibly its life.

Mating risks

Blood type incompatibility is extremely important to breeders of pedigreed cats. Specifically, type A blood is dominant over type B, meaning that the kittens of a type B female bred to a type A male will usually have type A blood. When these type A kittens begin to nurse from their type B mother, she passes her anti-A antibodies to them through colostrum, or "first milk."

The mother's antibodies attach to the kitten's red blood cells, causing their destruction. A high percentage of these kittens will die suddenly after nursing from neonatal isoerythrolysis (NI), a common cause of fading kitten syndrome.

A breeder's story

Linda Smith of Nova Scotia, a former breeder of Cornish Rex cats, experienced this problem first-hand when she purchased male and female cats of different blood types.

“The first and second queens I purchased were both blood type B, but the first stud I acquired was blood group A,” Linda said. “I didn't know this at the time because the male's breeder didn't routinely type her cats.”

Linda, also a registered nurse, was acutely aware of blood incompatibility in people, and “figured that if humans can have blood problems, why not other mammals?” She had her male cat typed, although at the time it was simply for her own information, not because she was aware of feline NI. Luckily, she had a veterinarian who was, and it was her vet that told her not to let the kittens nurse from their mother for 48 hours.

“When my first litter was born, I removed the first four kittens to a heated box/bed,” Linda said, “but the look on the momma cat's face was something I'll never forget, and out of pity I left the fifth kitten with her, unsure of the outcome. As it turned out the kitten was fine so it must have been type B like its mom.”

Over the next two years and several litters, Linda routinely separated kittens and mother for the required time, and never lost a single one. Subsequently, she purchased only type B studs, double-checking their blood type when they had their first vet visit.

Symptoms of neonatal isoerythrolysis

In cases of NI, kittens are born healthy and appear vigorous at birth because they haven't yet been exposed to their mother's antibodies. Once they have nursed, kittens can suddenly die or become ill. Symptoms include:

  • Jaundice
  • Reddish/brown urine
  • Tail tip necrosis
  • Respiratory difficulty
  • Lack of nursing activity
  • Failure to thrive

Forewarned is forearmed

It is very difficult to save kittens once they develop NI symptoms. Transfusions sometimes work, but the best treatment is prevention – simply avoid mating cats with incompatible blood types by having them tested before mating occurs.

If an incompatible mating should happen, remove the kittens immediately and hand feed for two days. After that time, kittens may be safely returned to their mother since anti-A antibodies in the milk can no longer be absorbed by the kittens’ intestines.

Owners have an obligation to oversee breedings, especially when it comes to mating the more exotic pedigree. Taking the initiative to know a cat's blood type will go a long way toward promoting and protecting the health of cats and their kittens.

Credit: Reviewed by Amy I. Attas, V.M.D.
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