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Neonatal Isoerythrolysis in Kittens

Neonatal Isoerythrolysis is a fatal condition in which the antibodies in a mother's milk destroys the baby's red blood cells. This is caused by an incompatibility between the mother and baby's blood types.

Cats have the AB blood type system. They can have Type A, Type B or Type AB. Type A is the most common in cats, and Type AB is rare. When breeding, it is important to know the blood types of the parents, which breeds are most at-risk, and which blood type is dominant. The A is dominant over the B. Type A is dominant over AB, and B is co-dominant to AB.


Issues occur when Type A or AB kittens are born from a Type B queen. The colostrum from B queens contains antibodies against Type A blood, and the red blood cells (RBCs) of the kittens are quickly attacked by these anti-A antibodies.


The severity of the condition is dependent on the amount of colostrum antibodies the kitten consumes in first 24 hours. Kittens that nurse little in the first 24 hours see a subclinical course, with kittens sloughing the tip of their tails but often surviving. The gut closes to absorption of colostrum antibodies between 16 and 24 hours. At 24 hours old, the kittens digest the proteins and antibodies, further limiting the issue.

Type A kittens that nurse large amounts of colostrum from type B queens can quickly get into a life-threatening issue. Kittens usually die suddenly without signs after nursing the first meal because of how quickly the RBCs are attacked. If they survive, dark urine (pigmenturia) develops first, then anemia, jaundice and unthrifty kittens that are reluctant to nurse. Severely affected kittens rarely survive one week. This condition is a rule out for any fading kitten issue.


Because of the speed from onset to death, treatment of affected kittens is rarely successful. A blood transfusion along with feeding a milk replacer and giving supportive care can be attempted.


  1. The issue can be averted by testing and breeding Type B queens only to Type B toms. Commercial card tests are quick and available. (Siamese cats and related breeds, Tonkinese, Oriental Shorthair, Burmese and American Shorthair have only blood Type A.)
  2. For at-risk kittens: Foster Type AB or A kittens onto Type A queens or feed a commercial milk replacer for 24 hours to avoid the issue. Commercial milk replacers speed the closure of the gut to proteins (antibodies) and in 24 hours, the risk is minimal for antibody absorption. The 24-hour-old kitten develops the ability to digest the large protein antibodies, rendering them harmless.
  3. Kittens can be blood typed from a drop of umbilical cord blood or jugular stick, allowing Type B kittens to be left with their Type B mom. Type A can then be managed as above.
  4. In a cattery, colostrum antibodies are not essential to the survival of the kittens. At-risk kittens that are removed and fostered for the first 24 hours can be given 1-2 cc of serum from a Type A mom either intraperitoneally or subcutaneously to replace antibodies missed from mom's colostrum.

Knowing your breeding adults' blood types, as well as the risk in your breed, is essential in managing away from blood-type kitten loss. When the risk is present, preventing the Type A kittens from nursing the Type B mom for 24 hours usually solves the issue.

If you need help, call us at 1-800-786-4751.

-Dr. B
Don Bramlage, DVM, Director of Veterinary Services at Revival Animal Health

The materials, information and answers provided through this website are not intended to replace the medical advice or services of your personal veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.

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