Neonatal isoerythrolysis is an immunologic, genetic neonatal illness seen only in felines. Kittens with blood type A or AB, born to blood type B queens have naturally circulating anti-A alloantibodies in the blood, which are passed to the infant through the first milk colostrum. The kitten appears healthy for the first 48 hours of life, but after suckling the mother’s milk, type A or AB kittens will progressively develop clinical signs of disease. Neonatal isoerythrolysis is a life-threatening disease, but if recognized within the first few hours of life, the kittens can have a higher chance of survival. 

Neonatal isoerythrolysis in cats is a serious, life-threatening condition seen in kittens born with a different blood type than that of the mother. The kitten will appear overall healthy at birth, but soon become ill after suckling the mother’s colostrum. The first milk supply is rich in antibodies to provide immunity against disease to the kittens. Cats cannot develop alloantibodies to collaborate with a separate blood type, so if the father to the kittens has a different blood type than the mother, the antibodies will not coincide with one another. Neonatal isoerythrolysis has a high mortality rate, which requires urgent medical treatment from a veterinary professional. 

The kitten affected with neonatal isoerythrolysis will appear healthy at birth, but progressively deteriorate after suckling the mother’s colostrum. The severity of the symptoms a newborn will display varies depending on the amount of antibodies said infant absorbed during suckling. The kitten will begin to fade over the next 48-72 hours, will stop nursing from the mother, weaken, and may develop jaundice. 

In other cases, the kitten may only be mildly affected by the alloantibodies and the antibodies prevent normal circulation in the kitten’s body. Clinical signs of a kitten partially affected by neonatal isoerythrolysis include the gradual dying of the ear and tail tips. 

Neonatal isoerythrolysis in cats is caused by incompatible blood type and alloantibodies between the mother and offspring. The condition is dependent on the genetic formula passed down from the parents, as blood type B cats possess strong antibodies against type A blood cells. 

Neonatal isoerythrolysis is diagnosed based on the litter’s presenting symptoms and laboratory data. The veterinarian will ask you about the parents of the litter. If your female cat participated in a controlled breeding program, it is important to bring that information with you to the appointment. If you do not have any information regarding the reproductive partner of the queen, the veterinarian will proceed to the following examinations:

If the mother has ever donated blood, had a blood transfusion, or if you have requested information regarding the blood type, this information will be present in the feline’s record. 

A coombs test detects antibodies against the red blood cells the feline possesses in the blood serum. 

A feline’s red blood cells will clump together due to the surface being covered with antibodies (persistent autoagglutination)

Treating neonatal isoerythrolysis once the kitten has absorbed the queen’s antibodies, is difficult. If recognized early, the kitten can be removed from the mother to avoid further absorption of the incompatible anti-A antibodies. The kittens will need to stop nursing the mother’s milk and be given a replacement milk formula for kittens. In other cases, the veterinarian may perform a blood transfusion with washed blood. In other words, the serum component of the transfused blood containing alloantibodies will be removed. The blood transfusion will encourage the kitten’s body to make antibodies against the incompatible blood type after approximately three days. 

The prognosis for neonatal isoerythrolysis in cats is guarded, as the condition is often caught too late. If the condition is caught early and the kitten has not absorbed a great amount of the mother’s alloantibodies, the infant may have a positive prognosis. The fact that kittens, especially newborns, are at such a vulnerable stage in life makes a positive prognosis difficult to obtain. To prevent neonatal isoerythrolysis from occurring, always control your feline’s breeding program to ensure a compatible male fathers the offspring. Felines that are not part of a controlled breeding group should be spayed.