One of the more frustrating causes of neonatal kitten death is isoerythrolysis (NI). Frustrating because it can be prevented 100% once we are aware that the potential exists in our breeding cats.

NI results when two cats with differing blood types are mated and the kittens' blood type is not the same as the queen's. When the kittens nurse, especially the colostrum, they absorb antibodies against blood cells that don't match the queen's. The antibodies actively destroy the kittens' red blood cells causing severe anemia and toxic by-products from the degradation of the damaged cells.

In severe cases, the kittens can die within 72 hours of birth with little or no fore-warning. In less drastic cases, the kittens may not thrive as well as unaffected kittens, but still nurse and survive weaning, at which time they tend to rebound nicely. Some cases are so subtle that the only outward sign of the disease is the tip of the kitten's tail will die.

Besides the sudden death and severe anemia, the affected kittens can have kidney damage, blood clotting disorder, or other organ system failure. The first overt sign of a problem, aside from sudden death, is that the kitten stops nursing within the first 3 days. Other symptoms include a failure to thrive situation, dark, brown-red urine, and a jaundiced appearance to the nose and foot pads.

This condition is most common in pedigreed kittens. Some breeds are virtually one blood type, and so there is no risk of NI. Other breeds such as the Devon Rex and the British Shorthair can have 40% of the breed population be type B, with the other 60% type A. These are the largest at-risk populations.  Other susceptible breeds include the Cornish Rex (66% type A, 34% type B); the Scottish Fold and Sphinx (82% type A, 18% type B); and the Somali (83% type A, 17% type B).  It is vital to remember that other purebred cats can be susceptible to this disease, even if it is not common to that breed.  Owners should consult their veterinarian regarding an individual cat's susceptibility.

Luckily, with a little fore-knowledge, we can avoid the issue altogether. In breeds known to have type A and B blood, the queens and toms need to be blood typed prior to breeding. Breed only type A's together, and only type B's together.  Also, if you have a nursing mom who will foster kittens, you need to know her blood type so you don't inadvertently place kittens with potentially cross blood types on her to nurse.