A mother cat carries her litter normally and gives birth to a healthy litter of kittens. She cleans them, nurses them, cares for them but within a few days they have all weakened and died. This may happen litter after litter with the cattery breeder wondering what went wrong. While there are many reasons why newborn kittens might not survive, this particular condition is preventable.
Neonatal isoerythrolysis is a tragedy among breeders of kittens and is often written off as infectious disease, genetic defects, or simply natural selection. In fact, it is simply a matter of mismatched blood typing.
Many of us know our blood type: it is either A, B, O, or AB and comes with a negative or positive after it. It is the negative or positive that comes to be very important when it comes to HUMAN isoerythrolysis. The negative or positive in one’s blood type refers to whether one is negative or positive for a red blood cell protein called “Rh” factor, named for the Rhesus monkeys used in initial studies of this disease.
Problems do not occur when both parents are Rh positive or when both parents are Rh negative or even when the father is Rh negative and the mother is Rh positive. Problems occur with a very special combination.
When a man who is positive for Rh factor fathers a child with a woman who is negative for Rh factor, the child will be Rh positive. When the mother gives birth, her immune system becomes exposed to the baby’s blood. Her immune system mounts a response against Rh factor and soon she is armed with anti-Rh factor antibodies. This is not a problem for the first born child. It is the second child who is in danger.
When the mother is pregnant again with another Rh positive child, the antibodies of her bloodstream cross the placenta and destroy her unborn child’s developing red blood cells. The child will likely die. Luckily, this condition is preventable by first being aware of one’s Rh status when one becomes pregnant and by the administration of a product called RhIg when the first child is born. RhIg is an anti-Rh factor antibody that destroys any Rh factor entering the mother’s body at the time of the first birth. The Rh factor is destroyed before the mother’s immune system “sees it” thus preventing her from producing the antibodies that would attack her second child’s blood.
For more information on human Rh disease click here.
Cats do not have Rh factor but they do have A, B, and AB blood groups. Cats with type A blood are born with antibodies against type B blood; they do not have to have a blood transfusion or other blood exposure to develop antibodies. The same is true of cats with type B blood. They already have antibodies against type A blood.
Feline Blood Typing Test
(results are positive for type B blood)
In humans, a parental mismatch of blood requires two children, in order for problems to occur. This is because Rh negative women do not come with antibodies against Rh factor; they have to be exposed through childbirth (or a mismatched transfusion or other exposure to someone else’s blood) in order to make the killer antibodies. Cats come already armed, as it were.
So the problem results when a type B mother cat is bred to a type A tomcat. Type B feline blood is unusual in the mixed breed “domestic short hair population” where one can nearly count on a cat to have type A blood. In purebred cats, particularly Asian breeds, Type B blood is very common so if one is not careful, and does not type the cats to be bred, one is asking for trouble.
So the type B mother has a uterus full of type A kittens. The feline placenta does not allow antibodies to cross over and this is what is life-saving for the kittens, presuming the humans involved know what to do next. The litter develops normally and is born normally. It is with nursing that disaster strikes.
Colostrum is special milk produced by the mother of any mammal species for the first 48 hours or so. The first two days of life is extra special for baby mammals as this is the time when the mother gives a copy of her own immunity to her young. The milk produced in this period is rich with all the antibodies the mother has to give: vaccination generated antibodies, antibodies from exposure to all sorts of proteins she has experienced or infections she has survived, and, of course, antibodies against the “wrong” blood type.
The infant’s intestine is in a sensitive time during these couple of days. The antibodies delivered in the mother’s colostrum are not digested like regular proteins; instead, they are absorbed intact and provide the basis for the baby’s protection against infectious disease until the baby’s immune system is mature enough to make its own antibodies. After the first two days of life, the intestine achieves what is called “closure” and no more such absorption takes place. Any proteins that enter the GI tract are broken down as nutrients.
The type B mother cat is giving a great big dose of anti-A antibodies right into her kittens with her colostrum and the babies are absorbing it into their bodies. The antibodies destroy the kittens’ developing red blood cells, they get pale, perhaps even jaundiced. They get weaker and weaker and then they die, poisoned by their own mother’s milk.
As with human Rh disease, the first step in prevention is awareness. If one is going to breed purebred cats, have their blood types tested before they are bred. This can be done at the vet’s office with a test kit and can often be done “while you wait.” Ideally, a type B mother cat would only be bred to a type B tomcat.
So what do we do about the kittens already on the way? The key to survival is to keep the kittens from drinking their mother’s colostrum. As soon as they are born, they must be removed from the mother cat and either nursed by another mother cat or bottle-fed (see our page on Orphan Kitten Care for full instructions). They can be returned to their real mother after her colostrum production is over. This ought to be two days but keep them away for three days just to be sure. Regular mother’s milk is not a hazard as the antibodies will be digested by the babies.
As for the immunity lost by giving up colostrum, there is a next best thing: a plasma transfusion. Feline plasma of the correct blood type can be given to the kittens by injection. This blood product will contain many protective antibodies and none of the harmful ones. It is not as good as type matched colostrum, but is fairly available in most animal blood banks.
Neonatal isoerythrolysis is the condition in newborns where red blood cells are destroyed by the mother’s immune system. This is a preventable condition as long as blood typing is diligently practiced by breeders.
Page last updated: 8/18/10