affected by neonatal isoerythrolysis may develop jaundice,
their skin to appear yellow
courtesy of Dr Urs Giger
are three feline blood groups: A, B and AB. Group A is the
most common, B is quite common in some breeds (see Table 1)
but is rare in others, and group AB currently appears to be
rare in all breeds.
group is determined genetically and the gene for group A is
dominant to the gene for group B. This means that a blood
group B cat must carry two group B genes (ie, it is homozygous)
and can only pass on a B gene to its offspring. A blood group
A cat may have two A genes (ie, it may be homozygous), or
it may have one A gene and one B gene (ie, it may be heterozygous).
A heterozygous cat will pass an A gene to around half of its
kittens, and will pass a B gene to the other kittens. This
means that if a heterozygous group A stud cat is mated with
a group B queen, a proportion of the resulting kittens can
be expected to be group A. Blood group AB is inherited independently
and the AB gene appears to be dominant to the B gene, but
recessive to the A gene.
A is generally the most common blood type. Blood type A and
B frequencies in domestic short- and longhair cats vary from
country to country; some countries have only type A cats,
whereas others may have as many as 50 per cent type B cats.
Furthermore, blood type frequencies vary between breeds; for
example the Siamese and some related breeds have only blood
type A, while other breeds may have as many as half and half
As and Bs (eg, Turkish Angora and Van).
group B cats all have naturally occurring anti-A antibodies
in their blood that are present in high levels from a few
months of age and which can cause destruction of type A red
blood cells. In the normal way this is quite safe because
group B cats do not have any type A red blood cells. However,
if a group B cat is given a blood transfusion from a group
A cat then the transfused A cells will be rapidly destroyed
and an immediate, dramatic, potentially fatal transfusion
reaction is likely to occur.
in the blood are also passed into the colostrum and milk,
so if a newborn group A kitten suckles from a group B queen
during its first day of life, it may absorb large amounts
of anti-A antibodies, causing damage to its type A red blood
cells – this is neonatal isoerythrolysis.
one third of blood group A cats have some naturally occurring
anti-B antibodies in their blood which will cause destruction
of type B red blood cells. In most cases the anti-B antibodies
are present in low numbers, enough to cause serious transfusion
reactions, but not enough
to cause neonatal isoerythrolysis.
blood group incompatibility
group incompatibility at birth, also known as 'neonatal isoerythrolysis'
or 'haemolysis of the newborn', can be a significant cause
of death in young kittens of certain breeds.
problem arises if a queen with blood group B produces kittens
that are blood group A or AB. The kittens are born healthy,
but during their first day of life they absorb antibodies
from the mother's colostrum (first milk) which destroy their
red blood cells causing anaemia and jaundice.
to look for in affected kittens:
kittens will all be normal at birth but, soon after they have
suckled, any group A or AB kittens in the litter may start
to show signs of disease. The severity of the signs is very
- In some cases neonatal isoerythrolysis
can cause sudden death, with no prior warning signs that
the kitten is affected.
- In most cases the kittens will appear
to 'fade' over the course of a few days: they will cease
suckling and become weak; they often appear pale and if
they survive may become jaundiced (yellow). They usually
pass red coloured urine due to the presence of red cell breakdown
products in the urine.
- Mildly affected kittens may show few
signs of illness during the first week of life, but the
tip of their tail may gradually die off.
- Some kittens remain unaffected and
show no signs of disease at all.
differences in the severity of signs are probably due to variations
in the amount of anti-A antibody the queen passes into her
colostrum; the amount of colostrum sucked by each kitten within
the first few hours of life; and the amount of antibody the
kitten absorbs from the colostrum.
of affected kittens
the kitten has absorbed the antibodies it is very difficult
to treat the problem.
- If the problem is recognised within
the first few hours of life the affected kittens must be
removed from the queen to prevent further absorption of
additional anti-A antibodies from the colostrum.
- It may be possible to give the kitten
a blood transfusion of washed red cells from a group B cat
(eg, the queen) in order to supply type B red blood cells
which will not be destroyed by the anti-A antibodies. However,
generally the problem is recognised too late for this to
be helpful, and there are very real, practical difficulties
in providing a blood transfusion to a newborn kitten.
the problem from occurring
treatment is rarely possible it is much more appropriate to
prevent the problem from occurring in the first place. There
are a number of practical measures that a breeder can use to
do this, as long as he/she knows the blood type of the cats
using group B cats for breeding altogether: This
approach certainly avoids the problem of neonatal isoerythrolysis,
but it may limit the choice of breeding animals, which may
be undesirable for other reasons particularly in small number
breeds with a high prevalence of group B individuals. This
approach will tend to reduce the proportion of group B cats
within a breed. It is only practical in catteries with no
other B cats, or in breeds where type B cats are rare.
mate group B queens with group B toms: This approach
will also avoid the problem of neonatal isoerythrolysis, but
again it will limit the choices for matings. All the offspring
of such matings will be group B so this approach tends to
gradually increase the proportion of group
B cats within a breed.
group A kittens from suckling colostrum from a group B queen
during first day: This method has been used by many
breeders, but does involve some risk of losing kittens to
neonatal isoerythrolysis (see 'Home Care' below).
typing for cats is now readily available. A blood sample can
be collected by your vet and submitted to a commercial laboratory
for testing, or the practice may have blood typing kits to provide a more immediate result. A number of these kits are now available providing an accurate and inexpensive means to blood type cats.
isoerythrolysis can be prevented if group A and AB kittens
are prevented from suckling colostrum from their group B
mother for the first 16-24 hours of life (the period during
which they are able to absorb antibodies from the colostrum).
blood typing kits are available then the kitten's blood groups
can be identified at birth, using a drop of anticoagulated
blood from each kitten (or its umbilical cord). In this way
only the group A and AB kittens need to be removed from the
queen, but any group B kittens in the litter can be left to
suck from the queen.
the kittens have been removed from the queen they must either
be hand-reared for the first 16 to 24 hours of life, or they
can be temporarily fostered onto a lactating group A queen,
if one is available.
- Hand rearing the kittens has
the disadvantage that the kittens miss out on the advantages
of receiving colostrum, but in most cases this does not
appear to cause clinical problems for the kitten except
in catteries with high risk of infectious disease.
- Fostering the kittens to another
group A queen will provide passive immunity to the kittens,
even if the foster queen is no longer producing colostrum.
Cats continue to produce relatively large amounts of protective
antibodies in their milk throughout their lactation, and
these antibodies will be absorbed by the newborn kittens,
giving them some early protection from infectious diseases.
no suitable foster queen is available, and the kittens are
considered to be at risk from infectious diseases that are
present in the breeding group, then some passive immunity
can be provided using serum harvested from a blood sample
collected from a donor cat. The blood sample must be collected
and separated by a vet, and the serum can then be fed to the
kittens or given by injection. While this is safe to do, it
rarely appears to be necessary.
1: Estimated frequency of type B cats in various breeds
NB: For some breeds only small numbers of cats
have been tested, so the figures may not be as accurate
as they would be if results were available for larger
numbers of cats. The proportion of group B cats within
a breed may change with time, depending on breeding
choices and patterns within that breed.
type B frequency
type B frequency
type B frequency (>25%)
Figures supplied by Dr Giger, University of Pennsylvania
Figures from a study of UK cats conducted by C Knottenbelt,
University of Glasgow
† Figures supplied by Dr Addie, University of Glasgow
** Figures supplied by Professor D Gunn-Moore, Edinburgh University
Urs Giger and Dr Diane Addie are internationally recognised
specialists in feline medicine who have a particular interest
in neonatal isoerythrolysis. Both have generously contributed
their expertise to this information
of the information reported here is based on original work
by Dr Giger's group. Dr Giger has a transfusion laboratory
where over 20,000 cats have been typed and many difficult
blood typing problems have been studied and difficult incompatibilities
have been reconciled. Dr Giger's web site is www.vet.upenn.edu/penngen
Diane Addie has also created a website which contains a lot
of information about this disease and she has established
a UK register of queens and stud cats of known blood groups
to assist breeders in managing this difficult problem. The
site is at www.catvirus.com
Updated November 2008