Kittens born to an FIV mother will inherit her antibodies,
but not usually the virus.
A mother cat with FIV will have FIV antibodies which are
produced by her immune system in response to the virus.
When pregnant, she will pass these antibodies to her
kittens through the blood, but she will not pass the
virus, which will not cross the placenta.
Because the test for FIV actually looks for the antibodies
and not the virus, a kitten from an FIV mother will show
positive on the test without any virus being present.
As the kittens grow, they will gradually lose their
inherited protection, and will then test negative. This
can take several months, the actual time varies between
kittens, so any FIV positive test is not safe until the
kitten is at least six months old, and possibly older.
Kittens who really are FIV, are not common. The virus is
present in the milk, and yet it is rare that the kittens
actually get the virus from their mother (this also shows
how hard it is to transmit the virus across the mucous
membrane, indicating that the virus is not at all
We recently were in contact with a rescue group who
rescued 18 kittens from a farm colony - all kittens tested
positive for FIV. Later, the group tested them again with
a PCR test (which actually tests for the dna of the virus
itself) which showed that of the 18, only one was actually
infected with the virus.
If a kitten really is FIV, then it is thought that their
life may be shorter than most because they were infected
before their immune system was developed. However, we have
heard of FIV kittens that have not picked up general
sniffles and runny eyes when their non-FIV siblings have
done so, so we are not sure just how they are affected.