Feline Leukemia
There are many differing opinions about the Feline Leukemia virus, how it affects the infected Cats and what
should be done after being diagnosed. The article below explains what we believe to be the truth about the

Because Cats Vaccinated for the disease will test positive and the Tests are NOT 100% accurate, we do not
believe that Cats who appear healthy who test positive should be Euthanised. If the test comes back positive
for the disease, and the Cat appears healthy, they should be retested to insure an accurate Test result.

As explained in the article below, it is not always an immediate death sentence for a Cat who contracts the
disease. Because many Cats can live long healthy lives after contracting Feline Leukemia, we believe that
Euthanasia should be a last resort. There are many homes out there that already have ‘Leukemia kitties’ and
are willing to give a home to a new one.

Because Feline Leukemia is highly contagious, Cats with this virus need to be kept indoors at all times.
Contact with other cats may result in spreading the disease.  

Feline leukemia virus
From Wikipedia, the free encyclopedia

Feline leukemia virus (FeLV) is a retrovirus that infects cats. As a retrovirus, the genetic information of FeLV
is carried by RNA instead of DNA. FeLV is usually transmitted between infected cats when the transfer of
saliva or nasal secretions is involved, for example when sharing a feeding dish. If not defeated by the animal’s
immune system, the virus can be lethal.

The disease is a virus, not a cancer. The name stems from the fact that the first disease associated with the
virus was a form of leukemia. By the time it was discovered that the virus was not the same as leukemia, the
misnomer had already found its way into the vocabulary of pet owners.


Cats infected with FeLV can serve as sources of infection. Cats pass the virus between themselves through
saliva and close contact, by biting another cat, through a litter box or food dish used by an infected cat, and
from milk during nursing. Transmission can also take place from an infected mother cat to her kittens, either
before they are born or while they are nursing.

The virus can survive only about 2 hours in a dry environment, and about 48 hours in a damp environment
(such as a litter box)

FeLV causes immunosuppression in pet cats, and there is also evidence for existence of the virus in larger
wild cat populations also (e.g. lynx, cheetah, and lion). Overwhelming epidemiologic evidence suggests FeLV
is not transmissible to either humans or dogs.

Approximately 0.5% of pet cats are persistently infected with FeLV, but many more pet cats (>35%) have
specific IgG antibodies which indicate prior exposure and subsequent development of immunity instead of
infection. Transmission of FeLV is mainly via saliva and friendly behaviours, such as sharing feeding bowls
and mutual grooming (as distinct from fighting and biting).

There is strong evidence kittens under 4 months of age are more susceptible to infection, than are older
kittens and adult cats.

Kittens can be born with it, having contracted it from their mother while "in utero". Infection is far higher in
city cats, stray or owned, than in rural cats: this is entirely due to the amount of contact the cats have with
each other.

The disease has a wide range of effects. The cat can fight off the infection and become totally immune, can
become a carrier like a Typhoid Mary that never gets sick itself but infects other cats, or a mid-level case in
which the cat has a compromised immune system.

Four subgroups of FeLV exist: A; B; C, and T, but only subgroup A is transmissible between cats. The other
subgroups arise de novo and as results of recombination with an endogenous DNA feline sequence. Hence,
there is very good evidence this virus is quite ancient, and may well have evolved more than one time over the
last 10,000,000 years.


There are many possible outcomes as to how successfully the cat’s immune system will react to the virus.
About forty percent (40%) of cats extinguish the virus. Sixteen percent (16%) fight it off due to minimal
exposure to it. The other twenty-four percent (24%) resist the virus. All of this usually occurs between
sixteen to eighteen weeks after the FeLV infection begins. About twenty percent (20%) are able to put the
virus into a latent stage, in which the virus will remain until the cat becomes stressed causing the FeLV to re-
emerge. About five to ten percent (5% - 10%) of cats go through a sequestered stage in which viremia is
limited, intermittent, or absent altogether. Only about thirty percent (30%) of cats go through the disease from
start to finish, normally resulting in death.

Cats diagnosed as persistently infected by ELISA testing may die within a few months or may remain
asymptomatic for up to 4 years. The fatal diseases are leukemias, lymphomas, and non-regenerative
Anemias. Although there is no known cure for the virus infection, in 2006 the United States Department of
Agriculture approved Lymphocyte T-Cell Immunomodulator as a treatment aid for FeLV and/or FIV


Vaccines for FeLV are available, though no currently available vaccine offers 100% protection from the virus.
To help you protect
your Pet, we have added
information pages.

Topics can be found in
the links below:
Perry Animal Clinic