FELINE LEUKEMIA VIRUS VACCINATION
Feline Leukemia Virus (FeLV) was one of the leading causes of death in cats until the
development of a vaccine in the mid-1980’s.
What is Feline Leukemia Virus (FeLV)?
Feline leukemia virus (FeLV) is one of the most important viruses infecting cats. FeLV tends to
become a persistent infection and depresses the immune system of cats. FeLV is an important
cause of anemia in cats and can cause cancers of several types.
How common is FeLV?
FeLV infection is found worldwide. Because cats become persistently infected and may carry the
virus for long periods before showing any clinical signs, your cat may be exposed to FeLV without
you realizing it.
What diseases does the virus cause?
FeLV invades and replicates in various cells of the cat’s immune system and blood-forming cells, as
well as other cells. The results include suppressed immune responses making the FeLV-infected
cat more susceptible to chronic or recurrent infections. Death or dysfunction of infected cells may
give rise to enteritis (inflammation of the intestine) or anemia (low red blood cell numbers). FeLV
infection can also change the genetic code in infected cells. The genetic code programs the cell’s
functions. Changes in genetic code as a result of FeLV infection may sometime later give rise to
cancers such as leukemia, lymphosarcoma or other tumors. These tumors may affect one or many
tissues, organs or body sites.
FeLV is usually fatal. Studies have shown that 80-90% of FeLV-infected cats will die within 3 to 4
years of the initial diagnosis.
Is there any treatment for FeLV infection or disease?
There is currently no specific treatment for FeLV-infected cats. Treatment is usually aimed at easing
the symptoms and treating secondary infections. Most FeLV-infected cats will eventually die of
diseases related to their infection or require euthanasia.
Is there a test for FeLV infection?
Special blood tests have been developed. Most tests are designed to detect the presence in the cat’
s blood for components of the virus. In general the test is very reliable although occasionally a
misleading result occurs. In some situations it may be necessary to confirm infection with the virus
through repeated blood testing.
Does my cat need to have a blood test before vaccination?
For the vast majority of cats, this is highly recommended. Remember not all FeLV-infected cats that
blood test positive become sick. Some FeLV-infected cats may not show signs of disease for
months or even years.
How safe is the vaccine?
FeLV vaccines have been specially developed so that they do not contain any infective virus
material and they are considered very safe. You are unlikely to see any ill effect of the vaccine apart
from some mild sluggish behavior a day or two after the vaccine is given. A very few cats may have
a mild allergic reaction. Most vaccine reactions occur almost immediately and your veterinarian will
provide appropriate treatment. If you are concerned that your cat is experiencing an abnormal
reaction in the hours or days following any vaccination, please call us.
How effective is FeLV vaccination?
FeLV vaccines have now been available for many years and they have been continuously improved.
They are clearly helpful in preventing infection with FeLV and thus controlling FeLV-related disease.
Unfortunately, no vaccine is 100% protective. Where possible do not allow your cat, particularly a
kitten, to come into close contact with known FeLV-infected cats or cats of unknown vaccination
history.
How often is revaccination necessary?
Revaccination is necessary in the initial course of vaccines to provide strong lasting immunity. Even
so, immunity does decline over time and your veterinarian will advise you of the recommended
revaccination schedule for your pet.

Animal Hospital of Fate 1001 North W.E.Crawford (Highway 66 in Fate) Rockwall, Texas 75087 972-722-0066
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1001 North W.E.Crawford (Highway 66 in Fate) Rockwall, Texas 75087 972-722-0066
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The Staff of the Animal Hospital of Fate
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