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Feline Leukemia Virus (FeLV)

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What is FeLV?

The Feline leukemia virus is a virus that suppresses the immune
system and renders the cat more susceptible to other viral and
bacterial organisms as well as to some types of cancer. Signs of
infection can include: vomiting, diarrhea, weight loss,
decreased appetite, lethargy and anemia.

How could my cat get FeLV?

One of two ways:

1) the virus can cross the placenta and infect kittens of a FeLV
positive queen or shortly after birth, through nursing and
grooming.

2) a kitten or an adult cat can be exposed to the virus through
contact with other cats, either in a cattery or a multi-cat
household or by going outdoors. Exchange of body fluids,
especially saliva but also, feces and respiratory secretions, is
required for transmission of the virus. Thus, cat fights
resulting in bite wounds and sharing food and water bowls with
FeLV positive cats can put a FeLV negative cat at risk for
acquiring the virus.

What determines if my cat gets this virus?

If exposed, a cat may or may not become infected. This depends
on: 1) the cat’s immune system- in cases of stress (such as a
change in environment or introduction of another animal into the
household) or if the cat is young or already sick, it will be
more likely to become infected with FeLV.

2) the degree of exposure- if the cat receives a massive
exposure or if exposed over a long period of time, its immune
system may be overwhelmed and become infected with FeLV.

Testing for FeLV

It is important to test all cats for FeLV, especially cats being
newly introduced into a household. The virus is detected by
using a blood test (FeLV test). Tears and saliva can also be
used, but these tests are less sensitive in detecting the virus.

Negative results to the FeLV test means that the cat is not
shedding the virus. However, because there is a great deal of
variability between the time of infection and the time of
shedding of the virus, in some instances, a cat that tests
negative initially can test positive later.

Once a cat’s status has been determined, it can be vaccinated.
Depending on your cat’s lifestyle, vaccination for FeLV may or
may not be recommended. Cats that make no contact with other
cats are at very low risk of contracting FeLV. Thus, these cats
may not need to be vaccinated against FeLV. On the other hand,
cats that go outdoors and especially those that fight are at
high risk for acquiring the virus. If a cat tests positive,
there is no protection or harm by giving the FeLV vaccine.

Vaccination for FeLV

To start and complete the series of FeLV vaccines, 2 initial
vaccines are needed, 2-3 weeks apart. This is followed by
boosters every 1-3 years, depending on your cat’s risk of
exposure to FeLV.

While vaccination minimizes the chance of a cat contracting
FeLV, even a vaccinated cat can occasionally acquire the virus.
This can occur when the cat is unable to fully respond to the
vaccine or if an exposure to FeLV overwhelms the cat’s immunity.
Nonetheless, the vaccine does offer about 80% chance of
protection.

What does it mean if my cat tests positive for FeLV?

It means that your cat is infected and is actively shedding the
virus. When a cat is infected, it may:

1) Rapidly develop immunity and revert to a non-infected state
as it develops antibodies to eliminate the virus. For this
reason, if a cat tests positive for FeLV, it is recommended to
retest in 6-8 weeks to re-evaluate the cat’s status.

2) May be infected and continue to test positive with later
testing. It many not develop any signs of illness but may carry
the virus for an indefinite period of time. A healthy FeLV
positive cat may live out a normal life span with little medical
problems until late in life.

3) become ill soon afterwards with any FeLV-related disease

What if my cat tests positive but isn’t sick and what can I do
to help him/her?

If your cat tests positive for FeLV for 2 consecutive blood
tests but isn’t ill, the cat is still shedding the virus and is
infectious to other cats. Ideally, it should be kept indoors and
isolated from other cats. This not only helps to limit spreading
the virus to others but also protects the FeLV-positive cat
since its immune system is more susceptible to infections. This
includes taking the precautions of feeding and offering water
separately and washing hands after contact. Since the virus is
short-lived in the environment, thorough cleaning with most
common household disinfectants is sufficient to eliminate the
virus.

Without signs of illness, a FeLV positive cat can live a good
quality of life, but it does need to be protected against
stressful events and exposure to other cats and their illnesses.
Many experiments have been done with anti-viral drugs and
antibody therapy, but the results are inconclusive. Other
studies have shown that the administration of human interferon
as an oral solution on a daily basis to FeLV positive cats may
prolong survival. There are no negative side-effects, and it is
cost effective for long term use.

What if my cat is ill and how is FeLV treated?

While there is no treatment for the underlying FeLV virus, the
secondary FeLV-related conditions respond differently to
treatment. Supportive treatment including antibiotics, fluids
and blood transfusions can sometimes help FeLV positive cats
that are experiencing an acute illness.

In cases of FeLV-induced cancer, chemotherapy can sometimes
result in a remission of clinical signs for several weeks to a
few years. Chemotherapy can be effective in controlling, not
eliminating the cancer, and FeLV status does not appear to
influence a cat’s response to treatment. In most cases of FeLV,
however, the cat eventually succumbs to the disease.

What diseases can be associated with FeLV?

FeLV-related diseases include: anemia (low red blood counts);
leukopenia (low white blood counts); kidney disease; liver
disease; leukemias (cancer of the bone marrow) and lymphoma
(cancer of the lymph nodes). Lymphoma can result in cancer of
the lymph nodes in the mediastinum (in the chest) and mesenteric
region (in the abdomen); gastrointestinal tract (stomach and
small intestines) ; kidneys or spinal cord. Many diseases can be
indirectly caused by FeLV since it suppresses the immune system,
often resulting in chronic skin, teeth, gastrointestinal or
urinary tract problems.

What precautions should I take for my other cats if I have a
FeLV-positive cat?

For cats that have tested negative for FeLV but are living in a
household with a FeLV positive cat, it is recommended to
vaccinate the FeLV negative cats. The risk to the adult FeLV
negative cat of acquiring FeLV is 10-15% if they are exposed
several months to the FeLV positive cat.

Isolation of a FeLV positive cat in a multi-cat household is
recommended but is not always feasible. Keeping a FeLV positive
cat indoors will help limit the spread of the virus to other
cats and help protect that individual from exposure to other
cats’ diseases and bites. After the loss of a FeLV positive cat,
a prolonged waiting period is not needed before introducing a
new cat in the household.

Are there any risks to me?

No humans have been found to be infected with FeLV nor has any
case of human leukemia been traced to FeLV. FeLV does not appear
to be a human health hazard.

If you have questions regarding this disease and its treatment,
don’t hesitate to contact your veterinarian.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.