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FELINE LEUKEMIA VIRUS (FeLV) & FELINE IMMUNODEFICIENCY VIRUS (FIV)
Feline leukemia virus (FeLV) and feline
immundeficiency virus (FIV) are two important contagious viral organisms that infect cats. They affect the immune system and can cause
increased susceptibility to many diseases and cancers (especially lymphoma). FeLV infection is also associated with bone marrow
disorders and reproductive disorders. FELINE LEUKEMIA VIRUS
(FeLV)
Feline
leukemia is transmitted both from cat to cat and from mother to offspring. The most common
route of infection is through contact with infected body fluids (blood, saliva, etc.). Cats exposed to these viruses may 1) be able
to fight off the infection, 2) develop a hidden infection, or 3) become infected and
continuously infectious to other cats. Those
animals that have a latent or hidden infection cannot transmit FeLV to other cats unless
stress or immunosuppression (such as the administration of steroids) places the virus back
into circulation. Outside the cat, the
virus dies quickly in a dry environment. The
virus can survive twenty-four to forty-eight hours in a moist environment and so can
potentially be transmitted by sharing litter boxes and food dishes.
The
screening test for FeLV infection is a blood test called an ELISA antigen test. All positive tests should be confirmed with either
the submission of another more specific test called an IFA test or by repeating the ELISA
test in three to four months. To
confirm a negative test after exposure, an ELISA antigen test can be repeated in three
months. It is important to realize that cats
with latent infection test negative, but may still develop associated disorders later in
life. Vaccination does not interfere with
testing.
Feline
Leukemia vaccinations have been available for many years.
The vaccine is not one hundred percent (100%) effective. The vaccine has also been associated with the
development of an aggressive cancer at the site of vaccination called fibrosarcoma. The risk of vaccination should be weighed against
the risk of exposure and infection. If
vaccination is to be performed, test before vaccinating, as there is no benefit to
vaccinating a FeLV positive cat. FELINE IMMUNODEFICIENCY
VIRUS (FIV) There
are five different types of FIV: A, B, C, D
and E. In the United States, most cats are
infected with subtype A on the West Coast and B on the East Coast. The most common mode of transmission is through
saliva and bite wounds. The majority of
FIV-positive cats are outdoor males. FIV
survives outside the body for only a few minutes and is unlikely to be passed by sharing
litter boxes and food dishes. Most infected
cats will test positive within sixty (60) days after exposure. Kittens can test positive due to maternal
antibodies, but usually become negative later. Kittens
should be re-tested at six (6) months of age. FIV infection is associated with neurologic
disease, chronic renal failure, cancers (especially lymphoma), stomatitis (mouth and gum
disease), respiratory conditions, diarrhea, urinary disorders, and wasting syndromes.
Unlike the FeLV test, the FIV test is an
antibody test instead of an antigen test. The
viral antigen levels in FIV infection are usually too low to detect. Additionally, antibody levels wax and wane. They can be detected as early as two (2) weeks
after infection. IFA and ELISA are used as
the methods for the screening tests. FIV
negative cats are likely to be uninfected. A
Western blot test is the confirmatory test. Annual
FIV testing is recommended for at risk cats i.e., outdoor cats and those living with FIV
positive cats. An FIV vaccine has recently been developed. It is a killed vaccine composed of subtype A &
D. It is reported to be eighty-two (82%)
percent effective at preventing subtype A. There
are no data as to the efficacy against subtype B, which is the subtype found on the East
Coast. Vaccinated cats will test positive on
all tests including Western Blot tests. Vaccination
cannot be differentiated from infection on the FIV antibody test. Kittens from vaccinated queens can test positive
until eight (8) weeks of age. Only those at
high risk should be considered for vaccination and they should be tested negative
before. TREATMENT FOR FIV AND FeLV Treatment for FIV and FELV positive cats typically targets the treatment of the secondary diseases and supporting the immune system. Good nutrition and management are important components of therapy. Immunodulators such as the staphylococcal protein A, Acemannan, and interferon alpha have been used with varying degrees of anecdotal success. Antiviral drugs such as AZT are also available. Only the antiviral drugs have clinical data to support their efficacy but unfortunately have been found to cause adverse side effects. |
