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FELINE LEUKAEMIA VIRUS (FeLV)
Note for Pet Owners:
This information is provided
by Provet for educational purposes only.
You should seek the advice
of your veterinarian if your pet is ill as only he or she can correctly
advise on the diagnosis and recommend the treatment that is most
appropriate for your pet.
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Description
Cancer is one of the most common causes of death in cats and feline leukaemia
virus (FeLV) is responsible for approximately 33% of all feline cancer-related
deaths. In addition, many other cats with FeLV die from infectious diseases that
they are unable to overcome because of immunesuppression caused by the virus.
Cause
The causative agent is feline leukaemia virus (FeLV) an oncornavirus
belonging to the retrovirus group. It consists of a single strand of RNA
protected by an envelope. Based on nucleotide studies it is believed to have
evolved from a virus prevalent in an ancestor of the rat.
This virus does not kill cells that it infects, and it replicates by
budding. During budding the viral particles assume some host antigen and so
are protected from the hosts immune system because they are recognised as
"self". The bone marrow, salivary gland and epithelium of the
respiratory tract are just some of the tissues in which this virus can
replicate.
Signs
Initial signs of FeLV infection include:
Later signs include :
- weight loss
- recurrent infections
Complications
There are numerous complications and sequelae following infection with FeLV
including :
a) The development of cancer - lymphoma - often involving the intestine or
the thymus region of the chest b) Cancer of the blood cells (Leukaemia)
- white cells and red cells c) Anaemia due to bone marrow suppresssion d)
Reproductive abnormalities - including infertility, abortion, resorption e)
Osteochondromas (cancer of cartilage)
Transmission
Close contact is needed and transmission from one cat to another occurs
mainly via saliva. Apparently healthy cats can live for years and yet have
FeLV virus in their blood (called viraemia) and shed virus all the time. Other
routes of transmission are much less likely - in urine, faeces, other
secretions , via flea bites, from contaminated hypodermic needles, surgical
instruments, blood transfusions, infected environmental materials because in
the environment the virus only survives up to 48 hours.
Feline leukaemia virus is not highly contagious , so infected individuals
can be kept in a hospital environment - provided direct contact with other
cats is prevented, and reasonable hygiene is practices - such a snot sharing
feeding utensils, and washing hands by personnel after handling each
individual cat.
Transplacental transmission does take place , and transmission can also
occur in the immediate post-natal period when the infected queen grooms them.
Kittens are more susceptible to infection than adults.
Diagnosis
Any cat with enlarged lymph nodes (lymphadenopathy) should be tested to see
if it has feline leukaemia virus.
One of the viral core proteins p27 is produced within infected cells and this
protein is used in fluorescent antibody tests and ELISA tests to detect the
presence of the virus.
Feline oncornavirus cell membrane antigen (called FOCMA) is present on
malignant cell membranes but not other cells. Hence, cats with high FOCMA
antibodies are resistant to the development of leukaemia and lymphoma - even if
they are infected with the FeLV virus.
Treatment
Prevention Routine vaccination is available and recommended for cats that are in
regular contact with others. Provet comment :
Expert committees have designated FeLV vaccines as non-core HOWEVER Provet does
not agree with this categorisation. Although not highly contagious vaccination
has significantly reduced the incidence of FeLV-related cancers in young cats
since the 1970's and Provet does not wish to see a return to those days, and
vaccination is safe and effective.
There is no specific treatment for cats infected with leukaemia virus.
Supportive therapy is often helpful in providing an increased quality of life .
However, treatment is controversial in confirmed cases because FeLV can be
transmitted to other in-contact cats.
Prognosis
Always guarded, and often poor.
Long term problems
Updated January 2016
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