Feline Leukemia Virus (FeLV)
By: Michelle Young
All About FeLV
•Feline leukemia virus (FeLV), is a retrovirus.
•Retroviruses produce an enzyme, which permits them to insert copies
of their own genetic material into that of the cells they have infected.
•FeLV-infects cats worldwide, but the prevalence of infection varies
greatly depending on their age, health, environment, and lifestyle.
•In the US, approximately 2 to 3% of all cats are infected with FeLV.
How FeLV spreads
•Cats persistently infected with FeLV serve as sources of infection.
•Virus is shed in very high quantities in saliva and nasal secretions, but
also in urine, feces, and from mother to kittens.
•Transfer of virus may occur from a bite wound, and through the shared
use of litter boxes and dishes.
•However, the virus doesn’t live long in the environment, only a few
hours under normal household conditions.
What cats are at risk of infection?
• Cats that are exposed to other
infected cats; through bite wounds
or other close contact.
• Kittens are much more susceptible
to infection than are adult cats, and
therefore are at the greatest risk of
infection if exposed.
What problems can FeLV cause?
• Most common cause of cancer in cats
• Can cause various blood disorders
• Lowers the cat’s immune system so that it becomes
susceptible to other diseases.
• Bacteria and viruses that are found in the normal
everyday environment can cause severe illness in those
with weakened immune systems.
• The secondary infections are responsible for many of the
diseases associated with FeLV.
During the early stages there may be no signs of disease. Over time, the
cat’s health may progressively deteriorate or the cat may have recurrent
•Loss of appetite & weight loss that is slow in the initial stages of the disease but
can become more late in the disease process
•Poor coat condition
•Enlarged lymph nodes
•Fever that doesn’t go away
•Pale or inflamed gums
•Skin Infections, abscesses
•Urinary and upper respiratory infections
•Seizures or other neurological problems
•Problems with the eyes
Two Stages of Infection
•Primary viremia- the early stage of
infection. Some cats may have an effective
immune response & will be able to
eliminate it from the bloodstream
•Secondary viremia- later stage marked by
persistent infection of the bone marrow &
other tissue. If the infection gets to this
stage, most cats will be infected for the
rest of their lives.
Testing for FeLV
• Two types of FeLV blood tests are in common. Both detect
a protein component of the virus as it circulates in the
• ELISA -detects both primary and secondary stages of
viremia. Can be performed in vet’s office.
• IFA - test must be sent to diagnostic lab. IFA tests detect
secondary viremia only
How to protect cats from FeLV
The only sure way to protect cats is to prevent their exposure to FeLVinfected cats
Keep cats indoors
Keep uninfected cats separate from infected cats; don’t allow infected
cats to share food bowls or litter boxes with uninfected cats
Consider FeLV vaccination of uninfected cats. However, the vaccine
isn’t 100% effective
How to care for infected cats?
• Confine FeLV-infected cats indoors to reduce their
exposure to other infectious agents carried by animals and
to prevent the spread of infection to other cats
• Spay or neuter infected cats
• Feed well balanced, healthy diet
• Avoid raw feeding due to increased risk of bacterial or
How long can an infected cat live?
•Infected cats may remain in good health for many months
•Most cats die from an FeLV-related disease within two or
•If a cat has already experienced one or more severe illnesses
as a result of FeLV infection a much shorter survival time can
Feline Leukemia Virus
Facts about Feline Leukemia Virus
Feline Leukemia Virus or FeLV in Cats