FeLV – Feline Leukemia Virus: Everything You Need to Know

Infection with FeLV, a feline leukemia virus, can affect cats. The infection is most often seen in cats that live close to each other. The virus attacks the bone marrow and the white blood cells.

Most cats with FeLV initially show no signs of illness. The asymptomatic stage can last anywhere from a few weeks to several years, before symptoms in the form of, for example, anemia or a weakened immune system appear.

It happens that the disease never breaks out in an infected cat, and it also happens that cats can get rid of the infection.


FeLV only spreads between cats and not to humans. Infection between cats can occur via urine, saliva and during mating, as well as through blood contact such as in connection with fights. Infection can also occur via food and water bowls.

FeLV can be spread from a pregnant cat to the fetus via the placenta and to kittens via the breast milk.


When symptoms appear, it can be in the form of weight loss, weakness, fever, dehydration, diarrhea, red eyes, enlarged lymph nodes, inflamed gums, fetal death and skin infections. Anemia is often seen, as is the effect on the white blood cells, which are important for the cat’s immune system. This means that the cat can become more susceptible to infection.


The diagnosis FeLV is made by detecting the virus in blood tests. This is done in a laboratory, but the actual blood sample is taken at the vet.


There is no real treatment for FeLV. Medicines that affect the cat’s immune system and prevent the virus from multiplying have been tried but without significant effect.


Cats that are diagnosed with FeLV should be kept indoors so that they do not transmit the infection to other cats, and to avoid the cat contracting other infections. The cat should be checked regularly by a veterinarian so that a possible flare-up of the infection can be detected in good time.

The virus has poor survival in the environment outside the cat, so a thorough cleaning is enough to remove the infection from the home. There is a vaccine against FeLV, which should not be used unnecessarily, as it may increase the risk of certain unusual tumor diseases. The vaccine against FeLV may have a worse effect in small kittens.

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