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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.


Feline leukemia is a concern for many cat owners. It seems most cat owners have heard of the disease but many do not fully understand how their cat can get feline leukemia or how it can affect their cat. Let’s talk a little bit about that.

What Is Feline Leukemia?

Feline leukemia is caused by a virus known as the feline leukemia virus, or FeLV. It is a contagious disease that can be passed from cat to cat through direct contact. Usually close contact with an infected cat is necessary for transmission of the virus. Casual contact is not typically dangerous. The virus can also be passed from a mother cat to her kittens.


What Kinds of Symptoms Are Seen with Feline Leukemia?

Some cats infected with feline leukemia will show no signs at all. When symptoms do occur, they can appear in almost any form. Common symptoms include lack of appetite, lethargy, fever, and weight loss. Respiratory symptoms such as coughing, sneezing, runny eyes, or a runny nose may be seen. Diarrhea and/or vomiting may be present. Some cats may be icteric (have yellow coloration in their skin and gums). Other symptoms may develop as well.

Essentially, any sick cat with an unknown feline leukemia virus status could be suffering from feline leukemia and testing should be performed to rule out the infection.

How Can I Tell If My Cat Has Feline Leukemia?

Blood testing is the only way to tell whether your cat is infected with the feline leukemia virus. A screening test requires only a few drops of your cat’s blood and usually can be performed in a matter of minutes. If the screening test is positive, your veterinarian may recommend further blood testing to confirm the diagnosis.

It’s a good idea for all cats to be tested for feline leukemia. Without a blood test, it is impossible to determine whether a cat is infected with FeLV. Seemingly healthy cats can test positive for the virus.

What If My Cat Does Test Positive for FeLV?

Knowing your cat’s feline leukemia virus status can ensure that adequate steps are taken to protect your cat’s health as well as the health of other cats. An otherwise healthy cat that tests positive for FeLV does not need to euthanized. However, it is important that positive cats be housed indoors. If positive, your cat should be kept current on core vaccinations such as rabies, feline panleukopenia, feline calicivirus, and feline rhinotracheitis. Take steps to keep your cat parasite-free. Avoid feeding raw food. Seek veterinary care immediately if your FeLV positive cat is not acting right.

How Can I Prevent My Cat from Getting This Disease?

There is a vaccination available that provides protection against feline leukemia. However, the vaccine is not a core vaccine and is not recommended for all cats. Only those cats whose lifestyle puts them at risk for infection should be vaccinated against FeLV. Cats that live indoors and are not exposed to other cats are not at risk for infection.

Some veterinarians do recommend vaccinating kittens against feline leukemia regardless of lifestyle because of the fact that kittens are more susceptible to infection than mature cats. However, this is not a universally accepted practice.

Dr. Lorie Huston

Image: Seiji / via Shutterstock

Comments  5

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  • Confirming FeLV
    02/04/2013 07:04pm

    " If the screening test is positive, your veterinarian may recommend further blood testing to confirm the diagnosis."

    Is it true that a cat can test positive for FeLV if it has been exposed, but doesn't necessarily have the disease?

    Also, I've heard that if two test in a row (from different batches) test positive, it's prudent to wait 6 months and then retest. Is that true?

  • 02/07/2013 11:37pm

    It is true that a cat can test positive for feline leukemia and remain healthy for a long period of time, sometimes eventually passing away of something completely unrelated to the virus. However, cats with positive tests should be considered carriers of the virus in the respect that they can potentially pass the virus to other cats.

    Different veterinarians have different testing protocols for confirming a feline leukemia infection. Some will wait and then retest after several months. Others will recommend a confirmatory test immediately. It depends to some extent also on the situation. Waiting to confirm infection might be more acceptable for a cat living alone and indoors in a single-cat household than a cat living with one or more cats in the same household.

  • 03/10/2015 05:51pm

    This comment has been flagged as inappropriate.

  • 02/08/2013 11:29am

    Dr. Huston,
    Thank you for this posting.

    Would you expand a little by what is "direct contact"?

    Also, what is feline calicivirus, and feline rhinotracheitis?

    Thank you!

  • 02/08/2013 06:32pm

    Hi Christine.

    Feline leukemia virus requires close contact with an infected cat to be transmitted. That's what I meant by "direct contact." Transmission may occur if saliva from an infected cat contacts the mucous membranes (i.e. the gums, eyes or nose) of another cat. It can also be passed through contamination with infected blood (or transfusion of infected blood.) Kittens can be infected by a positive mother during pregnancy also. Casual contact, like being near an infected cat without actual contact, will not spread the disease. It's important to know that many cats develop at least some immunity to the disease as they mature also. Kittens are the most susceptible to infection. However, that doesn't mean that an adult cat is always resistant to the disease. It depends on the cat, its immune status and its overall health.

    Feline calicivirus and feline rhinotracheitis are both respiratory viruses that affect cats. They are the two most common causes of upper respiratory infections. There are vaccinations available against both viruses. These viruses are usually combined with the feline panleukopenia (aka feline distemper) virus into one vaccine product.

    Please let me know if you have further questions and I'll be happy to answer them if I can.

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