Feline leukemia is a common diagnosis in cats. Veterinarians run hundreds of thousands of quick blood tests for this disease daily in vet offices around the world.
This post is an overview of the disease that answers the most common questions cat owners have about this condition.
Disclaimer: All content and information on this website are for informational and educational purposes only and do not constitute veterinary medical or pet health care advice.
What is feline leukemia and what causes it?
A virus called Feline Leukemia Virus (FeLV in short) causes feline leukemia.
Is feline leukemia a cancer?
While not a cancer itself, this virus is the most common cause of cancer in cats. It frequently causes lymphoma – a cancer of the lymphatic system that can affect multiple organs such as the eyes, stomach, intestines, kidneys, and many others.
How common is feline leukemia?
Cat leukemia is a very common disease. Although, on average, it affects less than 5% of the feline population (2-3% in the US and Canada), the percentage is much higher in some countries (up to 25% and more).
The risks of getting the disease are higher in free-roaming cats, especially those that can get bitten in fights, as well as in ill cats.
How is feline leukemia transmitted? How does a cat get it?
Infected cats transmit FeLV. The virus spreads mostly by saliva during close contact between infected and non-infected animals.
Cats mostly get it during cat fights, grooming, and mating. Female cats can pass FeLV to kittens during pregnancy or while nursing them.
How do indoor cats get feline leukemia?
Indoor cats are at much lower risk of getting the disease. If your cat tested negative (no disease detected), lives alone and does not go outside nor have contact with other cats – veterinarians will consider them a low-risk.
Indoor cats can still get FeLV from their FeLV-positive mothers, infected cats that live with them, or through encounters with neighbors’ cats.
Is feline leukemia contagious to cats, dogs, or humans?
FeLV is contagious to other cats. Although, it is not contagious to humans. Dogs cannot catch it, either.
How long does FeLV live on surfaces?
FeLV does not live long on surfaces. Researchers estimate that this time is around a few hours.
Can a cat with feline leukemia live with other cats?
The short answer is “yes”, even though the disease is contagious to other cats.
Very close contact is usually needed for FeLV transmission, and precautions can be taken to prevent it.
Please read our post on how to care for a cat with feline leukemia for detailed advice on what to do if you already have other cats at home.
In a situation when a FeLV-positive cat is being put up for adoption, it is generally recommended to find a home with no other cats.
What are feline leukemia stages?
Feline leukemia can progress in three different ways.
Abortive
Some cats clear the disease after the initial infection. Most owners will never know that their cat had the virus because common FeLV tests will be negative later. This is an abortive infection.
Regressive
Other cats will have the initial viremia (that is, having the virus in the blood) but will then go into so-called regression, clearing it from the blood.
They will stay permanently infected, but common tests used at veterinary offices will not show it as they check for viral particles in the blood.
Such cats are not a source of infection for other cats, but veterinarians cannot use them as blood donors.
Cat with this type of immune response can live up to a normal life span. This is a regressive infection.
Progressive
Another form of the disease is progressive. This is the worst scenario and, unfortunately, the most common one in kittens infected by their mothers.
These cats are positive on common tests even with multiple tests weeks or months apart. They are contagious to others.
Their life spans can be shorter, although they can still live for a few years.
What are feline leukemia symptoms?
Symptoms of the disease can vary greatly.
Cats with abortive or regressive infection will commonly have no symptoms at all.
In cats with progressive infection, you can see a wide array of signs, including but not limited to:
- decreased appetite
- chronic weight loss
- fever
- enlarged lymph nodes
- inflamed and/or pale gums and mouth
- skin infections and poor coat
- signs of urinary, digestive, respiratory, neurologic, reproductive, and eye problems.
Many of the symptoms are due to immune deficiency. Cats with FeLV are prone to all sorts of infections as their immune system infected with the virus fails to protect them.
Other signs can be related to cancer (again, all sorts of signs depending on where the cancer is) or blood disorders (for instance, with anemia you might notice pale mucous membranes and general weakness).
End-stage feline leukemia symptoms can also vary depending on which exact problem is most prominent, whether it is cancer, anemia, or serious infections. Weight loss can become very apparent at that point.
What are FeLV symptoms in kittens?
Kittens born with an infection or those who get it while nursing can have symptoms similar to those of adult cats (please see above).
Unfortunately, feline leukemia in kittens is generally more aggressive than in many adults, and the life span of infected kittens can be significantly shorter.
Is feline leukemia painful?
The answer to this question depends on what exact problem or consequence your cat gets due to the infection.
Cats without symptoms can live a happy life with no signs of pain, while those with end-stage progressive disease can have multiple secondary issues, some of which might be painful.
Remember that cats are very good at hiding pain and disease. Even a slight change in behavior, as well as many other non-specific signs such as decreased appetite and weight loss, can be a sign of a problem.
It is a good idea to bring the cat to a veterinarian if you feel your pet experiences pain or you have noticed any other symptoms.
It is frequently possible to manage a cat with even a progressive disease and to provide them with a good quality of life without pain, at least temporarily.
How to test for feline leukemia?
To diagnose FeLV, veterinarians most often run quick blood tests.
If the test is done at the clinic, you will typically know the results before you leave the vet’s office. If the blood is sent to an outside lab, the result might come in 1-3 days.
It is not common to perform a feline leukemia test at home unless your cat’s veterinarian does house calls and draws blood at home.
There are different types of tests. Sometimes, veterinarians run several different types of tests to confirm the disease or determine the cat’s FeLV status.
Besides, veterinarians run tests before they vaccinate a cat or a kitten against feline leukemia.
In some cases, veterinarians repeat tests in 4-8 weeks. Most commonly, this happens when there is a strong suspicion that a cat could have been infected recently. That is because time will pass before we are able to detect the virus in the blood, and the early negative test can miss the right diagnosis.
Is there a vaccine for feline leukemia?
Yes, there is a vaccine, and veterinarians use it widely. Although it is not for every cat at every stage of life.
Feline leukemia vaccine cost is similar to the cost of other cat vaccines.
The vaccine schedule for an individual cat is up to your cat’s veterinarian, but the general recommendation is to vaccinate all kittens starting at 8 weeks, with vaccine boosters in 3-4 weeks and 1 year later.
After that, the vaccination might cease for low-risk cats and continue annually for cats at risk.
The vaccine schedule might differ depending on the situation, the age at which the first vaccine is given, and the housing type. It can also be different for cats used in breeding.
Is feline leukemia treatable?
Treatment generally focuses on managing FeLV-related conditions such as cancer, anemia, and infections, as well as relieving the symptoms.
Besides, a cat’s welfare is very important. Here is our post with useful tips on feline leukemia home care (such as whether to let your infected cat outside, what to feed them, and what symptoms to look for).
As of today, no specific antiviral medications are recommended or used widely due to the lack of evidence.
Still, there is ongoing research into the treatment of this disease, and drugs such as zidovudine, raltegravir, feline interferon, and others are being studied and used by some veterinarians.
Despite the fact that no cure for this viral disease exists currently, we encourage you to ask your cat’s veterinarian about all possible treatment options.
How long can a cat live with feline leukemia?
Cats with abortive and regressive infection have a normal life expectancy (unless regressive infection turns into progressive, which is rare but possible in some circumstances).
Cats with progressive infection have shortened life spans and, generally, do not survive longer than 2-5 years after the diagnosis.
When to euthanize a cat with feline leukemia?
It is not recommended to base the decision on euthanasia solely on FeLV test results.
Some positive cats who were diagnosed with FeLV soon after infection can turn negative (see regressive infection) and live full and symptom-free lives.
Even those with a progressive infection can potentially live a few years of good quality life.
When your pet is at the final stages of feline leukemia, treatment does not bring any improvements, and you feel that your pet is suffering – discuss with your cat’s veterinarian end-of-life care and possible euthanasia.
FeLV and FIV (Feline Immunodeficiency Virus)
FeLV and FIV (also called feline AIDS) are two distinct retroviruses that have many similarities.
They both can cause cancer and immunodeficiency and in both diseases, infected animals frequently suffer from secondary infections.
Tests that check for both feline leukemia and FIV are in common use at vet offices. It happens sometimes that cats test positive for both diseases.
References
- The American Association of Feline Practitioners (AAFP). Feline retrovirus testing and management guidelines. Last accessed on February 14, 2024.
- MSD Veterinary Manual. Feline Leukemia Virus Disease. Last accessed on February 14, 2024.
- Cornell University College of Veterinary Medicine. Feline Leukemia Virus. Last accessed on February 20, 2024.