Feline Leukemia Virus (FeLV)

Guest Post by Lorie Huston, DVM

Feline leukemia is a frequent worry for cat owners, regardless of the cat’s breed. This is because feline leukemia, or FeLV as it sometimes known, is a contagious disease that can be passed from cat to cat.

What Causes Feline Leukemia

Feline leukemia is caused by a virus in the class of viruses known as retroviruses. It is passed from cat to cat by direct contact with body fluids. Normally, close contact is necessary for the disease to be passed. Activities such as grooming, sharing food dishes, water bowls or litter boxes, fighting or playing can all spread FeLV.

Feline leukemia can also be passed from a pregnant mother cat to her kittens. It is one of the leading causes of “fading kitten syndrome.”

How Is Feline Leukemia Detected or Diagnosed?

Many cats that test positive for feline leukemia appear perfectly healthy and it is impossible to diagnose FeLV by simply looking at a cat. The most common means of diagnosing feline leukemia is with a blood test that tests for antigen to the feline leukemia virus. This test is known as an ELISA test.

Though the ELISA test can be performed on saliva and on tears as well as blood, blood test results typically result in fewer inaccurate results.

Testing is recommended under several circumstances, according to the AAFP (American Association of Feline Practitioners) Retrovirus Guidelines.

  • All kittens should be tested for feline leukemia, especially if their mother’s feline leukemia virus status is unknown.
  • Any cat new to a household should be tested for feline leukemia before being introduced to cats already in the household.
  • Any sick cat, regardless of previous feline leukemia virus status, should be tested.
  • Any cat for which vaccination against feline leukemia is being considered should be tested prior to vaccination.
  • Any cat exposed to feline leukemia should be tested.

What Happens if My Cat Tests Positive for Feline Leukemia?

One of three things can happen when a cat is tested for leukemia.

  1. He can test negative, which is the ideal situation and indicates he is not likely to be infected with the virus.
  2. He can test positive but be able to mount an immune response which is adequate to rid himself of the virus. In this case, a subsequent test will be negative.
  3. He can test positive but be unable to clear the infection. Subsequent tests for feline leukemia will remain positive.

If your cat does test positive for feline leukemia, he should be retested in 6-10 weeks. If he still tests positive, there is a good chance he has a persistent infection. There is another test, the IFA test, which is recommended to confirm infection in this case. This is done to rule out the possibility of a false positive ELISA antigen test.

Under rarer circumstances, a cat can harbor the feline leukemia virus in the bone marrow, appear perfectly healthy and test negative on both tests (or test positive on an ELISA test and negative on the IFA test.) For these cats, under conditions of stress, the virus can become active again. This is the reason that some breeders recommend testing cats used in breeding programs every 6 months. It is also the reason for recommending that any sick cat be retested for FeLV, regardless of the previous FeLV status.

If your cat does test positive for the feline leukemia virus and is healthy otherwise, there are several precautions which should be taken.

  • The cat should be housed indoors.
  • Have your cat spayed or neutered.
  • He should be housed separate from other cats or only with other cats that are positive for FeLV also.
  • Keep your cat up-to-date on vaccinations.
  • Keep your cat free of both internal and external parasites, such as fleas, ticks, intestinal parasites and heartworms.
  • Feed your cat a high quality diet. Raw diets may not be appropriate.
  • Monitor your cat closely for signs of illness. Any illness should be reported to your veterinarian immediately and should be treated aggressively.

Vaccinating Against Feline Leukemia

There is a vaccine available for feline leukemia which may be considered for your cat, depending on your cat’s lifestyle and risk of exposure.

  • Only cats which have tested negative for feline leukemia should be vaccinated. The vaccine will not protect a FeLV positive cat.
  • Only cats that are at risk of exposure to feline leukemia should be vaccinated. Cats that live indoors and whose risk is minimal do not need to be vaccinated. Vaccination may be considered for cats that spend time outdoors and are likely to socialize with other cats.
  • Some veterinarians recommend vaccinating all kittens for feline leukemia because kittens tend to be more susceptible to the disease than mature cats.

Symptoms of FeLV in Cats

Many cats that test positive for feline leukemia will appear perfectly healthy. However, when disease does occur, it can mimic many other feline diseases. The feline leukemia virus can cause a form of cancer but most frequently, it acts by suppressing the immune system, leaving the infected cat susceptible to secondary infections. Essentially, feline leukemia should be considered a potential cause for any sick cat until the blood testing has ruled out FeLV as the cause. Respiratory symptoms (sneezing, coughing, runny eyes, runny nose, etc.) are common with feline leukemia, as are symptoms such as weight loss, lack of appetite, fever and other signs of generalized illness.

Cats that test positive for feline leukemia but are otherwise healthy may remain so, sometimes for long periods of time. However, once symptoms of feline leukemia surface, the disease is difficult to treat and is most often fatal. Treatment is usually symptomatic and based on clinical signs, although various medications to boost the function of the immune system have also been tried with varying degrees of success.

Website | + posts

Hi, I’m Jenny Dean, creator of Floppycats! Ever since my Aunt got the first Ragdoll cat in our family, I have loved the breed. Inspired by my childhood Ragdoll cat, Rags, I created Floppycats to connect, share and inspire other Ragdoll cat lovers around the world,

Similar Posts


  1. Hi all I have a 4 month old kitten called lexi she’s recently been confirmed with feline leukemia so far she’s been herself she’s had the cat flue a few times but she is lively and playful what should I expect vet didn’t tell me much any info will be great

  2. The breeder we got our ragdoll from warned that ragdolls don’t respond well to the FeLV vaccine. Rupert tested negative but I don’t like that I’m not supposed to vaccinate him. Did anyone else’s breeders specify that a FeLV vaccine should be avoided? I just want to protect him in any way that I can. Any information would be helpful. Rupert is a year old and our only cat. He’s at a low risk I’d guess.

  3. Leslie Reader Hemme says:

    I have heard that a cat exposed to ANY virus can show positive on the test for up to 3 mo. but not actually have Leukemia.

  4. SharonAnn says:

    The best person to talk about this would be your vet. It is real hard for cat to get FeLV. Your cat would have to be around another cat who has FeLV and your cat would have been bit, srached or share water bowls with that cat who has FeLV. If you are boarding you little guy at the vets, I would think there is less to worry about. Vets are very aware which cat are sick and will not have you little Ragdoll around other cats that are sick.

    We have hired people to come in and once a day to come in and make sure our girl get food, water and a clean litter box. It does cost a little more, but she much happier in her own home.

    Worry less, just enjoy your kitty, love on him and have fun while on vacation.

  5. I am getting a Ragdoll and have been reading about Feline Leukemia. I have never had a Ragdoll but have always had humane society cats. We have always had them vaccinated for feline leukemia. I was not aware that there was so much controversy surrounding this vaccination. Now that I am getting a Ragdoll, though, I am really worried. My husband and I go on a weeks vacation once per year and have always boarded our cats at the vet. We never worried about FeLV because of their vaccination. I am worried now about boarding my Ragdoll at the vet while we are gone. I have no one to come in and look after him while we are gone. Do you think he will be fine? I really need advice on this. Thanks.

  6. Catlady1957 says:

    This Feline FeLV is very devastating and the information I have found on the internet has been mind bottling. My vet told me it is like distemper in puppies. My son brought a kitten in the home. She became quite ill all of a sudden. Up to that point she was thriving and doing well. All the kittens in that litter died. I have two female cats that are 2 years old. My one cat does have FeLV positive test. The other does not. They ate out of the same bowl, drank water from the same bowls, and used the same litter box. Both my cats are on Revolution, get vet care and have all their immunizations. Neither of my cats have been sick a day in their lives. I got these cats as kittens and have been well taken care of. I am hoping the immune system in my FeLV positive cat is strong. I know the other cat’s immune system has to be since she tested negative and was given the vaccine. My FeLV positive cat shows no sign of the illness. My hope is she will pass this virus and it won’t go into stage two. A mother cat can pass the virus to her kittens, a Bite wound. Why Chloe has tested positive is heartbreaking. Both my cats ate and drank from the same bowls.Used the same litter box, but only one cat tested positive for FeLV. My calico is a very loving cat and gentle cat. She sees my tears and tries to comfort me, but it is HER I am crying about and want to comfort her. I feel I am living a nightmare.

  7. SharonAnn says:

    Excellent article! My little Ragdoll is one of the cats that does harbor FeLV in the bone marrow. Breeders do need to be aware that just because the queen test negative for FeLV does not mean it is negative, if the viruses is hiding in the bone marrow. Breeders need to test the pregnant queens for FeLV, as stress of pregnancy can active the FeLV, which may spread to the kittens. Breeders should never let the kittens around other cats. Unless the breeder is a 100 percent sure the other cats in the colony are free of FeLV. Kittens under 6 months cannot fight off the FeLV viruses as well as older kittens.

    Everyone who owns a cat needs to careful when letting their cats outdoors; many feral cats do carry FeLV among other diseases. Unless cat is supervised outdoor, no one can be sure that their cat is not in contact with other cats who do carry the FeLV. Even if your cat is vaccinated for FeLV, the vaccine is only 80% affected.

    Sorry if I sounds harsh, but my little girl has been though a lot this pasted year and all of this could have been prevented with some awareness. Even good breeders can make mistakes, if they are not aware. Best way to avoid things like this is thou education.

    1. Catlady1957 says:

      You wrote an excellent article. I am truly sorry over your loss. I think like you cat breeder need to be aware of this virus, and my thought cat owners also.Know what exactly we are dealing with.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.