Feline Leukemia Virus

Angela is a cat and dog lover who has made special efforts to learn as much as she can about the animals she cares for.

What Is the Feline Leukemia Virus?

The Feline Leukemia Virus, or FeLV, is a retrovirus found in cats. A retrovirus changes the genetic makeup of infected cells by reversing some of the genetic code, which makes their body more susceptible to infection and will eventually lead to death.

FeLV is transferred through bodily secretions such as urine, milk, feces, and saliva. Most often, cats transfer the disease by mutual grooming, nursing, or bite wounds. It also can be transmitted through sharing a litter box or a feeding dish, although this type of transmittal is much less frequent.

Two to three percent of all cats have the virus, and their life expectancy cannot be predicted. Like AIDS, there are two stages of feline leukemia. Primary and secondary viremia. Primary viremia is more similar to HIV, in that their life is not yet at risk, but will be if the disease progresses. A cat can stay in this stage for many years. Secondary viremia is when the bone marrow or other tissues are severely affected. Once secondary viremia begins, the disease will eventually take the cat's life.

Mucus Membranes of a Cat With the Virus

Symptoms of FeLV

The first sign of FeLV is no sign at all. A cat may appear to be very healthy for months or even years before they begin showing signs of the disease. Because they do not have immediate symptoms, they often have had a chance to infect many other cats by the time they are diagnosed. Once the disease has progressed, here are the most common symptoms:

  • Loss of Appetite: If the cat chooses not to eat at all, they may end up with fatty liver disease, which will eventually cause yellowing of their skin. If not treated, they will die of this disease, rather than leukemia.
  • Dull Coat: Due to their body's inability to produce healthy natural oils, or they may become very greasy due to lack of desire to clean themselves.
  • Weight Loss: This is often slow—unless they have stopped eating.
  • Pale Gums: An example of this can be seen in the photo above.
  • Infections: They can develop in the eye, urinary tract, skin, and upper respiratory system.
  • Lethargic Behavior: If you know the odd behaviors of cats, you may be wondering how can you determine lethargy in a feline. Although if you notice your cat has become increasingly lethargic, or a kitten, which should be curious and active, you may want to have your pet checked out.
  • Anemia: It is most deadly in kittens, is the number one reason young cats die of FeLV.
  • Stunted Growth in a Kitten: If you have a kitten in a litter that doesn't seem to be growing, most likely it has feline leukemia. Unless treated, its life expectancy will be very short.
  • Seizures: These are often due to neurological damage.
  • Persistent Fever
  • Persistent diarrhea
  • Tumors
  • Miscarriages

Healthy Kitten

FeLV in Kittens

Kittens, due to their size and age, are more susceptible to feline leukemia than an adult cat. Adult cats become infected 30 percent of the time when exposed to the disease, whereas a kitten becomes infected 100 percent of them by the same amount of disease. Therefore, even if your kitten was born to a healthy mother, it is crucial to protect them from becoming infected by keeping them indoors and away from known infected felines until they are full-grown.

Physical and Habitual Signs

Kittens who contract FeLV have a higher chance of early death due to their already compromised immune system. The most significant indicator that your kitten might be infected is if they seem lazier and not curious. They may also seem smaller and grow at a slower rate than an average feline of the same age.

Also, kittens with the disease tend not to want to eat, which is very dangerous because cats have a very ineffective liver. Often just a few days of going without food will severely affect their health. Any time your kitten or cat chooses not to eat even for a day or two, you should take them to the veterinarian immediately. Not only is it a sign that something bigger could be wrong, but unchecked, it can also result in liver failure, and eventually, death.

Treatment Options

There is no cure for FeLV, but there are things you can do to help your cat live longer:

  • Spay or neuter your cat to prevent further spreading of the disease. Also, pregnancy can adversely affect a cat that has FeLV. Not only is the chance of survival of the kittens low, but the pregnancy might become too much for the sick cat's body to handle. If they do get pregnant and the kittens survive, the chance that the kittens will have the disease is very high.
  • Feed them a nutritious and balanced diet, by providing a cat food that is high in protein. Avoid uncooked foods, because they will not be able to fight against food-borne illnesses that often result from uncooked foods.
  • Bring your pet to the veterinarian every six months, so the doctor can check for any infections that you may overlook. Also, notify the vet as soon as you see any changes in behavior or health.
  • Keep your pet indoors, which not only protects other cats but also protects your cat from getting any infections or diseases from other animals. Your pet will be very susceptible to even minor illnesses or infections. A minor infection that may cause diarrhea in a healthy cat may take an infected cat's life.

The Vaccine

The FeLV vaccine is a two-part vaccine. The first portion is best given to a kitten between the ages of eight and ten weeks; the second is given between eleven and thirteen weeks. Although, unlike many vaccines, it is not one hundred percent effective. The effectiveness is somewhere between 90-95 percent.

The vaccine can be given in two different ways. One is with a needle, another using VET JET, which is delivered with a burst of air by placing it in contact with the skin. Most vet offices use a needle since not all offices have a VET JET.

A Very Small Risk

There is a minimal risk of causing tumors, so the vaccine is usually given in the left-back leg. The reason they do this is that it makes the location site easy to monitor, in case a tumor does develop. Even if a tumor does grow, a cat can survive without the left-back hind leg. Although this risk is very slight. There is also an even smaller risk that the cat could develop the disease itself. Most vets do agree the benefits outweigh the cost, although you want to talk to your vet about your particular cat.

Marley Family Fund: Help Support Cats With FeLV



Questions & Answers

Question: How long will a cat live after they stop eating anything?

Answer: A cat can survive for about two weeks without eating. If a cat is not eating or drinking, though, they could only survive three days. Unfortunately, cats have very poor livers, and if they go for even a short amount of time without food, they can develop fatty liver disease. This is very hard to cure, and often leads to death.

© 2012 Angela Michelle Schultz

Angela Michelle Schultz (author) from United States on September 12, 2019:

I am so sorry Marsha. We have been there, it is so hard when a loved one is sick.

Marsha on September 08, 2019:

My cat is week eats a little his skin is yellow the vet said he has jaundice he looks really sick I cry every night she gave him meds to get him to eat and some pink stuff it begins with a b but so scared I'm going to wake up and his gone he also has felve I just hope the meds will work is there anything else I can do for him I love my baby so much it breaks my heart seeing him go through this

Steve on December 05, 2018:

I have a two year old cat named Larry I found him abandoned he has feline leukemia so sweet friendly and full of personality, he is very healthy but I dread the day this illness takes him from me I have other cats so I have to keep him in his own room so he can’t infect any of my other cats , I hope some day they find a cure

Angela Michelle Schultz (author) from United States on August 17, 2012:

I'll have to look into that. Thank you for bringing this to my attention.

bdrum11 on August 17, 2012:

I echo the other comments thanking you for writing this informative article. It's heart-wrenching to hear the stories of this terrible disease taking its toll. One update you might consider to the article that could serve as another helpful resource to readers is that, while it's true there is no cure for FeLV, there is a product called Lymphocyte T-Cell Immunomodulator (LTCI) that received USDA approval in 2006 as a treatment aid for this indication. At least there's now an option to check out!

Dianna Mendez on August 11, 2012:

My cat died of this virus a few years back. It was heart wrenching to watch him slowly pass away. He was so sweet and never indicated to us that he was in pain. Thanks for posting this and I hope it helps others.

Angela Michelle Schultz (author) from United States on August 09, 2012:

Love the cats name!

Denise Handlon from North Carolina on August 08, 2012:

Angela, I'm glad you posted this very informative hub. I just found out about this virus when I took our two kittens for a wellness checkup. I had not heard of this before because I've not had a housecat for a pet in many years. Our two kittens came to us by way of a mama stray who revealed to us her litter one day. We have no idea if there were other kittens, and I assume there were more than two, but we suspiciously look at the neighborhood toms and play the "who's your daddy" game.

In the meantime, our vet educated us and tested the little ones. TC Tiger (TomCat Tiger), and Raisin Le Pew (aka stinkbomb) came out with a clean bill of health and will be attending their second checkup in a couple of weeks for their follow up booster and neutering appointment. No babies allowed in my house-at least not the four pawed, furry version! LOL

Great hub; rated up and I/U BTW-love the avatar and it was the Peacock which caught my eye in the first place! Beautiful.

Angela Michelle Schultz (author) from United States on August 06, 2012:


I think this one is so heart wrenching because they can be healthy for so long with the disease, and then the slightest infection can kill them.

Angela Michelle Schultz (author) from United States on August 06, 2012:

Jackie, I had a cat that was affected by insulation as well. For whatever reason she loved the stuff, and would eat it. She actually is still living, but for awhile was very unhealthy. Fortunately, once we realized what the problem was, it fixed itself.

Angela Michelle Schultz (author) from United States on August 06, 2012:

Lucky Cats, I actually am not the person who set up Marley's fund, but when I saw it, I wanted to add it onto my site, to make others aware that a fund is out there.

Lela from Somewhere near the heart of Texas on August 06, 2012:

I've lost two great cats to FLV. They lived fairly normally until they were about 8 years old. Then they suddenly got sick and died quickly. It was not a nice disease. But then, there probably isn't a nice disease at all.

It hurts to lose a pet, no matter what the cause.

Jackie Lynnley from the beautiful south on August 06, 2012:

What a shame. My cat is seventeen and she has been through a lot but I think it was mostly from getting into insulation somewhere years back. Sort of an allergy thing but we seem to have it whipped for the most part. She is white, which I have read makes her weaker for some reason but she seems to be enjoying age and just soaking up the sun.

Interesting write, voted up.

David Hunt from Cedar Rapids, Iowa on August 06, 2012:

This is an awesome hub. Thank you for writing such a clear and easy-to-read article. Our cats are like family, so this is great information. Fortunately, ours are always indoors. Great pictures, too. The video... is heart-breaking and heart-warming. It gave me chills. Voted up, awesome, shared.

Kathy from The beautiful Napa Valley, California on August 05, 2012:

Hi Angela Michelle. Oh, you've touched my very core with this one. I am sorry about Marley. Believe me when I tell you that I know how it feels to realize that a dearly loved kitty companion has been disgnosed with FeLV. It is like your breath is suddenly taken away. This hub is very sensitive and so well written. It is so important to make sure that our cats no longer roam the streets and neighbors' yards because, it is a fact; infections, diseases and other disastrous possibilities are out there, endangering our cats' lives. Over the last decade; we;ve lost Little Girl, Tucker, Yellow Guy, Barney, BobCat, Scamp, and, most recently, Handsome to complications as a result of FeLV. They were all rescued cats in SE Kansas..abandoned, left to fend for themselves. We gave them wonderfully loved lives but, in the end; it's very difficult to beat this disease. It is so invasive. Your video is touching. It is wonderful that you've set up Marley's Fund to help other cats . you have my deepest sympathy and undestanding and gratitude for placing this very helpful information on Hub Pages. Kathy

There's a vaccine available to prevent infection from the virus. Since leukemia in cats is always caused by the virus, preventing infection will prevent the development of the disease. There's no effective treatment for the FeLV virus. Although vets can help provide palliative care to help improve life quality, there's no cure for it. Also keep in mind that cats can carry the virus for years without showing any symptoms and can still pass on the virus to other cats during that time.

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Tammy Dray has been writing since 1996. She specializes in health, wellness and travel topics and has credits in various publications including Woman's Day, Marie Claire, Adirondack Life and Self. She is also a seasoned independent traveler and a certified personal trainer and nutrition consultant. Dray is pursuing a criminal justice degree at Penn Foster College.

Feline leukemia virus (FeLV) is an agent that spreads easily between cats and has potentially lethal effects, causing a variety of secondary diseases that range from secondary infections to cancer.

Dr. Stanley Rubin, an internal medicine specialist at the University of Illinois Veterinary Teaching Hospital, cuddles his own cat.

Owner Awareness Has Reduced Prevalence of FeLV

“The overall prevalence of FeLV has decreased as cat owners’ awareness of the infection has increased and steps have been taken to control the disease, such as removing cats that are FeLV positive and restricting cats to indoor lifestyles,” Dr. Rubin says. Careful monitoring and the routine use of FeLV vaccines may also be helpful.

FeLV is transmitted between cats by prolonged close contact with saliva and nasal secretions, or by sharing common water or food sources. Sometimes it can be transmitted through bites or from moms to kittens via milk, or before the kittens are born.

The virus does not survive long outside a cat’s body, however. Dr. Rubin says there is no risk of cats transmitting FeLV to humans. “Numerous facts suggest that human infection is not possible,” Dr. Rubin assures.

How FeLV Causes Disease

Initially, the virus enters a cat’s bloodstream and starts to multiply. Sometimes the cat’s immune system is strong enough to fight off the infection at this stage. If not, the virus eventually travels to the bone marrow, which is where some of the body’s immune cells are produced. At this point, cats have a harder time fighting off the virus and may have FeLV for the rest of their lives.

The infection can cause anemia (low number of red blood cells) and immunosuppression. “Having a weakened immune system leaves the cat susceptible to secondary infections, also called opportunistic infections,” says Dr. Rubin. “They are more readily affected by bacteria, viruses, fungi, and parasites.”

As the disease progresses, it may lead to neurologic disorders, kidney failure, arthritis, and abortion in pregnant cats.

Because FeLV hijacks the cells’ replicating machinery, it is not surprising that this disease can ultimately lead to tumor growth. In fact, FeLV is the most common cause of cancer in cats, with the most common type of cancer being lymphoma.

“A cat infected with FeLV may begin showing signs of lethargy, fever, weight loss, loss of appetite, and depression,” Dr. Rubin says.

Treatment and Prevention of FeLV

Since these signs could indicate a variety of diseases, veterinarians diagnose FeLV by collecting blood and performing tests to detect the presence of the virus in the cat.

Depending on the clinical signs, the patient may be treated with blood transfusions, medications for opportunistic infections, immunotherapy, chemotherapy, or antiviral medications.

“Vaccinations are available,” Dr. Rubin says, “but it is important to remember that they do not provide 100 percent protection against infection.”

Vaccines are important in certain geographic locations where FeLV is more prevalent, such as areas that have a high density of roaming cats. Owners should consult their veterinarian to determine if a vaccine is necessary in their location.

Preventive measures should also be taken to reduce the risk. FeLV can be prevented by keeping cats indoors to avoid contact with outdoor cats.

Survival times depend on how the infection progresses and manifests itself, the strength of the cat’s immune system, and the type (or strain) of FeLV. Some cats are able to completely overcome the infection while others may suffer from recurrent bouts of infection only when their immune systems are suppressed, such as when they are weakened by another sickness. Still others suffer from a persisting, also called progressive, form of the virus for the rest of their lives.

Cats with progressive infections in multi-cat households can live up to 3 years with FeLV. However, survival rates increase when affected cats are kept indoors in single-cat households with good veterinary care.

To learn more about feline leukemia virus, consult your local veterinarian.

Suggested Articles

Feline leukemia virus (FeLV) is one of the most common infectious diseases in cats, affecting between 2 and 3% of all cats in the United States. Infection rates are significantly higher (up to 30%) in cats that are ill or otherwise at high risk (see below). Fortunately, the prevalence of FeLV in cats has decreased significantly in the past 25 years since the development of an effective vaccine and accurate testing procedures.

Cats persistently infected with FeLV serve as sources of infection for other cats. The virus is shed in saliva, nasal secretions, urine, feces, and milk of infected cats. Cat-to-cat transfer of the virus may occur from a bite wound, during mutual grooming, and (rarely) through the shared use of litter boxes and feeding dishes. Transmission can also take place from an infected mother cat to her kittens, either before they are born or while they are nursing. FeLV does not survive long outside a cat's body – probably less than a few hours under normal household conditions.

Cats at greatest risk of FeLV infection are those that may be exposed to infected cats, either via prolonged close contact or through bite wounds. Such cats include cats living with infected cats or with cats of unknown infection status, cats allowed outdoors unsupervised where they may be bitten by an infected cat, and kittens born to infected mothers.

Kittens are much more susceptible to FeLV infection than are adult cats, and therefore are at the greatest risk of infection if exposed. However, even healthy adult cats can become infected if sufficiently exposed.

Clinical Signs
FeLV adversely affects a cat's body in many ways. It is the most common cause of cancer in cats, may cause various blood disorders, and may lead to a state of immune deficiency that hinders a cat's ability to protect itself against other infections. Because of this, common bacteria, viruses, protozoa, and fungi that usually do not affect healthy cats can cause severe illness in FeLV-infected cats. These secondary infections are responsible for many of the diseases associated with FeLV.

During the early stages of infection, it is common for cats to exhibit no signs of disease at all. Over time, however, (weeks, months, or even years) an infected cat's health may progressively deteriorate or he/she may experience repeating cycles of illness and relative health. Signs can include:

  • Loss of appetite
  • Progressive weight loss
  • Poor coat condition
  • Enlarged lymph nodes
  • Persistent fever
  • Pale gums and other mucus membranes
  • Inflammation of the gums (gingivitis) and mouth (stomatitis)
  • Infections of the skin, urinary bladder, and upper respiratory tract
  • Persistent diarrhea
  • Seizures, behavior changes, and other neurological disorders
  • A variety of eye conditions
  • Abortion of kittens or other reproductive failures

Two types of blood tests are commonly used to diagnose FeLV, both of which detect a protein component of the virus called FeLV P27. One of these tests, called an enzyme-linked immunosorbent assay (ELISA), is usually performed first as a screening tool, and can be run in a veterinarian's office. ELISA-type tests detect the presence of free FeLV particles that are commonly found in the bloodstream during both the early and late stages of infection.

The indirect immunofluorescent antibody assay (IFA) test is usually sent out to a diagnostic laboratory after a positive ELISA test to confirm FeLV infection and determine whether the cat has reached the later stages of infection. IFA tests detect the presence of virus particles within white blood cells, usually an indication of a more advanced infection. The majority of cats that test positive by IFA remain infected for life. In some cases, isolating the whole virus or detecting DNA of the virus using a test called a polymerase chain reaction (PCR) may be recommended to determine whether FeLV has infected the bone marrow. Always consult with your veterinarian to determine which tests are appropriate for your cat.

Treatment and Prevention
Although there are some therapies that have been shown to decrease the amount of FeLV in the bloodstream of affected cats, these therapies may have significant side effects and may not be effective in all cases. Unfortunately, there is currently no definitive cure for FeLV. Veterinarians treating and managing FeLV-positive cats showing signs of disease usually treat specific problems (like prescribing antibiotics for bacterial infections, or performing blood transfusions for severe anemia).

The only sure way to protect cats from FeLV is to prevent their exposure to FeLV-infected cats. Keeping cats indoors, away from potentially infected cats is recommended. If outdoor access is allowed, provide supervision or place cats in a secure enclosure to prevent wandering and fighting. All cats should be tested for FeLV prior to introducing them into a home, and infection-free cats should be housed separately from infected cats. Food and water bowls and litter boxes should not be shared between FeLV-infected cats and non-infected cats. Unfortunately, many FeLV-infected cats are not diagnosed until after they have lived with other cats. In such cases, all other cats in the household should be tested for FeLV. Ideally, infected and non-infected cats should then be separated to eliminate the potential for FeLV transmission.

A relatively effective vaccine against FeLV is available, although it will not protect 100% of cats vaccinated, and it is not considered a core vaccine. Owners contemplating FeLV vaccination for their uninfected cats should consider the cats' risk of exposure to FeLV-infected cats and discuss the advantages and disadvantages of vaccination with a veterinarian. Since not all vaccinated cats will be protected by vaccination, preventing exposure remains important even for vaccinated pets. FeLV vaccines will not cause false positive FeLV results on ELISA, IFA, or any other available FeLV tests.

Although a diagnosis of FeLV can be emotionally devastating, it is important to realize that cats with FeLV can live normal lives for prolonged periods of time. The median survival time for cats after FeLV is diagnosed is 2.5 years. Once a cat has been diagnosed with FeLV, careful monitoring of weight, appetite, activity level, elimination habits, appearance of the mouth and eyes, and behavior is an important part of managing this disease. Any signs of abnormality in any of these areas should prompt immediate consultation with a veterinarian.

Signs of Feline Leukemia

FeLV passes through two stages-primary and secondary viremia-after a cat has been exposed to the virus. Most cats can fight off the primary phase of the disease, but by the time the secondary stage takes hold, the cat's immune system is weakened, which leaves your cat prone to secondary infections.

Clinical signs of FeLV infection can include anemia, appetite and weight loss, eye problems, fever, gum and mouth inflammation, neurological problems, pale oral tissues, persistent diarrhea, poor coat quality, reproductive problems, seizures, skin infections, swollen lymph nodes and weakness.

Watch the video: How To Protect Your Cat From Feline Leukemia Virus. Pet Health (July 2021).