Ask a Veterinarian: Feline Leukemia Virus (FeLV)
|What is Feline Leukemia Virus?
Feline leukemia virus (normally abbreviated “FeLV”) is a contagious organism that is one of the most common infections of cats around the world. It is part of a family of viruses called “retroviruses” that are able to invade a cat’s body, becoming integrated into the cat’s own DNA. Because of this ability to invade, FeLV is termed an “oncogene.” Oncogenes are genes in the body that can undergo a transformation into cancer cells.
Although it is one of the most common infections in cats, it only affects approximately 2% of all cats in the U.S. and this percentage continues to drop because of the effectiveness of preventative vaccination protocols.
Unlike other viruses that can make us temporarily sick–think of the “flu,” FeLV can cause a number of different problems when our cat becomes infected.
How can my cat catch this virus?
There are two main ways a cat can catch FeLV. A pregnant infected mother cat can infect her kittens before they are born (transplacental) or after birth via nursing (virus is shed into the milk). The second way a cat catches FeLV is through very close contact with an infected cat. The virus is shed in blood (exchanged when cats fight), urine, feces, and nasal secretions. Young cats under 2 years old are far more susceptible to catching FeLV. And don’t think because your cat is an indoor cat that they are safe from the virus. Basically young, indoor/outdoor or outdoor cats that might run into a feral or FeLV carrying cat are most likely to catch the virus.
Mature cats and especially cats that have been given the preventative FeLV vaccine are often completely immune to the virus.
What kind of symptoms can FeLV cause?
When a young cat first catches FeLV they might become very sick with a fever, have a poor appetite, lethargy, weight loss, enlarged lymph nodes, and dehydration. In other situations, the initial illness after exposure to FeLV is not that dramatic. Instead what happens is the virus lays latent and later, differing illnesses develop. Common secondary infections because of a suppressed immune system include dental infections, tongue/mouth infections, eye troubles, upper respiratory tract infections, and abscesses. Symptoms associated with these infections include fever, drooling, loss of appetite, weight loss, unkempt appearance, ocular discharge, nasal discharge, sneezing, and general malaise.
Secondary cancers that develop because of latent FeLV include leukemias (white blood cell cancer), lymphomas and fibrosarcomas. All of these cancers are treatable but unfortunately prognosis is most often worse when you have FeLV + cancer. Symptoms vary widely but in general include lethargy and often loss of appetite. Lymphoma of the intestinal system is common and symptoms most often include vomiting, diarrhea, loss of appetite and weight loss.
Prevention of FeLV – Vaccination
After discussing the specific pros and cons of vaccination to prevent FeLV in your cat, your veterinarian will be able to give you great specific advice. In almost all cases and especially in young cats, FeLV vaccination is recommended to provide protection. Indoor-only cats are much less likely to run into FeLV but they can still slip outdoors so often vaccination does make the most sense.
Treatment and Prognosis of FeLV
Although many newer treatments exist for our FeLV + cats, nearly 80% of infected cats will die within three years of being diagnosed. This statistic is startling and sad, but with aggressive treatments and advanced care from veterinary internal medicine and oncology specialists when your FeLV + cat becomes ill, there is definitely more hope than there once was. Newer chemotherapy treatments and treatments with drugs like azidothymidine (AZT), feline interferon, staphylococcal protein A (SPA) are used to combat the cancers and infections FeLV + cats are more susceptible to.
One of the main keys to extending the lifespan of your FeLV cat is to get veterinary care at the first sign of any illness. This can be tough with cats because they love to hide their troubles. Watch for subtle signs like sleeping in an odd location, not grooming as much as normal—the cat will suddenly have a “rougher” hair coat or more dander than normal, change in behavior patterns, and decreased interest in food or treats.
Being a pet owner I am aware of the fact that Feline Leukemia Virus is leading cause of death in cats. Moreover, It is the most common cause of cancer in cats, it may cause various blood disorders, and it may lead to a state of immune deficiency. So, it’s important for your cat to have regular veterinary check ups.
YES! This is very true. Once yearly if your cat is young and then twice yearly is ideal once your cat is 8 years old or so. Talk to your vet about the ideal timing for YOUR specific kitty as some 8 year old cats are still kitten-like and once a year is fine. The opposite can be true too . . . Develop that relationship with a veterinarian you can easily communicate with, trust, and get specific advice for your specific much loved pet! Denise.
I couldn’t agree more that regular vet checkups are an absolute must. 80% fatality is staggering and actually quite depressing. Hopefully more research can be done in this area so that we can expand the happiness and lifespans of our beloved friends. Thank you for this very informative article.
Thank-you Emily! Denise.
Thank you for sharing!
It is the most common cause of cancer in cats, it may cause various blood disorders, and it may lead to a state of immune deficiency. So, it’s important for your cat to have regular veterinary check up!
I am happy to read your article.
Thanks for share the article.
Thank you so much.
I had my cat euthanized a few days back and she had FeLV. She had FeLV for nine years (9 years after the diagnosis) and remained in perfect healthy condition until the last two months when she developed an infection of her mammary gland which turned out to be a tumor. When she was diagnosed with FeLV in 2008 I thought she would not live long and be sick most of the rest of the time before she died. This was not the case at all. In fact, the sickest she ever was when she was at vet and was diagnosed with FeLV (besides her last few days) in 2008. She suddenly became sick and weak and wouldn’t eat so I took her to the vet who tested her for FeLV and she tested positive. Vet gave me antibiotics and steroids to give her and she perked back up. For nine years she never was as sick as in 2008 until just two days before she died. For 9 years she was healthy and rarely ever sick (she had four colds). Please if your cat is diagnosed don’t immediately have it euthanized. My cat lived a healthy, happy, life for nine years.
Hi Richard,
Thank you for sharing your experience. We’re so sorry to hear about your loss but are glad your cat lived a long healthy life with FeLV.Great advice for cat owners looking for additional guidance.
Sending good thoughts your way!