By Dial A Vet Veterinary Team
Feline leukaemia virus (FeLV) is one of the most important infectious diseases of cats. It spreads between cats through close contact, weakens the immune system, and can lead to anaemia and cancer. A positive test result is not always the end of the story, though. Some cats fight off the infection, and many cats with persistent infection live for several good years with careful care. This page explains how FeLV spreads, what the test results mean, and how to protect your cat. For the related but different virus FIV, see feline immunodeficiency virus.
Key takeaways
- FeLV spreads mainly through saliva, during mutual grooming, sharing bowls, and bites. Kittens can be infected by their mother.
- Outcomes vary. Some cats clear the virus, some keep it hidden in their bone marrow, and some become persistently infected.
- Persistently infected cats are at higher risk of anaemia, infections, and lymphoma.
- Testing is recommended for all new cats and kittens and for sick cats, with follow-up testing to confirm results.
- Vaccination is available and is recommended for cats at risk, such as cats that go outdoors or live with an infected cat.
How FeLV spreads
The virus is shed in large amounts in saliva, and also in nasal secretions, urine, faeces, and milk. Friendly cats that groom each other and share food and water bowls are at risk, as are cats that fight. Kittens can be infected before birth or through nursing. FeLV does not survive long in the environment, and it does not infect people or dogs.
What happens after infection
After exposure, a cat's immune response determines the outcome:
- Abortive infection: the immune system clears the virus quickly.
- Regressive infection: the virus is controlled but remains hidden in the body. These cats usually do not shed the virus and often stay healthy, although it can reactivate during illness or stress.
- Progressive infection: the virus is not controlled. These cats shed virus and are more likely to develop FeLV-related disease, often within a few years.
Signs of FeLV-related disease
- Weight loss and poor appetite
- Pale gums from anaemia
- Recurrent infections of the skin, mouth, eyes, or respiratory tract
- Inflamed gums and mouth
- Enlarged lymph nodes
- Persistent fever
- Diarrhoea
- Lethargy and hiding
- Breathing difficulty, which can happen with lymphoma in the chest
Many infected cats show no signs at all early on, which is why testing matters.
When it is urgent
Go to an emergency veterinary hospital straight away if your cat:
- Is breathing with an open mouth or with obvious effort (see breathing problems in cats)
- Has very pale or white gums, or is weak and collapsing
- Has not eaten for more than a day
- Is hiding and unresponsive
- Has a high fever or seems very unwell
Testing and diagnosis
Most clinics use an in-house blood test that detects a viral protein (antigen). A positive result in a healthy cat should usually be confirmed, often with a different test type such as PCR, and retesting after several weeks helps distinguish a transient infection from a progressive one. Kittens can test positive or negative early on, so the 2020 AAFP retrovirus guidelines recommend retesting in some situations. Testing is advised for every new cat or kitten before it joins a household, for sick cats, and before vaccination. Your vet will interpret results with your cat's history.
Management, in overview
There is no cure for FeLV. Care focuses on keeping infected cats healthy for as long as possible:
- Check-ups every six months, with blood tests to catch anaemia or other changes early
- Prompt treatment of infections and other illnesses
- A complete, balanced diet, avoiding raw food, which carries infection risks
- Keeping the cat indoors to protect it from infections and to avoid spreading FeLV to other cats
- Specific treatments, such as chemotherapy for lymphoma or supportive care for anaemia, when needed
Your vet will tailor treatment to your cat's situation and talk through options as needs change.
Prevention
- Test new cats before introducing them to your household.
- Vaccinate cats at risk. WSAVA guidelines consider FeLV vaccination for all kittens, with ongoing vaccination based on lifestyle. Your vet will advise what suits your cat.
- Keep cats indoors or in an enclosure to reduce fights and contact with unknown cats.
- Desex cats to reduce roaming and fighting.
- If one cat in a household is positive, ask your vet about testing and vaccinating the others and reducing shared bowls.
FAQ
How long do cats with FeLV live?
Cats with progressive infection often live a few years after diagnosis, and some live much longer with good care. Cats with regressive infection may have a normal lifespan.
Can my FeLV-positive cat live with other cats?
It is possible with precautions, but there is a risk of spread. Discuss testing, vaccination, and separate bowls with your vet.
Can people catch feline leukaemia?
No. FeLV only infects cats.
Talk with a vet
If your cat has tested positive, or you want to talk through testing and vaccination, our vets can help by video. Book a consult at dialavet.com. If your cat is struggling to breathe, is collapsing, or is very unwell, go to an emergency vet hospital now.
References
- Little S, et al. 2020 AAFP Feline Retrovirus Testing and Management Guidelines. Journal of Feline Medicine and Surgery.
- Cornell Feline Health Center. Feline Leukemia Virus.
- WSAVA Vaccination Guidelines Group. Guidelines for the vaccination of dogs and cats.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If your cat is seriously unwell, contact a veterinary hospital promptly.