Feline Leukaemia Virus (FeLV)
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Feline leukaemia virus, or FeLV, is a retrovirus that can suppress the immune system, affect bone marrow and increase the risk of lymphoma and other cancers. It is spread mainly through close contact with infected cats, particularly saliva during mutual grooming and shared close living, although transmission can also occur through bites and from an infected queen to kittens.
Not every exposure leads to the same outcome. Some cats control the infection before persistent viraemia develops, while others develop progressive infection with ongoing virus in the blood and a greater risk of disease.
FeLV-associated illness is variable. Cats may develop recurrent infections, anaemia, weight loss, poor coat condition, fever, oral disease, reproductive problems or cancer. A cat can also remain clinically well for a significant period despite confirmed infection.
FeLV is not a reason to assume immediate severe illness. Infected cats benefit from proactive veterinary care and protection from additional infectious exposure. The most effective prevention is knowing the FeLV status of cats before introductions, keeping infected cats indoors and vaccinating cats whose lifestyle creates meaningful exposure risk.
Infection status also affects household planning. A progressively infected cat can shed virus and expose susceptible companions, but this does not mean the cat must live without feline companionship in every circumstance. Decisions depend on the status of other cats, vaccination, behaviour and the household’s ability to prevent transmission.
Kittens and young cats are especially susceptible to progressive FeLV infection, while close social exposure permits saliva-borne transmission between household companions. Kittens and young cats are especially susceptible to progressive infection. For prevention, cats with outdoor access or contact with cats of unknown status should have risk assessed for FeLV vaccination. Vaccination reduces risk but is not considered completely protective against heavy exposure.
Screening & Early Detection
A point-of-care antigen test is commonly used first. A positive result should be interpreted with the cat’s risk, clinical status and previous tests. Repeat antigen testing, laboratory testing or PCR may be recommended to clarify whether infection is progressive, regressive or transiently detected. A negative test immediately after exposure can be too early, so retesting after an appropriate interval may be necessary.
All sick cats can reasonably be considered for FeLV testing when status is unknown because the virus can contribute to many different presentations. Blood counts are useful in infected cats because anaemia and other marrow abnormalities may develop.
Vaccination does not replace testing and separation from known infected cats. Routine screening is less frequent in low-risk indoor adults with documented negative status, but any new exposure changes that assessment.
Modern testing recognises that infection status can be more complex than a simple lifetime positive-or-negative label. Screening commonly begins with an antigen test that detects circulating viral protein. Positive results may need confirmation or repeat testing depending on the cat’s history and timing of exposure. PCR can provide additional information in selected cases. A recently exposed cat may test negative before infection becomes detectable, so timing matters.
Treatment & Management
There is no treatment that reliably eliminates FeLV from a progressively infected cat, so management focuses on preventing secondary disease and maintaining quality of life. Infected cats are kept indoors to reduce exposure to infections and to prevent transmission to other cats. Good nutrition, parasite control and prompt attention to even minor illness are important.
Veterinary examinations are usually scheduled more frequently than for uninfected cats. Body weight, oral health, lymph nodes and general condition are monitored, with blood counts and other tests used according to clinical status. Secondary bacterial infections are treated appropriately rather than assuming every problem is directly caused by FeLV.
FeLV-associated lymphoma, anaemia or other complications are treated according to the specific diagnosis. Chemotherapy can produce remission in some cats with lymphoma, although prognosis depends on tumour type and overall health. Blood transfusion or other supportive care may be needed for severe anaemia.
FeLV-positive and FeLV-negative cats are ideally housed separately. A positive cat can still have months or years of good-quality life, so decisions should be based on current health rather than the test result alone.
Breeds or species affected
Abyssinian
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American Bobtail
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American Curl
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American Shorthair
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American Wirehair
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Arabian Mau
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Aegean
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Australian Mist
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Balinese
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Bengal
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Birman
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Bombay
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British Longhair
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British Shorthair
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Burmese
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Burmilla
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Chartreux
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Chausie
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Colorpoint Shorthair
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Cornish Rex
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Cymric
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Devon Rex
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Domestic Longhair
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Domestic Medium Hair
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Domestic Shorthair
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Donskoy
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Egyptian Mau
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European Shorthair
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Exotic Shorthair
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Havana Brown
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Highlander
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Himalayan
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Japanese Bobtail
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Khao Manee
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Korat
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Kurilian Bobtail
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LaPerm
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Lykoi
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Maine Coon
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Manx
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Minuet
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Minskin
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Munchkin
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Nebelung
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Norwegian Forest Cat
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Ocicat
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Oriental Longhair
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Oriental Shorthair
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Persian
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Peterbald
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Pixiebob
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RagaMuffin
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Ragdoll
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Russian Blue
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Savannah
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Scottish Fold
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Scottish Straight
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Selkirk Rex
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Siamese
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Siberian
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Singapura
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Snowshoe
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Somali
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Sphynx
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Thai
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Tonkinese
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Toybob
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Toyger
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Turkish Angora
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Turkish Van
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Bambino
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Cheetoh
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Dwelf
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Elf Cat
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Genetta
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Kinkalow
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Lambkin
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Serengeti
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Skookum
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Ukrainian Levkoy
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