What Is FeLV in Cats? Feline Leukemia Virus Explained
FeLV stands for feline leukemia virus — a common, important infectious disease of cats. This guide summarizes what veterinary sources say about the virus, infection outcomes, testing, and prevention — not a substitute for a veterinary exam.
Quick answer
What is FeLV in cats? FeLV is feline leukemia virus, a retrovirus and one of the most common and important infectious diseases of cats. According to the Cornell Feline Health Center, it affects roughly 2–3% of cats in the United States and Canada, with higher rates in ill or high-risk cats.
FeLV can suppress immunity, contribute to cancers and anemia, and lead to different infection outcomes (abortive, regressive, or progressive). There is no definitive cure; management focuses on secondary problems. See how FeLV is transmitted, FeLV symptoms, and treatment and life expectancy.
What Does FeLV Stand For?
FeLV stands for feline leukemia virus. Despite the name, FeLV is not only about “leukemia.” It is a virus that can cause a range of illnesses related to immune suppression, bone-marrow disease, cancers, and secondary infections.
Cornell notes that FeLV prevalence has declined over recent decades with better testing and vaccination, but it remains a clinically important infection — especially in high-risk groups.
What Does FeLV Do to Cats?
FeLV is a retrovirus: it inserts genetic material into infected cells. After exposure, cats may develop different infection patterns rather than one single “always fatal” course.
Veterinary evidence (Cornell): Infection outcomes include abortive (virus eliminated), regressive (virus controlled; cats may remain clinically well for long periods), and progressive (persistent infection with ongoing viral shedding and higher disease risk).
Progressive infection is associated with problems such as anemia, malignancies, and immunosuppression. Exact clinical problems vary by cat. The Merck Veterinary Manual likewise emphasizes that management depends on infection type and clinical signs.
How Do Cats Get FeLV? (Brief)
Infected cats shed FeLV in saliva (especially important), and also in feces, urine, and milk. Transmission typically requires close cat-to-cat contact.
Common routes include bite wounds, mutual grooming, shared food/water dishes and litter boxes, and mother-to-kitten transmission before birth or while nursing. The virus does not survive long outside a cat — Cornell estimates probably less than a few hours under normal household conditions.
Full detail: How Is FeLV Transmitted in Cats?.
What Are FeLV Symptoms? (Brief)
Early infection often has no obvious signs. Later, Cornell lists possible findings such as loss of appetite, weight loss, poor coat, enlarged lymph nodes, persistent fever, pale gums, gingivitis/stomatitis, secondary infections, diarrhea, neurologic signs, eye conditions, and reproductive failures.
These signs overlap many other diseases — they are reasons to see a veterinarian, not a self-diagnosis. Full guide: FeLV Symptoms in Cats.
Is FeLV Contagious to Other Cats?
Yes — FeLV is contagious among cats through close contact and body fluids, especially saliva. It is a feline virus; veterinary sources describe it as species-specific with no evidence it infects humans.
Indoor living reduces outdoor exposure risk but does not eliminate household or adoption-related exposure if an infected cat shares space, bowls, or litter boxes. See transmission and FeLV vs FIV for how FeLV’s spread differs from FIV.
How Is FeLV Diagnosed?
Veterinarians commonly use ELISA screening for viral antigen, with IFA and PCR among confirmatory or clarifying tools. Cornell stresses that one test at one timepoint is not enough to determine progressive infection status.
After recent exposure, retesting is often recommended about 3–6 weeks later; distinguishing progressive vs regressive infection may involve rechecks around 6–12 weeks (and sometimes additional testing). Always follow your veterinarian’s testing plan — do not interpret home “result charts” as a diagnosis.
Can FeLV Be Cured?
No definitive cure is described by Cornell or the Merck Veterinary Manual. Care focuses on managing secondary problems, monitoring, reducing stress and exposure to other infections, and supporting quality of life.
A vaccine is available and is considered a core vaccine for kittens by Cornell’s guidance; it is not 100% protective and does not cause false-positive ELISA/IFA results. Vaccination decisions belong with your veterinarian.
How Long Can Cats with FeLV Live? (Brief)
Outlook varies widely by infection type and clinical status. Cornell cites a median survival of about 2.5 years after diagnosis, with some cats living much longer, especially with regressive infection. Merck notes that many cats die within 3 years of diagnosis, while others remain subclinically affected for multiple years.
Details and care context: FeLV Treatment and Life Expectancy.
Kittens vs Adult Cats
Kittens are generally at higher risk of developing progressive infection after exposure, which is one reason FeLV vaccination is emphasized as a core kitten vaccine in Cornell’s materials. Adults can still become infected.
Age alone does not determine outcome. Exposure history, household contact, outdoor access, and concurrent illness all matter — discuss risk with a veterinarian when adopting or introducing cats.
Frequently asked questions
Can indoor cats get FeLV?+
Yes. Keeping cats indoors reduces contact with unknown outdoor cats, but household contact, boarding, shelters, and adopting an infected cat can still expose an indoor cat. Cornell notes indoor living helps but is not a guarantee against all exposure scenarios.
Does FeLV vaccine cause a false-positive FeLV test?+
According to Cornell, FeLV vaccines will not cause false-positive results on ELISA, IFA, or other available FeLV tests. Testing questions should still be reviewed with your veterinarian.
Is FeLV the same as FIV?+
No. Both are feline retroviruses that can affect immunity, but they differ in genetics, typical transmission routes, and some management details. See our FeLV vs FIV comparison guide.
Should I euthanize a cat just because of a positive FeLV test?+
A positive test alone is not an automatic reason for euthanasia. Outcomes vary (abortive, regressive, progressive), and many cats need confirmatory and follow-up testing plus individualized veterinary care. Decisions must be made with a licensed veterinarian.
Related FeLV & feline leukemia guides
FeLV Symptoms in Cats
Early and later signs, asymptomatic stages, and when to see a vet.
Read guideHow Is FeLV Transmitted?
Bite wounds, grooming, shared dishes, mother-to-kitten, and household survival.
Read guideFeLV Treatment & Life Expectancy
No cure, supportive management, median survival figures, and long-term care.
Read guideFeLV vs FIV in Cats
How the two feline retroviruses differ in spread, testing, and outlook.
Read guideSources
Educational summary drawn from veterinary reference pages. Always verify details with a licensed veterinarian and the original sources:
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