Feline Leukemia (FeLV): Signs, Testing & Care
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Feline leukemia virus (FeLV) is a contagious virus that weakens a cat's immune system and can cause anemia, infections and cancers. It spreads mainly through close, friendly contact between cats — shared bowls, grooming, and bites. A positive test isn't an immediate death sentence: many FeLV-positive cats live comfortably for years with attentive, indoor care, and a vaccine plus keeping cats indoors greatly lowers the risk.
What FeLV is and how it spreads
FeLV is a retrovirus that infects the immune and blood-forming systems. Over time it can suppress the immune response, cause persistent anemia, and raise the risk of certain cancers like lymphoma. Some cats mount an effective response and clear or contain the virus; others become persistently infected.
It spreads through prolonged, friendly contact — mutual grooming, sharing food and water bowls and litter boxes, and bite wounds. A queen can also pass it to her kittens. Kittens and young cats are far more susceptible than healthy adults, whose immune systems more often fend it off. It does not infect humans, dogs, or other non-feline pets.
Signs of FeLV infection
Early on, an infected cat may look completely healthy. As the virus affects the immune system, signs are broad and reflect secondary problems:
- Pale gums and weakness from anemia
- Recurrent or stubborn infections — skin, respiratory, mouth, bladder
- Persistent fever, poor appetite and weight loss
- Enlarged lymph nodes and a poor coat
- Pale or inflamed gums, and dental/mouth disease
- Lethargy and, over time, a general failure to thrive
Because these overlap with many other illnesses, any cat that keeps getting sick should be tested.
Testing and diagnosis
FeLV is diagnosed with blood tests, and it's common to test for FIV at the same time:
| Test | What it shows |
|---|---|
| ELISA (in-clinic) | Detects virus antigen in blood; a good first-line screen, often run chairside. |
| IFA or PCR (lab) | Confirms persistent infection and helps clarify a positive or unexpected screen. |
| CBC | Looks for anemia and low white-cell counts linked to the disease. |
Because a cat's status can evolve after exposure, your vet may recommend retesting after a period to confirm whether infection has become persistent. New kittens and cats should be tested before joining a household.
Caring for a FeLV-positive cat
There's no cure that clears the virus, but the goal — a good quality of life for as long as possible — is realistic with the right care:
- Keep the cat strictly indoors, both to protect it from infections and to prevent spreading FeLV to other cats.
- Feed a complete, balanced diet and avoid raw food, which carries extra infection risk for an immune-compromised cat.
- See your vet twice a year for a full checkup, weight check and bloodwork, so problems are caught early.
- Treat infections promptly and aggressively, since a weakened immune system struggles to keep up.
- Keep parasite prevention and dental care current.
Practical take: A FeLV-positive diagnosis is a reason for closer monitoring, not despair. Many of these cats enjoy years of good life with a watchful owner and vet.
Prevention and why tracking helps
The best protection is keeping cats indoors and testing new cats before introducing them. An FeLV vaccine is available and recommended especially for cats with any outdoor access or exposure to other cats — your vet will advise based on lifestyle. Testing before vaccination is standard.
For a positive cat, small changes are the early warning system: a dropping weight, gums looking paler, appetite tapering off, or infections that keep recurring. Logging weight, appetite and any illnesses over time turns those subtle shifts into a trend you and your vet can act on before a small problem becomes a big one.
Watch an FeLV cat's health closely over time
Tavi keeps your cat's weight, appetite, symptoms and vet-visit results in one place and charts them over time — so with a condition like FeLV you catch a downturn early and walk into each checkup with a real history. Free for your first pet.
Frequently asked questions
How long can a cat live with feline leukemia?
It varies widely. Some FeLV-positive cats live many years with good indoor care and regular vet monitoring, while others decline sooner from secondary illnesses. Twice-yearly checkups and prompt treatment of infections make a real difference to both length and quality of life.
Can feline leukemia spread to humans or dogs?
No. FeLV only infects cats and cannot be transmitted to people, dogs, or other non-feline pets. It spreads between cats through prolonged friendly contact, shared bowls, and bite wounds, so the risk is to other cats in the home.
Can a FeLV-positive cat live with other cats?
It's risky, because FeLV spreads through grooming, shared bowls and bites. The safest approach is a single-cat household, or keeping the positive cat separated. If other cats live in the home, they should be tested, vaccinated where appropriate, and their risk discussed with your vet.
Is there a vaccine for feline leukemia?
Yes. The FeLV vaccine is recommended especially for cats with outdoor access or contact with other cats, and it's a standard part of the kitten series in many practices. Cats are tested before vaccination. The vaccine reduces risk but doesn't replace keeping cats indoors.
What is the difference between FeLV and FIV?
Both are feline retroviruses that affect the immune system, but they differ. FeLV spreads mainly through friendly contact like grooming and shared bowls and tends to have a more serious outlook, while FIV spreads chiefly through bite wounds and many FIV cats live long, near-normal lives. Cats are often tested for both together.
Tavi's guides are informational and not a substitute for professional veterinary advice, diagnosis or treatment. When in doubt, call your veterinarian. Sources: Cornell University Feline Health Center; American Association of Feline Practitioners (AAFP); VCA Animal Hospitals; Merck Veterinary Manual