Feline Leukemia in Cats
Feline leukemia virus (FeLV) can weaken the immune system, cause anemia, and increase cancer risk in cats. Because cats often hide illness until they are quite sick, early testing and veterinary follow-up are especially important.
Prompt veterinary care matters
Feline leukemia virus is not always an immediate emergency, but it is a serious, progressive viral disease that can become life-threatening. Schedule a veterinary visit promptly if your cat has weight loss, pale gums, fever, mouth inflammation, poor appetite, repeated infections, or unusual tiredness. Seek emergency care right away for trouble breathing, collapse, severe weakness, or uncontrolled bleeding.
Symptoms to Watch For
Low energy
Lethargy, hiding more than usual, or less interest in play.
Poor appetite
Eating less, weight loss, or gradual muscle loss.
Pale gums
Can be a sign of anemia, which is common in FeLV-related illness.
Mouth problems
Inflamed gums, stomatitis, bad breath, or pain when eating.
Recurring illness
Repeated infections, fever, diarrhea, or slow recovery from routine illness.
Other body-wide signs
Enlarged lymph nodes, reproductive problems, eye changes, or neurologic signs in some cats.
What Causes Feline Leukemia
Feline leukemia is caused by feline leukemia virus (FeLV), a contagious retrovirus that infects only cats. It spreads mainly through prolonged close contact with infected saliva and other body fluids, including mutual grooming, shared bowls or litter boxes, and bite wounds. Mother cats can also pass the virus to kittens before birth or through milk. Not every exposed cat becomes permanently infected, but kittens are especially vulnerable, and infected cats may later develop immune suppression, anemia, lymphoma or leukemia, and other chronic health problems. There is no known breed predisposition consistently identified as a major risk factor; exposure risk and age matter more than breed.
- Young kittens are at the highest risk of infection after exposure.
- Outdoor access increases exposure to infected cats.
- Living with FeLV-positive cats or cats of unknown status raises risk.
- Unneutered males may be at higher risk because fighting and bite wounds can spread the virus.
- Multi-cat households, shelters, and homes that bring in new cats without testing have higher transmission risk.
How It's Diagnosed
Diagnosis usually starts with a quick in-clinic blood test that detects FeLV antigen. If the result is positive, your veterinarian may recommend confirmatory testing or repeat testing, because a cat's infection status can change over time and some cats may clear infection while others become persistently infected. Your vet may also run a complete blood count, chemistry panel, urinalysis, and additional tests to look for anemia, secondary infections, or FeLV-related complications such as lymphoma. If your cat is sick, your veterinarian may suggest imaging, lymph node evaluation, or tissue sampling depending on the signs present.
- Initial screening often uses a rapid blood ELISA test.
- Positive results may be confirmed with additional laboratory testing or follow-up testing.
- Bloodwork helps check for anemia, low white blood cell counts, and organ involvement.
- Cats should be tested before entering a household with other cats and before FeLV vaccination.
Treatment Options
There is no cure that eliminates FeLV from the body, so treatment focuses on supportive care, monitoring, and managing complications early. Some FeLV-positive cats remain stable for years with regular veterinary checkups, good nutrition, stress reduction, parasite prevention, and fast treatment of secondary infections. Your veterinarian may recommend therapies for anemia, infections, dental or mouth disease, cancer, pain, or other FeLV-related problems based on your cat's specific condition. Keeping infected cats indoors helps protect them from additional infections and prevents spread to other cats.
- Regular veterinary rechecks are important, often at least every 6 months.
- Treat secondary infections promptly because immune suppression can make them more serious.
- Keep FeLV-positive cats indoors and separate from uninfected cats when possible.
- Discuss vaccination and testing plans for other cats in the household with your veterinarian.
- Spaying or neutering is recommended for infected cats unless your veterinarian advises otherwise.
Living with Feline Leukemia
Common Questions About Feline Leukemia in Cats
Is feline leukemia contagious to other cats?
Can indoor cats get feline leukemia?
Is there a cure for feline leukemia?
How long can a cat live with feline leukemia?
Should cats be vaccinated against FeLV?
When should I call a vet?
Sources
- Cornell Feline Health Center — Feline Leukemia Virus
- Merck Veterinary Manual — Feline Leukemia Virus (FeLV)
- VCA Animal Hospitals — Feline Leukemia Virus Disease Complex
- American Association of Feline Practitioners — Feline Retrovirus Management
- Feline Leukemia Virus (FeLV): Symptoms, Testing & Treatment — SpectrumCare
Disclaimer: The information provided in this article is for educational purposes only and does not constitute veterinary medical advice. Reading this content does not establish a veterinarian-client-patient relationship. Every pet is different — always consult a licensed veterinarian before making decisions about your pet's health, diet, or care. If you'd like personalized guidance, you can talk to one of our vets. If your pet is experiencing a medical emergency, contact your local emergency animal hospital immediately.