What is FeLV?
Feline leukemia virus (FeLV) is a virus that can infect cats. It was first discovered in cats that had leukemia, which is a cancer of circulating blood cells. Nowadays, we know that this virus does cause leukemia—one of the few known infections that can lead a cat to develop cancer—but most cats with feline leukemia virus are asymptomatic (do not show signs of symptoms). This asymptomatic state usually lasts for weeks to years until cats begin to show vague symptoms due to anemia, a weakened immune system, and eventually leukemia.
How does it spread?
FeLV can be transmitted among cats in close, prolonged contact with each other through saliva, urine, and other bodily fluids including nasal and eye secretions. It is extremely uncommon for a one-time exposure to lead to infection; rather, repeated exposure such as sharing food/water dishes and using common litter areas contribute to the spread of this virus between cats.
FeLV can live outside a cat on things for a few hours such as litter boxes, and food and water bowls. Regular disinfectants can kill the FeLV virus on surfaces faily easily, such as one part bleach to 30 parts water.
How is it Diagnosed?
Feline Leukemia is usually diagnosed one of two ways. Feline leukemia should be checked for as part of a routine health screen, such as when adopting a new cat or evaluating a cat’s other health issues, so this is one way to tell. Another way is if
the cat actually starts to exhibit more than one of the symptoms commonly associated with FeLV.
Signs & Symptoms of FeLV
Many cats can go long periods of time being asymptomatic (showing no sign of infection). Infected cats that do show signs of illness (clinical signs, symptoms) may have:
- Weight loss
- Weakness
- Fever
- Dehydration
- Inflammation of the lining of the nasal passages (rhinitis) causing nasal congestion and discharge
- Diarrhea
- Red eyes (conjunctivitis)
- Sores in the mouth
- Enlarged lymph nodes, and/or abscesses under the skin
- Anemia (decreased number of red blood cells) in cats is also commonly caused by FeLV
This virus also infects white blood cells, so the immune system commonly is weakened. As a result, cats infected with FeLV are susceptible to infections with other organisms (secondary infections) such as bacteria, other viruses, protozoa, and fungi which in turn can lead to other symptoms, including respiratory and intestinal problems.
What is the ideal home for a cat with FeLV?

NHS Team Member Sarah’s FeLV positive cat snuggled up at home!
Cats with FeLV need love just as much as any other cat! Cats that are FeLV positive should be kept indoors to prevent spreading the virus to other cats in the area or neighborhood. Due to reduced immune function from FeLV, keeping the cat indoors will also help prevent them from getting diseases that another cat might carry.
FeLV positive cats in a household with other FeLV negative cats should be isolated, and have separate items such as bowls and litter boxes. This is why cats that are FeLV positive are usually adopted out to homes that have no other cats in the household, or to a home with other FeLV positive cats.
How do you treat FeLV?
Cats with FeLV should be seen by the veterinarian every six months to watch out for sign of any secondary infections. Secondary infections can be things previously mentioned such as anemia, certain cancers, and things like intesinal problems. Always talk to a veterinarian about FeLV positive cats getting routine vaccinations, especially if it is enevitable that they will be in contact with other cats. There is also a vaccine made to help prevent FeLV, but this should not be given to a cat that is already FeLV positive.
There are no medications that can completely eliminate FeLV. Treatment plan of FeLV depends on cat’s medical history, immune system, and other medical conditions. It is essential that FeLV positive cats get the proper nutrion that they need and that secondary conditions also be treated. Sometimes things like fluids for hydrations are necessary, so they may need to make a visit to the veterinarian.
Tips for Cats Living with FeLV:
- Keep all FeLV positive cats strictly indoors, do not let them roam outside.
- Understand that having FeLV does not mean a cat is suffering; some cats naturally keep the virus in check for years and have a normal quality of life and life expectancy.
- Realize that the seriousness of a cat’s FeLV infection is highly variable and that the most reliable information comes from the evaluation of your specific cat (rather than generalizations in brochures, textbook chapters or Internet sources).
- Establish a schedule of regular visits to your veterinarian if your cat has FeLV.
- Give medication(s) prescribed for your pet exactly as directed.
Call your Veterinarian if your FeLV positive cat:
- Has lost weight, decreased appetite, weakness, been bitten by another cat, diarrhea, sores in the mouth, or abscesses (lumps under the skin).
- Your cat is experiencing sluggishness, weakness, decreased appetite, hives (bumps under the skin), vomiting, diarrhea, or any abnormal behavior as general signs of worsening of the disease; a recheck visit to the veterinarian may be needed.
To learn more about your pet’s health, visit the Pet Health section of our blog.
This post was written in Collaboration with one of Nevada Humane Society’s dedicated Veterinarians.