What is Feline Leukemia Virus (FeLV)?

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Feline Leukemia Virus (FeLV) is a common infectious disease that occurs in cats. It can cause many types of illness as well as death in infected cats. However, FeLV does not infect humans or other animals.

Feline leukemia virus infection is more commonly spread among cats that live together. The virus can also be spread from mother to kittens, and among cats that fight. It is mainly spread through saliva when cats groom each other, and when food and water bowls are shared.

In North America, about 4% of tested cats are found to be infected with FeLV. In Latin America, up to 42% of tested cats are found to be infected.

How is FeLV Transmitted?

Transmission occurs through saliva, feces, milk, and urine of an infected cat. However, the most common transmission route is through saliva.

  • FeLV is also transferred through grooming, licking, biting, shared dishes, and shared litter pans.
  • FeLV can also be transmitted through a blood transfusion.
  • An infected mother can transfer FeLV to her kittens during pregnancy or nursing.
  • Close cat-to-cat contact is required to transmit the disease.
  • Young cats, especially those under 4-6 months of age, are the most susceptible to FeLV since their immune systems are not fully mature.
  • FeLV cannot be transmitted to people, dogs, or other animals.

Signs and Symptoms of FeLV

When first exposed to FeLV, a cat might not show any signs of illness. Some cats that are exposed to FeLV can clear the virus completely from their body. Other cats are able to control the infection, preventing illness. In some cats, the infection will become active in their body and they will develop problems such as low red blood cells (anemia) or cancer. These problems can be severe and even fatal.


The signs and symptoms of FeLV vary greatly depending on the infected cells. Signs may include:

  • Fever
  • Loss of appetite
  • Weight loss
  • Lethargy
  • Poor coat or fur condition
  • Enlarged lymph nodes
  • Pale gums
  • Infections of the skin, bladder, and upper respiratory
  • Reproductive problems in unspayed females


Eventually, FeLV-associated diseases occur and can include:

  • Anemia
  • Liver disease
  • Intestinal disease and reproductive problems
  • Lymphoma or leukemia
  • Chronic respiratory infections
  • Chronic gingivitis and stomatitis (inflammation of the gums and mouth)
  • Poor healing of wounds and abscesses


Your cat can be tested for FeLV infection. There are many times in your cat’s life when your veterinarian will recommend testing for FeLV and common infections, including:

  • Any time your cat is sick.
  • If your cat goes outdoors.
  • If your cat fights with other cats.


If your cat is new to the family or you adopt another cat, testing is advised before introducing the new cat to other cats in the household.

If your cat tests positive for FeLV, further tests may be recommended by your veterinarian. Even if your cat’s first test result is negative, your veterinarian may still advise repeat testing in the future.


There are several vaccines available to protect cats from FeLV infection. Vaccination is recommended for all kittens, again one year later, and regularly for cats that have access outdoors.

Adult indoor-only cats living alone or with uninfected cats may not need to be vaccinated after the first 2 years. Your veterinarian will help assess your cat’s vaccination needs.

Treatment and Management of Infected Cats

There are no treatments for FeLV that will get rid of the infection. Infected cats should visit their veterinarian for regular check-ups, which will help your cat live as long as possible with good health. High-quality commercial diets are recommended, while raw food diets may cause serious infections. Your veterinarian will advise on blood testing, in addition to:


Infected pet cats should live indoors so they don’t infect other cats. Other cats in the same household should be tested for FeLV as well. In some cases, cats that live together may need to be separated to avoid the spread of infection. Your veterinarian will help you determine what the best plan is for you and your cat(s).

Stress may play a role in triggering the virus to become active again. If there are other cats in your home, or a shortage of food bowls, water bowls, and litter boxes, it may cause stress because most cats do not like to share. Keeping litter boxes, and food and water bowls clean is also important.




Your veterinarian is your partner in caring for your infected cat. With regular healthcare check-ups and a low-stress life, your cat(s) infected with FeLV may live happy and healthy for many years.