Feline Leukemia

What is Feline Leukemia Virus (FeLV)?

Feline Leukemia Virus (FeLV) is a common infectious disease in cats. It is most commonly found in environments where there are a lot of cats, like a multi-cat household and where feral cats live in a free-roaming environment.

FeLV Transmission Principles: Above photo for reference

  • Infected cats may begin to shed virus within 30 days of exposure

  • Shed in saliva

  • Less commonly shed in nasal secretions, milk, urine, or feces

  • Transmitted mainly via oral nasal route and less commonly via bite wounds

  • Spread horizontally among cats that live together or fight

  • Spread vertically and horizontally from infected queens to their kittens

  • Kittens more susceptible to becoming progressively infected than adult cats

FIV Transmission Principles: Above photo for reference

  • Infected cats may begin to shed virus within 14 days of exposure

  • Shed in saliva

  • Spread horizontally via bite wounds and FIV-infected white blood cells

  • Transmission from queens to kittens is uncommon in natural infection

  • Transmission between cohabitating cats is uncommon without fighting

  • Sexual transmission is uncommon

Signs and Symptoms of FeLV:

The signs and symptoms of FeLV vary greatly depending on the infected cells. Some cats show mild symptoms, but many cats don’t have any noticeable symptoms. Signs may include:

  • Fever

  • Unusual breathing patterns

  • Loss of appetite

  • Diarrhea, you may also notice UTI issues: constant squatting with little to no urine coming out.

  • Weight loss

  • Lethargy

  • Poor coat or fur condition

  • Enlarged lymph nodes

  • Pale gums, or a yellow color around the mouth and whites of the eyes.

  • 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

How Feline Leukemia Virus Is Transmitted?

Feline leukemia is a disease that only affects cats -- it cannot be transmitted to people, dogs, or other animals. FeLV is passed from one cat to another through saliva, blood, and to some extent, urine and feces. The virus does not live long outside the cat’s body -- probably just a few hours. Grooming and fighting seem to be the commonest ways for infection to spread. Kittens can contract the disease in utero or through an infected mother’s milk. The disease is often spread by apparently healthy cats, so even if a cat appears healthy, it may be infected and able to transmit the virus.


The virus occurs in saliva, nasal secretions, urine, feces and milk from infected cats. It is spread cat-to-cat through:

  • Bite Wounds

  • From an infected mother cat- feeding her children- the milk will contain any pathogen the mother is carrying.

  • During mutual grooming

  • Through shared litter boxes, feeding (although rare, it can happen)


  • There are two blood tests for FeLV. The first is called ELISA, which can often be done in your veterinarian’s office. This test detects FeLV proteins and can help identify an infection in the initial stages. Cats can occasionally clear the virus, so ELISA-positive cats may need to be tested again at a later time.

  • The second test is known as IFA. It is recommended for cats who are ELISA-positive, and it evaluates the progression of the virus. Cats who are IFA-positive do not normally clear the virus from their system and usually have a poor long-term prognosis.


Unfortunately, there is no cure for FeLV, but there are things you can do to help an infected cat live longer and more comfortably. For instance:

  • Treat existing health issues – If your cat has a secondary infection, they might need antibiotics, fluid therapy, or even hospitalization. FeLV can also result in some forms of cancer in which case chemotherapy might be recommended.

  • Keep your cat as healthy as possible – Since your cat’s immune system is compromised, it is especially important to maintain their health. This includes feeding them a nutritious diet and making sure they get appropriate amounts of exercise and rest.

  • Visit your veterinarian every six months – FeLV positive cats require more frequent checkups to help detect secondary infections and other health problems early when they can be easier to manage.

You should also keep an eye on your cat for physical changes like weight loss or behavior issues such as increased anxiety, irritability, or aggression. If you notice any changes that concern you, consult with your veterinarian.

Avoid Spreading the Infection

If you have an infected cat, you must take steps to avoid spreading the virus. For example, do not let the cat outside or around uninfected cats. If you have an uninfected cat already living in the home, you should separate them as much as possible. Also, make sure they have their own litter boxes, food dishes, and water bowls.