Feline leukemia

Feline leukemia virus (FeLV) is a virus that can be transmitted between cats via saliva or nasal secretions and causes cancer of the blood cells.

How can my cat get feline leukemia?

Any cat is at risk of infection if it is exposed to an infected cat. Mutual grooming and bites pose a risk of transfer of the virus. The virus may also be spread through feces, urine, and milk of an infected cat. Feline leukemia virus does not survive for more than a few hours outside the cat's body.

Kittens and cats with weakened immune systems face the greatest risk of infection. According to Cornell University College of Veterinary Medicine, "the degree of virus exposure sufficient to infect 100% of young kittens will infect only 30% or fewer adults." However, healthy adult cats may still become infected with sufficient exposure to the virus.

What are the signs?

The feline leukemia virus inserts its genetic code into infected cells and can cause various blood disorders which weaken the cat's immune system from protecting against bacteria and viruses found in the everyday environment.

Signs include:

  • Loss of appetite

  • Weight loss

  • Pale gums

  • Fever

  • Poor coat condition

  • Diarrhea

  • Vomiting

  • Lethargy

  • Seizures and neurological disorders

There are two stages of FeLV. During primary viremia, some cats' immune systems are able to fight off the infection and prevent progression to secondary viremia. In this secondary stage, the bone marrow and other tissue have become infected with FeLV and the condition has passed the point of no return. In other words, the cat's immune system can no longer rid itself of the virus at this point.

How is it diagnosed?

There are two common types of blood tests to detect protein components of the virus. Enzyme-linked immunosorbent assay (ELISA) tests can be performed at your veterinary hospital and can detect both primary and secondary stages of viremia. The other type of test, indirect immunofluorescent antibody assay (IFA), must be sent to a diagnostic lab and only detects secondary viremia.


The best way to prevent your cat from becoming infected with FeLV is to keep them away from infected cats. There is a FeLV vaccination available which you may discuss with your veterinarian, however not all vaccinated cats are protected against FeLV.


Feline leukemia virus weakens a cat's immune system and predisposes them to a variety of diseases and infections. Unfortunately there is no cure and actively infected cats generally live for a maximum of three years.

The ideal environment for an FeLV positive cat is indoors to prevent potential secondary bacterial, viral, or fungal infections. Avoid feeding raw or undercooked foods due to the risk of food-borne bacteria. Be sure to schedule veterinary check-ups every 6 months for a thorough examination of all of your cat's body systems.

Source: "Feline Leukemia Virus (FeLV)." Cornell Feline Health Center. Cornell University, College of Veterinary Medicine, n.d. Web. 04 June 2013.

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