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Feline leukemia virus (FeLV) is a contagious disease spread between cats. It is transmitted through virus-infected saliva via bite wounds, mutual grooming or shared food/water dishes. Cats that spend time outdoors (in contact with feral cats) and cats living in multi-cat households are at the highest risk of contracting FeLV. Kittens can also become infected through their virus-carrying mother.

Once the cat becomes infected, the virus will take one of several courses:

The immune system functions at a high level to force the virus into latency. In these cats, clinical signs are not persistent or severe initially, and they may become carriers of the virus. These cats have the potential to become clinically ill in the future.

The immune system is unable to adequately fight the virus and the virus persists in the tissues and causes clinical signs. These cats are persistently ill.

FeLV suppresses the immune system and can cause bone marrow cancers. FeLV itself is not a fatal virus, but secondary infections from immunosuppression and neoplasia (cancer) can result in death. The onset of FeLV-related disease usually occurs months to years after infection.

Common Clinical Signs:

These signs will vary depending upon the state of the patient’s immune system, primary organ/system affected, concurrent diseases, etc.

Enlarged palpable lymph nodes

Chronic nasal/sinus irritation, ocular discharge, conjunctivitis

Persistent diarrhea

Chronic gingivitis

Non-responsive or recurrent skin/ear infections

Weight loss


Diagnosis of FeLV infection is fairly straightforward. The test can be run in the clinic, requires only a few drops of blood and takes 15 minutes to run. More diagnostic tests (baseline bloodwork, radiographs, etc.) may be indicated to uncover concurrent disease.


Treatment is extremely dependent upon concurrent disease. Supportive care and management of secondary infections are the mainstay of therapy to increase the quality of life of the patient. Drugs to stimulate the immune system may also be helpful in some cases.


Long term prognosis for a FeLV positive cat is poor. They generally develop either bone marrow cancer or succumb to secondary infections due to immunosuppression. This may occur within months to years of the original infection. The short term prognosis and quality of life for these animals is extremely variable depending upon the individual case.

If your cat is FeLV positive, all other cats in the household should be tested. FeLV positive cats should not be allowed contact with any other cats to eliminate the possibility of transmitting the virus.


All new cats/kittens being introduced into a household with existing cats should be tested for FeLV and FIV (feline immunodeficiency virus) BEFORE they are introduced into the household. Cats that are at a high risk of contracting FeLV (indoor/outdoor cats, multi-cat households) should be vaccinated against FeLV.

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