What is Feline Leukemia Virus (FeLV)?

Feline Leukemia Virus (FeLV) is a type of virus called a retrovirus that can infect cats. FeLV cannot be transmitted to dogs or humans.

Many cats that are exposed to FeLV and initially test positive for FeLV will mount an effective immune response that suppresses the virus (called regressive infection); these cats will test negative on subsequent tests, do not have symptoms of FeLV, and are at low risk of transmitting the disease to other cats. Cats that are unable to suppress the virus with their immune systems (called progressive infection) repeatedly test positive for FeLV, are at a higher risk of developing FeLV-associated illness, and can shed virus (and thus be contagious to other cats).

How is FeLV Spread?

FeLV is spread by close contact with other cats. The primary mode of infection is through saliva—mutual grooming, fighting, and (rarely) sharing dishes can transmit infection. An infected mother cat can spread FeLV to her kittens during birth or nursing. Kittens are more susceptible to FeLV infection than adult cats due to their immature immune system.

The FeLV virus cannot survive for very long in the environment, so cats that do not have close contact with an infected cat are unlikely to be exposed to infectious virus in the environment. The virus is easily inactivated by common disinfectants and can’t survive in a dry environment.

How is Infection Diagnosed?

FeLV is detected by a blood test that can be done at your veterinarian’s office. There are several types of test for FeLV — the most common one is called an ELISA test. Other tests, such as IFA or PCR, are used in certain cases to determine the extent of infection. The IFA test reveals true, progressive FeLV infection in the body, not just exposure to the virus.

Is There a Vaccine to Protect Against FeLV?

Yes, there is a vaccine against FeLV available for use in cats and kittens. The vaccine is not beneficial if your cat is already infected with FeLV. The vaccine can protect against progressive FeLV infection when it is given to an FeLV-negative cat and administered correctly as an initial series with annual boosters. No vaccine is 100% effective at preventing infection and disease. The recommendation to vaccinate for FeLV is based on individual risk factors (e.g. access to outdoors, age, lives with FeLV+ cat), as recommended by your veterinarian.

How Long Can I Expect my FeLV+ Cat to Live?
And What are the Symptoms?

It is impossible to predict the life span of any cat, regardless of their current health status. Cats with regressive FeLV infections can remain healthy for a normal life span; however, in rare cases, administration of drugs that suppress the immune system or illnesses that compromise the immune system can cause reactivation of the virus, leading to progressive FeLV infection in some cats.

Cats with progressive infection have a higher risk of developing life-threatening illness, which can appear as soon as 2-3 years after infection. Median survival time of progressive FeLV-infected cats is 2.4 years (compared to 6.3 years for FeLV-negative cats), but they may live up to 8 years. FeLV most often causes illness by damaging the immune system, putting cats at risk of opportunistic infections and certain types of cancer. While there is no cure for FeLV infection, supportive care for illnesses caused by FeLV can improve length and quality of life.

Can an FeLV+ Cat Live With Other Cats?

It is the sole responsibility of the adopter/guardian to make the decision to house an FeLV-positive cat with an FeLV-negative cat. We recommend discussing with your veterinarian the best strategies to reduce risk when introducing an FeLV-positive cat to a multi-cat household, including vaccination of resident cats. Because FeLV can be transmitted through casual contact, an FeLV-negative cat could be exposed to FeLV if the cats have close interactions such as mutual grooming, sharing litterboxes, or fighting. In households where non-infected cats are effectively vaccinated for FeLV, the risk of the non-infected cats developing progressive infection is very low.

How Should FeLV+ Cats be Managed?

Any cat that has tested positive for FeLV should be kept indoors at all times and provided with good nutrition, a low stress environment, and regular veterinary care. Regular veterinary care includes vaccinations and wellness exams every 6-12 months, in addition to regular laboratory testing as recommended by your veterinarian. Because FeLV can weaken the immune system, your veterinarian may recommend more aggressive treatments and testing, even for mild illnesses, as a precaution to safeguard your cat’s health.

Why Should I Adopt an FeLV+ Cat?

FeLV-positive cats are just like other cats. They all have unique personalities and traits and will provide you with love, laughter, and companionship.  

People Rescuing Animals … Animals Rescuing People®

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