Frequently-Asked Questions

What is feline leukemia?

How did FeLV originate?

Is FeLV contagious?

Can I catch FeLV from my cat?

Can I transfer FeLV TO my cat?

How is FeLV transmitted?

Are some cats more susceptible than others?

What happens if my cat is exposed to FeLV?

How does FeLV infect a cat?

What are FeLV symptoms?

What is an FeLV "carrier?"

What is an FeLV "latent" carrier?

Is there a cure for FeLV?

How is FeLV different from typical viruses?

Can I test my cat for FeLV?

My cat is tested. What's next?

Can I vaccinate my cat against FeLV?

My cat has FeLV symptoms. What can I do?

What if my cat has no symptoms but tests positive?

My cat may be a latent carrier. What should I do?

How can I protect my cat from FeLV?

Feline leukemia (FeLV) is a complex disease that blocks cats' natural ability to fight off germs. It does not yet have a cure. Most cat owners are familiar with this deadly disease, but many are unaware of how serious it is.

Now cat owners have more options because researchers have discovered so much about FeLV. Your cat's life depends on your efforts to fight the disease. The more you know about FeLV, the better your strategy will be.

The Rise of the Opposition

Feline leukemia most commonly is transmitted through saliva, but it also is transferred through urine and feces.

Some cats are more likely to become actively infected than others. Those who spend part or all of their time outdoors also are at high risk, because the more time a cat is outside, the more chances it has of contacting an infected animal.

Age also affects cats' vulnerability. Kittens are less able to fight FeLV because their immune systems are not fully developed. Cats more than 10 year old also are more susceptible because their immune systems are weaker.

The Line of Attack

Feline leukemia goes through several stages after entering a cat's eye and nose membranes, says William D. Hardy Jr., V.M.D., of Cornell University. It first travels to lymph nodes in the throat, where it begins to reproduce, infecting the cat's white blood cells.

Eventually the virus enters the bone marrow and contaminates the cat's growing blood cells. Circulating blood then carries the virus to the salivary glands, respiratory cells, and urinary tract. About 56 days after invading its host, the virus becomes present in the cat's saliva and urine, and can be passed to other cats.


After it is exposed to the disease, a cat's system could react in different ways. About 40 percent of exposed cats - usually those who are healthy and stress-free - manage to destroy the disease and become immune to it. The other 60 percent divide into carriers and symptomatic cats:

  • In carriers, the immune system weakens the virus enough that it doesn't make the cats sick. Because of the lack of symptoms, an owner of an FeLV carrier probably will not realize that the cat has the virus. Meanwhile, the carrier cat can infect other cats because the virus is contagious. Carrier cats also are more vulnerable to other germs because their immune systems are busy fighting FeLV.

  • Symptomatic cats receive the full force of the infection and die in three months to three years. These cats are victims of three different conditions:

    1. First, FeLV causes various cancers by entering and changing body cells.

    3. The second condition occurs when the cat's total number of blood cells decreases, causing anemia and slower clotting.

    5. The last devastating condition is the suppression of the cats' immune systems.

Symptomatic cats may not show any physical signs right away and may inadvertently pass the disease to other cats. Until symptoms start to appear, clinical testing is the only way to detect feline leukemia.

A Short Defense

Although we do not have ways to stop the disease, veterinarians can control secondary infections with antibiotics, anemia with blood transfusions, and cancers with chemotherapy. Unfortunately, repeated treatment is expensive and does not completely alleviate a cat's suffering. Instead of prolonging the inevitable, many owners of actively infected cats opt for euthanasia.

Before scientists could vaccinate against FeLV, most veterinarians recommended euthanasia for FeLV-positive cats whether or not they had symptoms. This policy was meant to control the spread of the disease. Now that we have a vaccine, owners have the option to keep their infected cats if the cats are not suffering. If making such a decision, an owner must isolate the infected cat as much as possible because carriers can still pass the disease to unvaccinated cats.

Fighting feline leukemia involves three steps:

  • Testing
    Six years after FeLV was discovered, researchers developed a blood test to determine the presence of the virus. Veterinarians generally test cats for FeLV before vaccinating them. (Vaccinating an infected cat will not stop the infection and will give the owner a false sense of security. Testing is especially important if a cat commonly goes outdoors, is frequently sick or lives with more than one cat.

  • Vaccinating
    The FeLV vaccine provides cats with 80 to 90 percent protection from contracting the disease. The vaccine must be re-applied yearly in order to stay effective.

  • Isolating
    Isolating picks up where testing and vaccinating leave off. To cover the vaccine's protection gap, isolating the cat from unknown cats will reduce chances of exposure and help the vaccine work as thoroughly as it can.

Winning the War

By staying current with your cat's yearly vaccines and keeping it away from unfamiliar cats, you can give your feline friend the best chances possible for an FeLV-free life.

For more information about feline leukemia and cat care in general, visit Web Resources For Cat Lovers.