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Feline Leukemia Virus

Veterinarian Reviewed on June 17, 2012 by Dr. Janice Huntingford

Feline Leukemia Virus (FeLV)

The Feline leukemia virus is a retrovirus that can infect cats and causes many other diseases and complications. Other than leukemia, this virus can cause other types of Cat Cancer and countless other diseases that can harm your cat.

Since it is a retrovirus, it is specific to the feline species. This means that an infected feline can only infect another feline, not humans or any other species.

This electron micrograph depicts the retrovirus, Feline Leukemia Virus (FeLV).


This virus isn’t very common, only about 1-2% of all domestic cats will be infected with the virus. Male cats are more prone to contracting the Feline leukemia virus than females, and kittens are substantially more susceptible to the virus than adults. Also, cats that have any access to the outdoors are more likely to become infected with the virus than indoor cats.

The virus can be transmitted very easily, especially in a multi-cat household. A fairly large amount of the virus can be passed through the salvia of an infected cat, so any cats around it are at risk of contracting it. The most common way for the feline leukemia virus to be transmitted is by mutual grooming. Sharing food and water bowls can also be sites of transmission. The virus can also be excreted in tears, urine, feces, and breast milk.

Although there are many sites of transmission, it takes a substantial amount of the virus to be transmitted for another cat to be infected. So, a bite or prolonged contact between cats is needed for the virus to be transmitted.


If a cat is exposed to the virus, there are several things that can happen from that point forward:

The first is that the cat will not become infected at all. This can be due to in inadequate amount of exposure to the virus or an excellent response of the immune system of the cat. Therefore it is always a good idea to help keep your cat’s immune system in top shape.

Another thing that could happen is that an exposed cat will become infected, but develop a latent infection, which is an infection that is omnipresent, but it will be held in check by the immune system. Usually, a cat with a latent infection will not exhibit any symptoms or excrete the virus.

Unfortunately, some cats will not be so lucky. The cats that don’t develop a strong immune system to fight off the feline leukemia virus will be permanently infected. These cats will most likely develop other diseases that are associated with the feline leukemia virus and they will be able to transmit the virus to other cats.

Causes and Symptoms

There are many different diseases and complications associated with this virus, but the most common include : Cat Infectious Anemia, Cat Cancer, Cat Lymphoma Cancer, fever, weight loss, eye problems, respiratory issues, and reproductive complications.

Since so many different diseases are caused by the feline leukemia virus, the signs of infection vary greatly. Weight loss, fever, loss of appetite, and weakness are the most common indicators.

Prevention and Treatment

To determine whether your cat has become infected, you should take him or her to your veterinarian immediately. No test is 100% positive, but the virus can be detected. Once it is detected, it needs to be managed. There’s no cure, but treatments, such as chemotherapy and other holistic treatments, have been effective.

To prevent your cat from contracting this virus, you should make sure it has regular visits to its vet. It should also receive vaccines for protection and you should limit its exposure to strange cats, especially if they seem ill.

Read also: Cat Fleas
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Our Expert

Dr. Janice Huntingford
Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan

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