Feline Leukemia

Feline leukemia is a viral infection that can result in immunosuppression, decreased white blood cell count, neoplasia, and, in some cases, neurologic dysfunction. It is common in the United States, affecting 2-3% of all cats.

Who Is at Risk?

It is most common in high volume situations (such as shelters) where infection status may be unknown, and in cats that are indoor/outdoor or primarily outdoor, where they are most at risk of being bitten by an infected cat. Kittens are more at risk than adult cats.

How Is Leukemia Transmitted?

Leukemia is mainly transmitted through saliva. It can also be shed in the urine, feces, or nasal secretions of affected cats. Transmission can occur during grooming between cats, through bite wounds, or, less commonly, through the sharing of items in the household (bowls, litter boxes, and toys). Placenta transmission from mother to kitten has been reported as well.

How Is it Diagnosed?

The virus is diagnosed via a SNAP test, which only requires a few drops of blood. The test can be run in minutes at your primary care veterinarian’s office.

This is an ELISA test. If this initial test shows up positive, your veterinarian may send out for additional testing to confirm active FeLV infection.

How Are Symptoms of FeLV Presented in a Cat?

• Many cats with FeLV are in a “subclinical” stage. In other words, they have no symptoms. As the infection progresses over time, clinical signs can develop. Sometimes, the signs are very mild or nonspecific, such as a nasal or ocular discharge. Weakness, lethargy, pale gums, and anemia can be seen in more advanced cases. There are different subtypes of FeLV infection and these subtypes can lead to cancer (most commonly lymphoma) or non-regenerative anemia.
• The immunosuppression that is caused by FeLV leaves the infected cat susceptible to bacteria and fungi that would not affect an otherwise healthy cat. FeLV is one of the most common causes of cancer in cats.
• Some young kittens can succumb to what is colloquially known as “fading kitten syndrome” and pass away very early in life. In this situation, if you know the mother of the kitten, it would be important to test her as well as she might be a carrier of the disease.

What Should You Do If Your Cat Has FeLV?

• If your cat has been diagnosed with FeLV, it is important that they remain an indoor cat for the rest of their lives. This not only decreases their risk of getting sick from a secondary infection from being outside, but it also minimizes the spread of FeLV to other healthy, non-infected outdoor cats. If your cat is FeLV positive with no clinical signs, no further action is needed! Just keep them inside, safe, and healthy to the best of your ability.
• If your cat has FeLV and is sick (experiencing vomiting, diarrhea, weakness, or inappetence), treatment will be based on addressing these secondary clinical signs.
• If you have a cat with FeLV as well as lymphoma, chemotherapy is still an option, however, the prognosis is worse than a cat with just lymphoma alone.
• At the moment, there is no cure for FeLV. There has been some research on using different antiviral drugs to treat cats with FeLV infection, but the long term benefits of these treatments is unclear at the moment.

What Is the Long-Term Prognosis?

Cats with FeLV can have a normal lifespan and live long, healthy lives. If they develop secondary conditions (such as anemia), the prognosis becomes more guarded. We recommend that cats who are FeLV-positive visit their veterinarian more regularly (every 6 months as opposed to annually).
If you have a cat who is considered high risk (primarily outdoor), we recommend getting the FeLV vaccine. Talk to your veterinarian and see if this vaccine would be beneficial for your cat.

FeLV is a viral infection of cats. In the early stages, infected cats may show no symptoms at all. FeLV is linked to serious diseases, most notably cancer and anemia. If your cat is high risk, it is important to get them tested annually.

Depending on time of diagnosis and overall health of the cat, patients with FeLV can live active, normal lives. Keeping them inside and making more frequent trips to the veterinarian will help the cat’s prognosis.