Understanding Feline Leukemia Virus: Testing, Symptoms, and Prevention

If you are bringing in your new kitten, taking in your adult cat to the veterinarian for the first time, or have a sick kitty, you may hear your veterinary team recommend a test for Feline Leukemia Virus (FELV). This is an immune virus that effects our domesticated cats and unfortunately can have a high fatality rate. It is more common in young cats less than one year of age, which is why we recommend testing all kittens once they are over 8 weeks of age.

Effects & Symptoms

Feline leukemia weakens the immune system and dramatically increases the risk of blood and lymph cancers, leukemia, and lymphoma. The bone marrow is often affected, leading to low red blood cell counts called anemia. White blood cells and platelets are also produced there, so these are often low as well. Secondary infections are also very common due to the suppressed immune system. Upper respiratory tract infections, blood-borne infections, and autoimmune reactions are very common.

Symptoms include:

  • General malaise
  • Decreased appetite
  • Weight loss
  • Fever
  • Enlarged lymph nodes

Early in the progressive infection, there are generally no symptoms. Blood work varies from no abnormalities to changes in white and red blood cell counts, abnormal liver or kidney values, and abnormal protein levels.

Treatment

Unfortunately, there is no effective treatment. Symptoms can be attempted to be controlled with antibiotics, nausea medications, appetite stimulants, and sometimes steroids. However, there is an effective vaccine that is recommended to cats based on their individual environment and their potential for exposure. Young cats, less than 1-2 years of age, but especially less than 3 months of age are very susceptible. As cats age, they develop a much stronger natural immunity. We currently recommend vaccinating all kittens for the virus, and continuing that in adult cats that roam outdoors or live with FELV positive cats.

When testing for the virus, there are a few different tests that may be recommended. Typically, we start with an in-house or send-out ELISA test. This is a quick test (10 minutes in-house) that is used as a screening test. If this test is positive, then a confirmatory test is usually recommended, either immediately or in a few months. To further understand why that is, let’s talk about the different types of infections that can happen.

Types of Infections 

A progressive infection is the serious and most often fatal form of the disease. A cat becomes exposed and the virus is able to replicate and take hold in the lymph nodes, bone marrow, and internal organs. Eventually, usually by 3 years of age they will begin to show symptoms from the leukemia virus.

A regressive infection type includes the cat becoming infected, and the virus being able to replicate. The cat then mounts a strong immune response and is able to dramatically reduce the amount of virus in the body. A very small amount remains in the bone marrow and becomes difficult to detect. Cats in this category may become progressive or may never show symptoms of the disease. As time passes, progress becomes less likely.

An abortive infection type consists of the cat being able to fight off the virus and is not allowed to take hold or cause a serious infection.

It is important to be familiar with the types of infections when testing. A positive ELISA (screening test) indicates active infection. This could be a progressive infection or a cat in the infection stage of either the regressive or abortive type. In order to determine if this is the case, repeating the ELISA test in 1-3 months can be done in healthy cats. With a positive ELISA test, a confirmatory test should be run to determine if they have the progressive vs regressive type. The two confirmatory tests that can be run are IFA and PCR. Both are able to determine progressive vs regression type with about 90-95% confidence.

If you have any questions or concerns during this time, please do not hesitate to contact us here at Metro Paws Animal Hospital. We are always happy to help you!