Feline Leukemia Virus
Feline leukemia virus (FeLV) is the leading viral killer of cats, affecting 2-3% of cat in the United States. FeLV causes blood disorders and is the most common cause of cancer in cats. Most substantially, it weakens the immune system, increasing the likelihood of invasion of opportunistic infections. An opportunistic infection is caused by pathogens that take advantage of an opportunity to infect a host, such as an already weakened immune system. Due to the weakened immune system and opportunistic infections, common bacteria that usually do not affect healthy cats can cause severe illness in FeLV infected cats. Infection rates of FeLV are significantly higher (about 30%) in cats that are already ill.
Feline leukemia virus is extremely contagious and can be passed by saliva, nasal secretions, urine, feces, and milk of an infected cat. Cat-to-cat transfer can occur through a bite wound, mutual grooming, and more rarely through shared litter boxes and feeding dishes. FeLV can only survive for several hours outside of a host, therefore a more direct transmission is typically required.
Cats that are most susceptible to the virus would be ones that are exposed to many other cats. For example, either cats that were adopted from shelters or cats that are allowed outside unsupervised would be at a higher risk than singular indoor house cat. Additionally, kittens are more susceptible to contracting FeLV than adult cats. That being said, even healthy adult cats can contract the virus.
The progression of feline leukemia virus in a cat can be prolonged and concealed. Cats may have no signs during early stages, then over weeks, months or even years the cat’s health will begin to progressively deteriorate. Symptoms of a cat infected with FeLV might include weight loss, lethargy, fever, diarrhea, abnormal breathing patterns, and poor coat condition. There are two different blood tests that can be done to diagnose a cat with FeLV. An enzyme-linked immunosorbent assay (ELISA) is typically the first test that is done and can be conducted at most vet offices. After a positive ELISA result the next step would be conducting an indirect immunofluorescent antibody assay (IFA).
The good news is there is a relatively effective vaccine to protect cats against FeLV. The vaccination is not 100% affective, however paired with limited exposure to infected cats is the best preventative measures to take. Owners that are considering the FeLV vaccination for their uninfected cat should discuss advantages and disadvantages bases on a case-by-case evaluation with their veterinarian. A confirmed diagnosis can be an intimidating reality for cat owners. However, it is important to realize that cats with FeLV can live normal lives for prolonged periods of time. Average life expectancy after a diagnosis is 2.5 years. With careful monitoring and management of symptoms the cat can continue to grow in a loving home.