Feline Leukemia Virus (FeLV)


Overview of Feline Leukemia Virus (FeLV)

Feline leukemia virus, commonly abbreviated as FeLV and called “fe-leuk”, is a viral disease of domestic cats that impairs immune system function and causes some types of cancer. FeLV is transmitted by bite wounds, shared dishes or litter pans, or close contact (grooming). Kittens can be born with FeLV or acquire the virus through their mother’s milk.

Below is an overview on Feline Leukemia Virus (FeLV) followed by in-depth detailed information on the diagnosis and treatment of this condition. 

The average age of infection is 3 years and male cats may have a higher prevalence of infection than female cats. The rate of FeLV infection is higher in multi-cat households, catteries and urban areas with high cat populations. The FeLV infection rate ranges from 2 to 13 percent in the general cat population.

FeLV is destroyed in the environment within minutes. There is no evidence of transmission of FeLV from cats to humans. The course of FeLV infection is variable, and there are 3 main stages of infection.

Approximately 33 percent of FeLV-infected cats are infected briefly but are able to eliminate the virus within 4 to 6 weeks. Such transiently infected cats do not become ill or develop FeLV-related disorders.

  • Another 33 percent of FeLV-infected cats develop FeLV-related disease with approximately 60 percent mortality within 2 years.
  • The remaining 33 percent of infected cats cannot completely eliminate the virus, but do not usually develop FeLV-related disease. Such infections cannot be detected with routine blood tests, and require special diagnostic tests such as bone marrow culture of the virus or identification by a special molecular biology technique called polymerase chain reaction (PCR). In a small percentage of these cats, reactivation of the virus is possible. Latent infection also may explain development of certain types of cancers which develop in older cats.
  • FeLV-associated diseases usually are categorized as neoplastic (cancer) or non-neoplastic (include impairment of immune function and development of secondary infections).
  • What to Watch For

  • Secondary infections
  • Anemia
  • Difficulty swallowing or eating
  • Weight Loss
  • Difficulty breathing
  • Eye problems
  • Coughing
  • Lethargy
  • Poor wound healing

    Diagnosis of Feline Leukemia Virus (FeLV)

    Veterinary care should include diagnostic tests and subsequent treatments. Diagnostic tests are needed to recognize FeLV, and exclude other diseases. Tests may include:

  • A complete medical history and a thorough physical examination.
  • A screening blood test for FeLV. The most commonly performed screening tests are the ELISA (enzyme-linked immunosorbent assay) and IFA (indirect immunofluoresence) tests. Healthy cats should not be euthanized based on the results of one screening blood test.

    Treatment of Feline Leukemia Virus (FeLV)

  •  There is no specific treatment that will reliably eliminate FeLV infection. However, treatments for FeLV may include any of the following:
  • Antibiotics for secondary bacterial infections
  • Nutritional support (force feeding, tube feeding)
  • Parasite control
  • Biopsy to diagnose cancer
  • Surgery to remove tumors
  • Chemotherapy for Lymphosarcoma (cancer of the lymph nodes and tissues that produce lymphocytes)
  • Home Care

    Administer as directed any medications prescribed by your veterinarian. Provide high quality nutrition and schedule regular follow-up visits with your veterinarian to monitor your cat’s condition.

    All FeLV-infected cats should remain indoors to decrease exposure to other cats. Isolate FeLV-infected cats from FeLV-negative cats.

    Preventative Care

    Feline leukemia virus is an infectious disease that can be prevented primarily by eliminating interactions with infected cats. Recommendations include:

  • Keep your cat indoors.
  • Prevent fighting with other cats.
  • Neuter males to help decrease roaming and fighting.
  • Test other cats in the household and isolate FeLV-negative cats from FeLV-positive cats.
  • Vaccinate “at-risk” cats against FeLV. “At-risk” cats include cats that spend any time outdoors, breeding cats, or cattery cats.

    Vaccination against other diseases should be discussed with your veterinarian. If yearly vaccinations are given, only killed vaccine products (those composed of killed virus rather modified live virus) should be used to avoid complications in FeLV-infected cats with potentially weakened immune systems.

    Antibiotics should be administered to FeLV-infected cats before preventative dentistry to minimize the risk of secondary bacterial infection.

  • In-depth Information on Feline Leukemia Virus (FeLV)

    Other medical problems can lead to symptoms similar to those encountered in FeLV-infected cats. It is important to exclude these conditions before establishing a diagnosis of FeLV infection.

  • Feline ehrlichiosis (a disease caused by bacteria called rickettsia which live inside the cells of the animal).
  • Feline infectious peritonitis (FIP) (a viral infection of cats that causes fever and abnormal function of the nervous system, eye, liver, and kidneys).
  • Feline immunodeficiency virus (FIV) (a viral infection of cats similar to AIDS in humans).
  • Feline infectious anemia, also known as Hemobartonella felis (a parasite that infects the red blood cells of cats).
  • Hemolytic anemia (a disease characterized by destruction of the cat’s red blood cells).
  • Histoplasmosis (a disease caused by a fungus in the environment that can infect the lungs and other organs of pets).
  • Leukemia (cancer of the blood-forming tissues of the body).
  • Lymphoid hyperplasia syndrome (a non-cancerous abnormal proliferation of lymphocytes in the lymph nodes of the body).
  • Lymphosarcoma (Lymphoma) (cancerous proliferation of lymphocytes in the lymph nodes and other lymphoid tissues of the body).
  • Mast Cell Tumors (a tumor arising in the skin or occasionally in the spleen or intestinal tract of cats).
  • Multiple myeloma (a tumor arising from the antibody-producing cells of the body called plasma cells; also called plasma cell tumor or plasma celly dyscrasia).
  • Myeloproliferative disease (cancerous proliferation of white blood cell precursor cells in the bone marrow).
  • Cancers of tissues other than lymph nodes and bone marrow.
  • Rocky Mountain spotted fever (another rickettsial disease).
  • Sepsis (bodywide bacterial infection).
  • Systemic lupus erythematosus (a systemic autoimmune disorder affecting the skin, kidneys, joints, and blood-forming tissues).
  • Thrombocytopenia (a decrease in blood platelet concentration).
  • Thymoma (cancer of the thymus, a blood cell-producing organ found in the chest of young animals).
  • Toxoplasmosis (a disease caused by a protozoan parasite that affects the nervous system, eye, and other organs).
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