Feline Leukemia Virus

From WikiVet English
Jump to navigation Jump to search



  • Main envelope protein: gp70
  • 3 antigenic subgroups:
  • Group A
    • is transmitted between cats
    • is monotypic: one vaccine covers all isolates
    • causes lymphosarcoma
  • Group B:
    • is recombinant with transmissible FeLV-A
    • increases the chance of thymic tumors
  • Group C:
    • is a mutant of A
    • isolates are rare, and occur as A+C mixtures
    • increases chances of anemia


  • FeLV is the "disease of friends": transmission usually occurs through mutual grooming
  • From the oropharynx, virus spreads to most tissues in the body to replicate, notably:
    • Bone marrow
    • Thymus
    • Salivary glands
    • Reproductive tract
  • Most kittens but only 30% of adults become viremic for life without producing antibody
    • 20% of viremic cats die of tumors
    • 30% of viremic cats die of FeLV-associated disease
    • 80% die within three years of exposure
  • 30% of adults exposed become latently infected and can become viremic when immunosuppressed
  • 40% of exposed adults remain healthy and develop Ab and CD8+ Tcells after clearing the virus, without becoming reinfected or silent carriers

Clinical Signs:

  • Leukemia
  • Multicentric lymphosarcoma: B or T cell tumors, which may be palpable as enlarged lymph nodes (particularly mesenteric)
  • Thymic lymphosarcoma: T cell tumors, with only the thymus enlarged
    • Results in dyspnoea
    • Confirmed by radiography
  • Alimentary lymphosarcoma: B cell tumors of the Peyer's patches

FeLV-associated disease:

  • Immunodepression causing secondary disease
  • Reproductive failure: FeLV crosses the placenta, causing fetal resorption or viremic kittens with thymic aplasia


  • Vertical transmission of FeLV-A from mother to kittens either via placenta, grooming, or milk
  • Horizontal transmission occurs via saliva during mutual grooming
  • Recovery linked to age and presence of maternal antibody
  • Particular concern for intensively bred cats because of crowding, etc.


  • FeLV should be suspect in any cat with recurrent bacterial infections, anemia or weight loss
  • ELISA for Antigen (capsid protein p27 or envelope protein gp70)
  • Immunochromatography is now trusted as ELISA testing can give false positives
  • Virus isolation from heparinised blood can now be performed to confirm a positive diagnosis


  • Antigen positive sick cats should be destroyed
  • Healthy positive cats should have diagnosis confirmed
  • Vaccination:
    • Should take place once antigen-negative status has been determined
    • Leukogen: Subunit vaccine (using envelope protein gp70) produced in E. coli mixed with Quill-A and alhydrogel
    • Others include inactivated virus and canarypox recombinants, but all MUST include FeLV-A