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Feline Leukemia Virus (FeLV)

Reviewed by Missy Beall, DVM, PhD on Thursday, August 14, 2014
Posted December 20, 2011 in Cat Diseases & Conditions A-Z

Adult cat being held

Feline leukemia virus (FeLV) causes a highly contagious and potentially fatal retroviral infection that weakens a cat’s immune system, making her susceptible to illness and secondary infection. Feline leukemia is a very common disease. It is often called the “friendly cat” disease as it is commonly spread from cat to cat through casual contact, such as grooming or sharing food or water. Feline leukemia virus and Feline immunodeficiency virus (FIV) are among the most common infectious diseases in cats. FeLV is nothing to meow about! In a study of more than 18,000 cats, 2.3% of them were positive for FeLV.

While all cats are at risk, lifestyle, sex, and vaccination status all play an important part in reducing exposure to this contagious disease. The following will increase your cat’s risk of contracting FeLV:

  • Not having been vaccinated against feline leukemia
  • Spending time outside, unsupervised
  • Exposure to a cat or kitten whose infection status is unknown
  • Living in a multiple-cat household
  • Not having been spayed or neutered
  • Aggressive behavior toward other cats
  • Symptoms of oral disease
  • Past or present abscess wounds

Cats with feline leukemia do not always appear sick! In the early stages of the disease, most cats show few signs; the only way to know for sure if they are infected is through a simple blood test. As the disease advances, the following symptoms may occur:


Most veterinarians include a screen for feline leukemia as part of the routine tests a cat gets during her lifetime. The American Association of Feline Practitioners (AAFP) recommends testing cats for FeLV as follows:

  • Cats should be tested at appropriate intervals based on their risk
  • Cats and kittens entering a new household should be tested at introduction 
  • Cats exposed to an infected cat should be tested twice—at the time of exposure and 60 days later
  • Cats should be tested before they are vaccinated for FeLV
  • Cats with clinical signs should be tested

Your veterinarian can run a simple test to see if your cat has been infected with FeLV. If the result is negative, they may recommend protecting your cat from FeLV by having her vaccinated. The AAFP recommends vaccinating all kittens (because their future lifestyle may change), cats that go outdoors, cats that have direct contact with cats of unknown status, and

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