Feline Leukemia Virus

By: Dr. Carol Edwards

Most of us have heard of Feline Leukemia Virus (FeLV), a fatal and contagious disease of cats. It can cause severe and irreversible anemia, cancer, or terminal immunosuppression. One of the issues with the virus is that it can take a month to show up on a blood test. So even if your new cat or kitten has tested negative for FeLV, MAKE SURE TO RE-TEST a month later.

Transmission: Any body fluid can spread the virus. It is most commonly spread in saliva (bite wounds, shared food or water bowls, grooming each other) but can also be spread by blood, venereally, by the queen to her kittens before birth or through her milk.

Kittens are 6-7 times as susceptible to infection because of their immature immune system, and it is generally fatal for them. Infection: The virus infects tonsils and lymph nodes first, and then goes into the blood. Because this can take several weeks, a FeLV test is warranted a month or after any possibility of exposure.

Six-eight weeks after exposure, the virus goes from the bloodstream to actually enter the blood cells themselves and infect the blood cells. Once the virus is inside the blood cells, it is no longer detectable by routine testing. Specialized tests, called IFA and PCR can detect the virus. In adult cats with infected blood cells, the infection can become regressive or progressive.

Regressive Infections:

  • Most common
  • May remain latent (inactive) indefinitely
  • Generally not contagious
  • Requires a specialized REAL Time PCR test to diagnose

Progressive Infections:

  • Can result from any exposure, including Regressive Infections
  • Survival averages ~three years
  • Fatalities secondary to tumors are progressive anemia, immunosuppression, and others

As a result, we recommend FeLV testing:

  1. When you get a new cat
  2. A month after any possible exposure your new cat has had with any other cats
  3. If your cat should be exposed to any cat of unknown FeLV status
  4. If your cat should develop a new illness suggestive of FeLV, is responding poorly to treatment, or has vague, nonspecific symptoms.

If you’re ever concerned about your cat’s health, please call us at 717-697-4481.