Causes of Feline Leukemia

Feline leukemia is caused by the leukemia virus (FeLV), which is a retrovirus that affects the cat's immune system. The virus can be transmitted from infected cats and can be prevented if the feline leukemia vaccine is administered. Feline leukemia is a deadly disease, but death is typically caused by a secondary infection or cancer.

Causes of Feline Leukemia

  • The feline leukemia virus can be transmitted from one cat to the other through saliva.
  • Even if a healthy cat comes in contact with a food or water bowl of an infected cat, the chances of infection are high.
  • If an infected cat grooms a healthy cat, the virus can be contracted.
  • The virus can be transmitted from mother to kitten through the placenta, or afterbirth, when the mother grooms the kitten.
  • The virus cannot be transmitted to humans, but can be fatal in infected cats.

The virus can survive up to 2 hours in a dry environment, while a moist environment will allow the virus to be alive for more than 2 days.

Feline Leukemia Symptoms

FeLV will affect the cat's immune system, making it weak, so the cat is more susceptible to diseases. In this respect, feline leukemia is similar to FIV (feline immunodeficiency virus).

Leukemia will have no typical symptoms in the first stages of the disease. The cat may have fever, be lethargic or lack appetite. The cat will start to contract different diseases, and these conditions will tend to reoccur due to the suppressed immunity.

A cat with FeLV is susceptible to:

  • Cancers
  • Respiratory diseases
  • Stomatitis
  • Gingivitis
  • Dental problems
  • FIP (feline infectious peritonitis)
  • Feline distemper

In time, the cat will lose weight and even become anemic.


The presence of the virus can be detected through a blood test. The ELISA test may be a conclusive analysis, which will indicate if there are typical antibodies or antigens that are released by the body if the virus is present.

Feline leukemia is not a treatable condition, but you must keep an eye on the cat's condition and administer treatment to all secondary diseases or infections. Fluid therapy may be needed.

You should offer your cat comfort and keep him indoors, so as to avoid other infections. There are cats with leukemia that live a normal life and can survive several years.

Cats with leukemia typically die of respiratory failure or cancer. If the cat's condition is worsening, euthanasia must be considered.


Vets recommend the administration of the FeLV vaccine to prevent contracting the virus. The vaccine is effective and unlike the FIV vaccine, won't show a false positive in blood tests.

The transmission of the feline leukemia virus can be prevented if your pet avoids contact with infected cats. If you have more than one cat and one of them is infected, you need to keep the infected cat isolated. Don't allow the cats to meet or use the food bowls of the infected cat. Keep the infected cat indoors to avoid infection of other cats.