FLV Feline Leukemia

feline leukemia virusWhen it comes to illnesses that prove fatal to our beloved cats, Feline Leukemia Virus is top of the list. The only thing that kills more cats than this illness are accidents and trauma and FLV kills 85% of the cats that are persistently infected within three years of contracting the virus. It is doubly dangerous because it suppresses the immune system and this leads to cats also being vulnerable to deadly infections.

The good news is that having FLV doesn’t have to mean death – around 70% of cats who get the virus can resist it or even get rid of it on their own. However the more we understand the symptoms and treatment of the condition, the more we can help them.


FLV is a cats only disease that cannot transmit to humans, dogs or any other type of animal. It passes from one cat to another by contact with saliva, blood or, to a lesser extent, urine and faces. The virus doesn’t have a long lifespan when outside the cat’s body and lives for only a few hours so grooming or fighting are the most common methods of transmission. Kittens can also contract the virus from their mother in utero and through infected milk. The disease can be spread by cats that appear healthy, so there is no visual way of knowing for certain if a cat has the disease or not.

Young kittens and cats are most at risk of contracting FLV as it seems with age comes a greater resistance to the virus. Indoor-only cats are at a very low risk of catching it while cats in a multi-cat household or living in catteries are at a greater risk, particularly if they share water, food or litter trays with other cats.

While only 3% of indoor cats get FLV and this rate increases for outdoor cats, the overall infection rate has decreased significantly over the last 25 years due to reliable testing and vaccination programs.


A cat that has been infected with FLV may display any of these symptoms:

  • Pale gums
  • Yellow colouring in the mouth or the whites of the eyes
  • Enlarged nymph lodes
  • Infections of the upper respiratory tract, bladder or skin
  • Loss of weight or appetite
  • Loss of coat condition
  • Weakness and lethargy, often progressive
  • Fever
  • Diarrhoea
  • Difficulty in breathing
  • In unsprayed female cats, reproductive problems


To diagnose the condition, your vet will use a blood test called ELISA, which recognises the proteins in the blood connected to FLV. It is a very sensitive test and can diagnose cats who have only recently become infected. It is also possible for cats to clear the infection themselves and test clear a few months later.

The other test used is an IFA, which detects what stage the illness has reached. Usually this is used when cats haven’t naturally cleared the virus themselves and is conducted at a lab, rather than at the vet clinic. Cats that are given an IFA test are usually in a bad way and have a poor long-term prognosis.


85% of cats that are persistently infected by FLV die within three years but even these cats can have a good quality of life for a long time. They will also need help to avoid secondary infections due to their suppressed immune system. All cats with FLV should be neutered and kept indoors.

There is no cure for FLV apart from the cats’ body naturally fighting off the infection. Treatment can be given for secondary infections and if a cat developed cancer at the same time, they can still receive chemotherapy.


There is no guaranteed way to protect your cat again FLV as they could have received the virus from their mother before they were born. But you can reduce the risk by keeping them indoors most of the time and monitoring their general health with vet check-ups. If your cat doesn’t have the virus, it is advisable to have them vaccinated to reduce the risk of getting it in later times.

If you are introducing a kitten to a multi-cat household, they should be tested before doing this and if any of the cats already in the house have the virus; it is inadvisable to introduce another, young cat as they have a high chance of contracting the illness.


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