What is Feline Leukemia?

Cat Leukemia

The Disease Itself

Feline Leukemia Virus also known as FeLV is one of the most common infectious diseases in cats. FeLV belongs to the group of viruses known as the “oncornaviruses”. Oncornaviruses are a group of viruses that cause the development of tumours. FeLV only affects cats. Cats infected with FeLV can develop lymphoma, leukemia and other tumours. Immunosuppression and anaemia are other effects caused by the virus. A recent study has shown that it is estimated that 80-90% of infected cats die within 3-4 years of being diagnosed with FeLV

This virus can be spread through nasal secretions, saliva, faeces and milk of infected cats. Cats may also become infected if they receive a bite wound from an infected cat, during mutual grooming. Though rare this virus may also be spread through shared use of food bowls and litter trays. Feline Leukemia may also be transmitted to kittens from infected mothers while nursing or before they are born. If exposed, kittens are at a greater risk of becoming infected if exposed, however healthy adult cats can also become infected.

Recent studies show that 1-2% of healthy cats are infected with FeLV, with the infection being more commonly found in sick/outdoor cats.


Clinical signs:

FeLV can affect our felines body in many ways. FeLV is one of the most common causes of cancer along with causing various blood disorders and immune deficiencies. With weakened immune systems and various blood disorders viruses, bacteria and fungi can cause severe illness to FeLV-infected cats more than they would healthy.

Other signs include:

  • Loss of appetite
  • Poor coat
  • Pale gums
  • Progressive weight loss
  • Enlarged lymph nodes
  • Infections of the skin
  • Infections of the bladder
  • Infections of the gums
  • Infection of the respiratory tract
  • Diarrhoea
  • Seizures
  • Eye conditions
  • Neurological disorder


Some cats will not exhibit signs during the early stages of infection. However, over time the cat’s health may deteriorate rapidly.



Fortunately, our clinic offers readily available diagnostic tests. These tests are quick and generally reliable. Occasionally false positive and negative results may occur, for this reason if an unexpected result is obtained, a confirmatory test is usually performed. Re-testing is required 12-16 weeks to confirm that patient’s status.

There are two types of blood tests commonly used within veterinary practice to diagnose FeLV. Test 1 is called an enzyme-linked immunosorbent assay (ELISA). This specific test is usually carried out first as a screening tool as it detects the presence of free FeLV particles commonly found in the bloodstream during early and late stages of infection.

Test 2 is the indirect immunofluorescent antibody assay (IFA). This test is sent to the diagnostic lab after there is a positive test for ELISA, to determine whether the animal has reached the later stage of infection. This test detects the presence of virus particles in white blood cells. Studies show that the majority of felines tested positive for IFA remain infected for the remainder of their lives.



Unfortunately, there is currently no cure for FeLV. Management and supportive therapy is highly recommended for infected patients. Such actions include:

  • Early diagnosis and treatment of secondary infections.
  • Maintaining high quality nutritional support
  • Keeping infected cats indoors to prevent the spread of the virus.
  • Routine veterinary visits with regular worming and flea treatment and vaccinations.
  • In severe cases blood transfusions and chemotherapy



Vaccination – There is a relatively effective vaccine against FeLV available in our clinic. The FeLV vaccine has been proven to be successful. As mentions earlier, kittens are at a greater risk of becoming infected, for this reason it is recommended that you routinely vaccinate your kitten against FeLV.

If you are considering vaccinating your pet you should also consider the cats risk of exposure to FeLV infected cats and discuss the advantages and disadvantages of the vaccination with your vet.

Another way to prevent and protect your cat is by keeping them indoors, away from potentially infected cats, if outdoors- ensuring they have a secure enclosure. Any cats coming into contact with infected cats should be tested prior to introducing them into a home, reducing the risk of exposing infection free cats. Food bowls and litter trays should be not be shared between infected and healthy cats. Unfortunately, FeLV positive cats are not diagnosed until after they have lived with other cats, in such cases all cats in the household should be tested. Since not all cats will be protected by the vaccination preventing exposure remains important even for vaccinated pets.



The prognosis for infected cats remains guarded. It is important to realize that cats infected with FeLV can live normal lives for prolonged periods of time. Studies show that the median survival time after diagnosis is 2.5 years. Careful monitoring of appetite, weight, behaviour, urine and faeces output, appearance of eyes and mouth are key elements in managing this disease. Should there be a change in any of these areas, immediate consultation with your vet is required.