Feline Leukemia: Testing Your Cat for the Feline Leukemia Virus

Aug 20, 2011
Lorie Huston

Testing cats for the feline leukemia virus can be somewhat complicated. - pinguino/Flickr.com

The most commonly used test for feline leukemia is the ELISA test. However, if your cat has a positive ELISA test, your veterinarian may advise an IFA test.

Feline leukemia (FeLV) is a contagious viral disease that can be passed from one cat to another. Because of the contagious nature of the disease, testing for feline leukemia is generally recommended for all cats.

When Should Your Cat Be Tested for Feline Leukemia?

In general, if you do not already know your cat's feline leukemia status, he should probably be tested. Feline leukemia can produce symptoms that mimic many other diseases in an infected cat. For this reason, feline leukemia must be considered as a potential cause for the illness of any sick cat. Testing is the only way to know whether your cat is infected with feline leukemia or not.

The American Association of Feline Practitioners (AAFP) has published a set of guidelines listing specific circumstances under which testing for FeLV is recommended.

How Does Testing for the Feline Leukemia Virus Work?

The most commonly done test for the feline leukemia virus is known as the ELISA (enzyme-linked immunosorbent assay) test. The ELISA test checks for the presence of antigens for the virus. An antigen is a foreign body, which in this case is part of the feline leukemia virus, that stimulates an immune response by the body.

The ELISA test is easily performed with only a very small sample of blood. The ELISA test for FeLV is frequently combined with tests for the feline immunodeficiency virus (FIV) and the feline heartworm antigen. The test can usually be performed in the veterinary clinic with results available within a few minutes.

The ELISA test for feline leukemia can also be performed using saliva or tears but testing a blood sample produces a more accurate test result with fewer false positive or false negative tests.

What If My Cat Tests Positive for FeLV on the ELISA Test?

If your cat tests positive on the ELISA test for feline leukemia, your veterinarian might recommend one of two things, depending on the circumstances.

Cats that test positive on the ELISA test should have the test repeated in 60 days. It is possible for a cat to mount an immune response sufficient to clear the feline leukemia virus, which should result in a negative test.
If the ELISA test remains positive, an IFA (immuno-fluorescent antibody) test will be performed to confirm the infection.
Alternatively, the IFA test may be performed immediately, rather than waiting to recheck the ELISA test in 60 days.
If the ELISA test is positive but the IFA test is negative, both tests should be performed again in 60 days.
If both the ELISA and the IFA tests for feline leukemia are positive, your cat is likely persistently infected. He may also be a carrier, capable of passing the disease on to other cats.