Feline Leukemia Virus Testing

Feline leukemia virus (FeLV) testing is a simple, but important, part of cat ownership. Two types of blood test are available to screen your cat for exposure to this deadly disease. The first test can be conducted at your veterinarian's office, while the second one requires the use of a diagnostic laboratory to determine the results.

The ELISA Test

The enzyme-linked immunosorbent assay, or ELISA, test is the one your veterinarian can perform on-site. It detects FeLV in both the primary and secondary stages and is the first line of FeLV testing that most veterinarians use.

The ELISA test screens for the presence of viral antigens in the blood, which means that it can determine whether your cat has been exposed to FeLV. However, exposure does not necessarily mean your cat will contract FeLV, so it's important to retest your pet if she has a positive ELISA test.

To ensure your cat's health, make sure her blood is screened with the ELISA test. In the past, tests have sometimes been performed using tears or saliva, and the results are not as reliable with these bodily fluids as they are with blood.

If your cat receives a negative ELISA test but you believe she has been exposed to FeLV, have her retested in a month to protect her long-term health.

The IFA Test

If your veterinarian receives a positive result on your cat's ELISA test, he or she will retest your pet using an indirect immunofluorescent antibody assay, or IFA, test. This test detects only the secondary stage of FeLV, so a positive result on this test means that your cat has FeLV. The results of this test will be determined at a diagnostic laboratory away from your veterinarian's office, so it may be a few days before you receive the test results.

In the event additional tests are needed, your veterinarian can conduct a polymerase chain reaction, or PCR, test using a diagnostic laboratory. This test is often used as a deciding factor in the event the ELISA and IFA results do not agree.

When to Test a Cat

Although there are no hard and fast age limits on testing a cat for FeLV, here are some situations in which a test might be appropriate:

  • A cat or kitten that's being adopted
  • A cat or kitten with an unknown FeLV status
  • A cat or kitten that may have been exposed to FeLV
  • A cat or kitten that is ill with an undiagnosed disease
  • A cat or kitten that is about to receive the FeLV vaccination

When to Administer the FeLV Vaccination

Once you've determined your cat's FeLV status, the next step if she tests negative is to have her vaccinated against the disease (Vaccination of FeLV-positive cats has not been shown any benefits to them).

Kittens can receive the first round of immunizations when they are between 8 and 10 weeks old, with a follow-up booster required a month later. The third round of vaccination occurs when the kitten is about a year old, with annual revaccinations after that to maintain the cat's immunity.