Diagnosing FIV in Cats
Dog Breeds
Infection by the feline immunodeficiency virus can be diagnosed using tests that identify antibodies in the cat’s blood caused by previous exposure to the virus.
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Introduction
Infection by the feline immunodeficiency virus can be diagnosed using tests that identify antibodies in the cat’s blood caused by previous exposure to the virus. Most of these tests can be performed at a local veterinary clinic, although some samples may need to be sent to an outside laboratory.
How FIV Infection is Diagnosed
Most veterinarians will perform a thorough physical examination and conduct routine blood work (complete blood count and serum biochemistry profile) on any cat presenting with nonspecific signs of illness. Currently, the screening test of choice for FIV infection is an enzyme-linked immunosorbent assay (ELISA test), which can detect antibodies against the virus in a cat’s saliva or serum, if it has been exposed to the virus. The ELISA test can have false-positive results, such as when the cat has been vaccinated against FIV. There presently is no test that can differentiate between antibodies produced by exposure to FIV (true infection) and antibodies produced in response to a vaccine. False-positive results can also occur in young kittens that still have circulating maternal anti-FIV antibodies derived from colostrum, and occasionally due to laboratory error. Accordingly, positive results from the ELISA screening test should be confirmed by either a Western Blot or a polymerase chain reaction (PCR) follow-up test, before a definitive diagnosis is made. The Western Blot confirmatory test is favored in cats known not to have been vaccinated against FIV, while the PCR test is preferred in cats that have been given the vaccine. Both of these tests are performed at a referral laboratory.
It can take several months for detectable levels of anti-FIV antibodies to form in the blood of infected cats. Kittens and cats with unknown vaccination histories should be tested at least twice – on two separate occasions after 6 months of age. All cats in a multi-cat household should be tested for FIV infection, and any new cats entering a multi-cat environment should be tested as well. Cats that are in a high-risk group, such as outdoor intact males or cats prone to fighting with others, should be tested for FIV at least annually. False negative ELISA results can occur very early in the course of infection, as well as in the end-stage of disease when levels of circulating anti-FIV antibodies are undetectable due to chronic immunosuppression.
Special Notes
Most cases of FIV infection are diagnosed incidentally during a visit to the veterinarian for some unrelated condition.
Treatment Options
Symptoms and Types