Feline Immunodeficiency Virus (FIV)

Feline immunodeficiency virus (FIV) causes immunosuppression and can hinder a cat’s ability to protect itself against infections.

The disease has three major phases: acute viremia, asymptomatic, and a positive or negative progressive dysfunction of the immune system.

Typically, the cat is asymptomatic during the first phase, which can include a transient fever and lymphadenopathy. This stage often goes unnoticed by cat owners. After the acute phase, cats enter a prolonged asymptomatic phase that eventually result in two outcomes: maintenance of the disease for the duration of the cat’s life or dysfunction of the immune system.  
Feline Heartworm
Diagnosis
Treatment

The American Association of Feline Practitioners (AFP) recommends testing all at-risk cats, sick cats and kittens to determine infection status. Antibody ELISA is the most common method for FIV testing. It detects FIV antibodies in the blood stream as early as 60 days post-exposure. The Western Blot test detects antibodies in the blood using a slightly different technology. The Western Blot is considered the confirmatory test for FIV.

Adult cats (>6 months of age)—FIV diagnostic algorithm

View/print the algorithm, part of the Diagnosing and Managing Patients with FIV/FeLV guide. (PDF)

FIV Diagnostic Algorithm

Kitten (>6 months of age)—FIV diagnostic algorithm

The testing algorithm for kittens is slightly different because maternal antibodies can persist in the kitten for up to six months.

View/print the algorithm, part of the Diagnosing and Managing Patients with FIV/FeLV guide. (PDF)

FIV Kitten Algorithm

Vaccinated Cat

Antibodies produced as a result of vaccination with the killed, whole virus vaccine are indistinguishable from those produced as a result of natural infection. Vaccinal antibodies may persist for a year or longer and interfere with the diagnosis of FIV by serology. If a cat is antibody positive, as confirmed by a second serologic test, and its vaccination history is in question, or if a cat has been vaccinated for FIV but infection is still suspected, then additional testing by the PCR methodology may help determine if the cat is infected. A positive FIV RealPCR test result confirms that the cat is infected with FIV, but a negative PCR result, however, does not rule out infection. FIV PCR testing is not recommended as an initial screening diagnostic for FIV.

FIV Diagnostic Testing Algorithm AAFP Guidelines with PCR

View/print the algorithm. (PDF)

FIV with PCR Algorithm