CONDITION

Feline Immunodeficiency Virus (FIV)

Why this matters now

Feline immunodeficiency virus is a lentivirus that affects cats worldwide. Infection is most common in outdoor, unneutered male cats due to transmission through bite wounds during fighting. Once infected, cats carry the virus for life. However, many FIV-positive cats live for years with good quality of life, and the diagnosis often carries more anxiety than the actual disease warrants.

After initial infection, cats may experience a brief period of mild illness including fever and lymph node enlargement. This is followed by a prolonged asymptomatic phase that can last many years—often the entire lifespan of the cat. Some infected cats eventually develop acquired immunodeficiency, making them more susceptible to secondary infections, but this progression is variable and often slow.

Signals & patterns

Early signals

Often no visible signs

Most cats show no signs during the long asymptomatic carrier phase.

Mild, self-limiting illness after initial infection

Some cats experience transient fever and lymph node swelling shortly after becoming infected.

History of bite wounds

Cats that have been bitten during fights may have been exposed to the virus.

Discovery on routine screening

FIV is often diagnosed incidentally when testing new cats or during health checks.

Later signals

Recurrent infections

Cats with progressed FIV may develop recurring respiratory, skin, or oral infections.

Chronic oral disease

Gingivitis and stomatitis can be more severe in immunocompromised cats.

Weight loss

Gradual weight loss may occur as the disease progresses.

Persistent lymph node enlargement

Chronically enlarged lymph nodes can indicate ongoing immune stimulation.

Click to read about the biological mechanisms

How this is usually investigated

Diagnosis involves testing for antibodies against the virus, with confirmation testing for positive results. Additional assessment helps establish overall health status.

Point-of-care antibody test

Purpose: To screen for FIV infection using a small blood sample
Considerations: Rapid tests detect antibodies rather than the virus itself. Positive results warrant confirmation. Kittens may have maternal antibodies giving false positives until around six months of age.

Confirmatory testing

Purpose: To verify positive screening results using different methodology
Considerations: Western blot or PCR testing may be recommended. False positives can occur on screening tests, making confirmation valuable.

Complete blood count

Purpose: To assess red and white blood cell numbers and look for abnormalities
Considerations: Changes may indicate immune effects. Normal results are common in asymptomatic carriers.

Biochemistry panel

Purpose: To evaluate organ function and overall metabolic health
Considerations: Establishes baseline values for monitoring over time.

Assessment for concurrent infections

Purpose: To check for feline leukaemia virus and other conditions
Considerations: Co-infection with FeLV significantly affects prognosis. Testing for both viruses is routine.

Options & trade-offs

Management focuses on maintaining health and preventing secondary problems. With appropriate care, many FIV-positive cats live normal lifespans.

Indoor-only lifestyle

Keeping infected cats indoors to prevent exposure to pathogens and transmission to other cats.

Trade-offs: Reduces infection risk and prevents spread. Some cats adapt readily whilst others may find the transition challenging.

Regular health monitoring

More frequent veterinary check-ups to detect problems early.

Trade-offs: Allows early intervention for emerging issues. Frequency depends on individual circumstances.

Prompt treatment of secondary infections

Addressing any infections or illnesses promptly before they become severe.

Trade-offs: Infections may take longer to resolve and sometimes require extended treatment.

Good nutrition and parasite control

Maintaining overall health through balanced diet and prevention of parasitic disease.

Trade-offs: Supports immune function. Indoor cats typically have lower parasite exposure.

Household management

Considering whether FIV-positive cats can live with uninfected cats.

Trade-offs: Transmission risk between cats that do not fight is low. Stable households with no aggression may safely house positive and negative cats together.

Common misconceptions

Misconception:

"FIV-positive cats will become sick and die soon"

Reality:

Many FIV-positive cats live for years with excellent quality of life. The virus progresses slowly, and some cats never develop clinical disease related to their infection.

Misconception:

"FIV can spread to humans or dogs"

Reality:

FIV is species-specific and poses no risk to humans, dogs, or other non-feline species. It is not related to HIV despite some biological similarities.

Misconception:

"FIV-positive cats must live alone"

Reality:

In stable, non-aggressive households, the risk of transmission between cats is low. Cats that do not fight can often cohabit safely.

Understanding that FIV is a manageable chronic condition helps put the diagnosis in perspective. Monitoring weight, appetite, and general demeanour provides ongoing insight into health status. Noting any signs of infection—sneezing, mouth discomfort, skin problems—allows prompt attention. Creating a stimulating indoor environment helps cats adjust to lifestyle changes.

Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS