Feline immunodeficiency virus (FIV) is a lentivirus that progressively impairs the immune system of infected cats, causing susceptibility to opportunistic infections. Despite its common name "feline AIDS," many FIV-positive cats live long, healthy lives with appropriate management. Understanding the disease enables owners to provide excellent welfare support.
Transmission and Prevalence
FIV is transmitted primarily through deep bite wounds — making entire male cats that roam and fight at highest risk. Casual contact (shared food bowls, mutual grooming) does not transmit FIV. Mother-to-kitten transmission is possible but uncommon. UK prevalence in outdoor cats is estimated at 5–10%. FIV is species-specific — it cannot infect humans or other non-feline species.
Disease Progression
After initial infection, cats pass through stages:
- Acute phase (weeks–months): Fever, lymphadenopathy, inappetence — mild and often undetected
- Asymptomatic phase (months–years): Cats appear healthy despite viral replication; CD4+ T-cell counts slowly decline
- Progressive phase: Declining immune function; increasing susceptibility to secondary infections, oral disease, and some cancers
Many FIV-positive cats remain in the asymptomatic phase for their entire lives and die of unrelated causes.
Clinical Presentations
- Severe, recurrent, or unusual infections (dental, respiratory, gastrointestinal, skin)
- Chronic gingivitis and stomatitis — very common in FIV-positive cats
- Weight loss and inappetence
- Neurological signs (behavioural changes, seizures)
- Increased cancer risk (lymphoma)
Management
There is no cure for FIV. Management focuses on:
- Indoor housing — protects FIV-positive cats from secondary infections and prevents transmission to other cats
- Regular veterinary monitoring (biannual examinations, annual bloodwork)
- Prompt treatment of secondary infections
- Good nutrition — complete, balanced diet supports immune function
- Dental care — regular professional cleaning under anaesthesia when needed
- Avoiding immunosuppressive drugs unless absolutely necessary
Welfare and Quality of Life
FIV-positive cats should not be euthanised solely on the basis of their diagnosis. Quality of life assessment focuses on current clinical status, not infection status. Cats in the asymptomatic phase have good quality of life indistinguishable from FIV-negative cats. Euthanasia is appropriate when secondary disease causes unmanageable suffering — the same criterion applied to any cat. Owner education about realistic prognosis is a key veterinary communication responsibility.