FIV (Feline Immunodeficiency Virus) in cats

Recognise the signs

• FIV itself is often asymptomatic for years after infection — the virus slowly weakens the immune system over time
• Recurrent infections — bacterial, fungal, parasitic — that are unusually severe or slow to resolve
• Chronic or recurrent upper respiratory infections
• Persistent gingivitis or stomatitis (mouth inflammation) — strongly associated with FIV
• Chronic diarrhoea or gastrointestinal upset
• Weight loss and poor body condition
• Enlarged lymph nodes
• Eye problems — chronic conjunctivitis, uveitis
• Neurological signs in advanced disease — behavioural changes, seizures
• Increased susceptibility to cancers (particularly lymphoma)

First aid steps

1. If your cat has just been diagnosed with FIV, take time to ask your vet all your questions — this is not an emergency situation.
2. If your FIV-positive cat shows any signs of illness — however mild — contact your vet promptly. FIV cats cannot fight infections as effectively and what might be minor in a healthy cat can escalate quickly.
3. Keep your FIV-positive cat indoors or in a secure cat-proof garden to reduce risk of infections and prevent transmission to other cats.
4. Provide a calm, low-stress home environment — chronic stress worsens immune function.
5. Ensure your cat is up to date on appropriate vaccinations (discuss with vet — killed or inactivated vaccines only, never live vaccines for FIV-positive cats).
6. Feed a high-quality, complete commercial diet — avoid raw meat, which risks bacterial and parasitic infections a compromised immune system may struggle to fight.

When it can usually wait

• A newly diagnosed but clinically healthy FIV-positive cat — schedule a comprehensive vet appointment within 1–2 weeks to establish a monitoring plan; no emergency action required

Common causes

• Transmission primarily via deep bite wounds from infected cats — the virus is present in high concentrations in saliva
• Unneutered tom cats are the main reservoir and most common transmitters through territorial fighting
• Vertical transmission (mother to kitten) is possible but less common; some kittens born to FIV-positive mothers will test transiently positive due to maternal antibodies but are not truly infected
• Sexual transmission is possible but considered a minor route compared to bite wounds
• Sharing food bowls, water, and mutual grooming between non-fighting cats represents very low risk of transmission
• Indoor cats with no contact with unknown cats are at very low risk of acquiring FIV

What the vet will need to know

• When was the cat tested, and which test was used?
• Was the positive result confirmed by a second test (e.g. Western blot) — false positives occur with ELISA snap tests, especially in recently vaccinated cats or kittens under 6 months with maternal antibodies
• Is the cat showing any current symptoms?
• Is the cat neutered?
• Is the cat indoors or outdoors?
• Are there other cats in the household?
• What is the cat's vaccination and worming history?

Aftercare

• FIV is managed, not cured. Management involves: regular vet check-ups (every 6 months for stable cats), prompt treatment of any infections, appropriate vaccination with killed vaccines only, parasite control, and a high-quality diet.
• Antiviral therapies (e.g. Interferons) are used in some cases but evidence for their efficacy is variable — discuss with your vet.
• Monitor body weight, appetite, dental health, and lymph nodes regularly.
• Neutering is essential if not already done — reduces fighting and transmission risk.
• FIV-positive cats can cohabit with FIV-negative cats if there is no fighting — the risk of transmission through social grooming and shared feeding is very low. Many UK rescue organisations now rehome FIV-positive cats into households with FIV-negative cats where there is no established fighting history. Discuss with your vet and the rescue for individual risk assessment.
• Provide indoor enrichment, stable routines, and low stress — immune function is sensitive to chronic stress in FIV-positive cats.

Prevention

• Neuter all cats — reduces territorial fighting dramatically, the primary route of transmission.
• Keep cats indoors or in a secure garden to prevent contact with unknown cats.
• Test all new cats before introducing them to a household with FIV-negative cats.
• No FIV vaccine is currently available in the UK.
• Early identification of FIV status allows earlier management — consider testing any cat with recurrent infections, chronic stomatitis, or unexplained weight loss.

Breed-specific notes

• All breeds are equally susceptible to FIV — risk is determined by lifestyle (outdoor, entire male) rather than breed.
• Free-roaming unneutered toms in areas with high stray cat density are at highest risk.
• Cats in multi-cat households with established fighting may have elevated transmission risk.

Frequently asked questions

Related topics

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