Moderate severity
Feline Immunodeficiency Virus (FIV)
Often called 'feline AIDS', FIV slowly weakens the immune system over years. With good care, however, most infected cats live long, normal lives — and the virus cannot be passed to humans.
⚠️ Common symptoms
Feline immunodeficiency virus is a lentivirus — a 'slow virus' — and a feline cousin of the human virus HIV. The comparison frightens many owners, but two facts should reassure them immediately: FIV is species-specific and cannot infect humans or other non-feline pets, and most FIV-positive cats remain healthy for the great majority of their lives. A diagnosis is the beginning of careful management, not an emergency.
The virus works by gradually targeting the immune system's white blood cells. Infection usually passes through three phases: an initial acute phase with mild, often unnoticed fever and swollen glands; a long asymptomatic phase that can last many years during which the cat seems entirely well; and, in some cats, a final phase in which immune defences become weak enough that secondary infections, chronic gum disease, and certain cancers take hold. Crucially, many cats never progress beyond the asymptomatic phase and die in old age of unrelated causes.
What sets FIV apart from FeLV is how it spreads. FIV lives in saliva but is transmitted efficiently only when that saliva is injected deep beneath the skin — that is, through serious bite wounds. The classic patient is therefore an intact tom that roams and fights. Cats that live together calmly, share bowls, and groom one another pose very little risk to each other, which is why neutered FIV-positive cats can usually share a home with negative cats without special precautions beyond keeping the peace.
Management is mostly common sense applied diligently. Keep the cat indoors to protect both its own fragile immune system and other cats in the neighbourhood; feed a complete, balanced diet and avoid raw food, which carries a higher infection risk; stay on top of dental and gum care, since stomatitis is one of the most common FIV-related problems; and treat any illness early and fully rather than waiting to see if it resolves on its own. With that level of attention, an FIV-positive cat's life expectancy can be very close to that of an uninfected cat.
🔍 Causes
FIV is transmitted almost exclusively through deep bite wounds, which is why it is most common in unneutered, free-roaming male cats that fight over territory. Unlike FeLV, it is not readily spread by sharing bowls, grooming, or casual contact, and transmission from mother to kittens is uncommon. This makes responsible cohabitation of FIV-positive and negative cats entirely feasible in a calm, neutered household.
🛡 Prevention
Neutering is the single most effective step, as it sharply reduces the fighting and roaming that spread the virus. Keep cats indoors or in a secure catio, and test new cats before introduction. There is no widely available, reliable FIV vaccine in most countries, so prevention rests on avoiding fights and exposure. Kittens born to positive mothers may carry maternal antibodies and should be retested after six months of age.
💊 Treatment
There is no cure, but FIV is very manageable. The priorities are keeping the cat indoors, feeding a complete diet, treating dental and gum disease (which is especially common), and addressing any infection quickly and thoroughly. Routine wellness checks every six months catch problems early. Importantly, FIV-positive cats can often live peacefully with non-aggressive housemates, as the virus spreads mainly by deep bite wounds.
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⚕️ Medical disclaimer
- This information is educational only and is not a substitute for veterinary advice.
- Symptoms overlap between conditions — only a vet can diagnose accurately.
- Never withhold treatment or self-medicate based on information found online.
- When in doubt, call your vet. Early intervention almost always leads to better outcomes.