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MedicalDictionary.comThe Free Veterinary Medical Dictionary
Medical Condition🐈 Catshematologic immune

Feline Immunodeficiency Virus (FIV)

🗣️ Pronounced:FEE-lyne ih-myoo-noh-deh-FISH-en-see VY-rus
In One Sentence (Plain English)

A lentivirus infection of cats that gradually depletes CD4+ helper T-lymphocytes, leading to progressive immune dysfunction.

Editorial Status: Verified from peer-reviewed veterinary sources (v1.0)
Updated: 2026-01-15

💬 In Plain English

Often called "feline AIDS," Feline Immunodeficiency Virus (FIV) is a viral condition that targets and slowly weakens a cat’s immune system. Unlike FeLV, FIV is transmitted almost exclusively through deep, penetrating bite wounds during territorial cat fights (making unneutered outdoor male cats the most frequent victims). It does not spread easily through casual contact, sharing food bowls, or mutual grooming. Cats with FIV often live long, happy, completely normal lives for many years without ever developing severe immune collapse, provided they are kept indoors and receive good preventive veterinary care.

🔬 Clinical & Technical Depth

For Vets & Technicians

Formal Clinical Definition

Lentivirus infection characterized by three phases: acute phase (transient fever, lymphadenopathy), prolonged asymptomatic latent phase (lasting years), and progressive terminal immunodeficiency phase characterized by opportunistic infections, neoplasia, and wasting.

Why Veterinarians Use It

Veterinarians test for FIV antibodies using an in-clinic blood test during routine feline health assessments or when treating chronic dental disease and abscesses.

Clinical Context Encountered

Frequently diagnosed in mature outdoor male cats, newly rescued stray cats, or cats presenting with severe stomatitis.

Clinical Reference Guide (Medical Condition)

Severity
Emergency StatusNon-Emergency Care
🚨 Red Flag Warnings (When to Contact an Emergency Vet)
  • •Infections or bite wounds in an FIV-positive cat require immediate veterinary attention, as impaired cell-mediated immunity allows minor bacterial infections to progress rapidly.

❓ Questions to Ask Your Veterinarian

Take these actionable questions with you to your next clinic visit or appointment:

  • 1Did the blood test detect FIV antibodies, and is confirmatory Western blot or PCR testing needed?
  • 2Can an FIV-positive cat safely live in the same home with other spayed/neutered cats if there is no fighting?
  • 3What specific preventive care schedule (biannual exams, bloodwork, dental cleanings) is recommended?

Academic & Clinical References