Feline Immunodeficiency Virus (FIV), also known as feline AIDS, is a lentivirus belonging to the family retrovirus that affects domestic cats worldwide. FIV was first identified in 1986 and causes chronic immunosuppression, which makes the affected cats susceptible to opportunistic secondary infections, neoplasia, and inflammation.

FIV is closest to the human immunodeficiency virus (HIV), but it is harmless in individuals and other animals. The progression of FIV varies widely from asymptomatic carriers to highly immunocompromised felines.

Some FIV-positive cats live relatively well for years. Yet, disease progression will ultimately result in chronic systemic decline if left untreated and in the absence of care and monitoring.

FIV has three distinct clinical phases:

• Acute phase: clinical symptoms include mild fever and lymphadenopathy.
• Asymptomatic phase: may last for months to years.
• Terminal stage: extreme immunodeficiency and heightened risk for opportunistic infection.

FIV is not curable, and the use of vaccines is in dispute due to diminished effectiveness and interference with diagnostic workup. Supportive care, confirmatory diagnosis, and rigid infection control are the foundations of FIV therapy in the veterinary clinic.

How It Spreads

FIV transmission is most often due to deep bite wounds, and therefore fighting between intact male free-roaming cats is the most frequent mode of transmission. Saliva is the primary fluid carrying infectious viral particles.

Other transmission routes include:

Vertical transmission from queen to kitten (rare but possible)

• Blood transfusions from positive donors
• Close, intimate contact transference in high-density environments, although ineffective and rare
• Litter boxes, food dishes, or casual grooming are not the reasons for FIV transmission.

Who Is at Greater Risk

Cats at the most significant risk are:

• Unneutered males
• Outdoor, free-roaming cats
• Cats living in feral colonies or shelters
• Cats with a bite wound history
• Middle-aged to older cats, with infection occurring at any age

FIV prevalence varies geographically but is higher in areas with high feral cat populations and low neutering rates.

How Do Cats Get FIV

Following a cat bite wound from an infected animal, the virus enters the bloodstream and infects lymphocytes, particularly CD4+ T-helper cells. The immune system may keep the virus under control temporarily, but fails to eradicate it entirely.

Rather, the virus integrates into the host genome for a chronic, lifelong infection. As the immune function further decreases, secondary bacterial, viral, fungal, and parasitic infections, immune-mediated illness, and certain neoplasms are more likely to occur in cats.