Feline Immunodeficiency Virus

Feline Immunodeficiency Virus, immunodeficiency virus (FIV) attacks a cat’s immune system, leaving it vulnerable to other infections. FIV is spread from cat to cat, primarily by biting. Shortly after becoming infected, a cat may have a fever or enlarged lymph nodes, but these signs typically go away and may not return for months or years. Weight loss is common in cats with FIV, often resulting in severe wasting late in the disease process.

Risk Factors

Cats who are allowed to roam outdoors or indoor cats who come into contact with cats who roam outdoors.


Most cats with FIV show no clinical signs. Those that do exhibit signs, may display:

  • Fever
  • Weight loss
  • Enlarged lymph nodes
  • Disheveled coat
  • Swollen or inflamed gums
  • Inflammation of the eyes
  • Pneumonia
  • Seizures
  • Frequent infections of the skin, mouth, or urinary tract


Infection with FIV is diagnosed by a complete medical history and physical examination combined with a blood test to look for antibodies to the virus.

Cats who have been vaccinated against FIV will test positive for FIV, so it’s important to let your veterinarian know if your cat has been vaccinated because testing cannot differentiate between vaccination and infection.


There is no cure for FIV, but it is rarely fatal and can be managed. Treatment depends on the cat’s signs but may include frequent dental cleaning, giving antibiotics for bacterial infections, and removing tumors.


Cat bites are the primary means by which FIV infection is transmitted, so keeping cats indoors, and away from potentially infected cats, reduces their likelihood of contracting FIV.

Until 2017, an FIV vaccination was available in the United States , but it was discontinued due to concerns over its effectiveness and its tendency to cause to false-positive test results.

By The Animal Medical Center