What is FIV in Cats?


What is FIV in Cats?

Feline Immunodeficiency Virus (FIV), also known as Feline AIDS, is a serious viral disease that affects only cats. Fortunately, there are many ways we can protect our cats from exposure to this disease. It is estimated that 3.5% of cats in the western United States are infected with it.

How does FIV cause disease?

FIV causes suppression of the immune system by attacking important cells of the cat’s immune system which protect the cat from common infectious agents (bacteria, viruses, etc). Many of the infectious agents are found in the everyday environment but don’t cause disease in healthy cats. However if a cat’s immune system is weakened, as with FIV, these same organisms can cause disease — known as secondary or opportunistic infection. The disease is comparable to the human HIV but it only affects cats. However, it is recommended that immunocompromised people (i.e., chemo patients and human AIDS patients) do not reside with FIV positive cats because these cats are more likely to harbor opportunistic infections that could be transmitted to immune-compromised humans.

What is the outcome of disease?

The acute (beginning) phase of the disease is the period following initial infection. The acute phase may last days to weeks and the cat may have a fever, depression, diarrhea, vomiting, an inflamed mouth or swollen lymph nodes.  However, many owners may not notice this phase of disease. Following the acute phase, the cat usually enters an asymptomatic phase where the cat is free of signs of disease and lives a healthy life for many years. Some cats will neverdevelop into the terminal or acquired immune deficiency (AIDS) phase but some will. If the cat’s disease progresses into this AIDS phase, the immune system cannot fight off bacteria, virus, or fungi in the environment and the cat can become very ill and not recover. FIV infection is for life, but it is important to remember many cats with FIV can live a happy, healthy life for many years. FIV positive cats must be kept indoors only, have good nutrition, avoid raw diets, be provided with low stress environments and need regular visits to the veterinarian, and all cats in the household need to be fixed to reduce transmission.

How does a cat get FIV?

The most common way cats get the disease is through deep bite wounds from an infected cat. Cats who are most commonly infected with FIV are intact (not neutered) male cats that are allowed outdoors; this is because intact animals tend to roam and get into fights with other cats. On rare occasions the virus can be transmitted from mother to kittens. Sexual transmission is unusual although the semen of infected cats frequently contains the virus. Cats living together are unlikely to contract the virus from casual contact provided the cats get along and do not fight.

How do we test for it?

A simple in-house blood test can be performed to test for FIV. If the test is positive it could mean that the cat has FIV or that the cat has been vaccinated at some point in their lifetime for FIV, thus producing the antibodies that show up on the test. Kittens who test positive should always be retested, as they can be a false positive due to antibodies from their mom. A positive test should be confirmed by a Western Blot. If the test is negative, it could mean that the cat is not infected with FIV or that the cat was recently infected (up to 60 days ago) but won’t test positive yet.

Is there a vaccination?

A vaccine is available BUT it only protects against some subtypes of the virus and will cause the cat to test positive for FIV on all future blood tests. Animal shelters routinely euthanize cats who have FIV, so if a vaccinated cat was lost and turned in to a shelter, the cat will likely test positive due to the vaccination not the disease, yet still be killed. If a cat is vaccinated for FIV, it should have a microchip that is linked to information stating the cat was vaccinated for FIV.

How can we best protect our cats from contracting FIV?

  • Keep tame cats exclusively indoors
  • Spay and neuter, which reduces urge to roam and fight
  • Isolate cats and test them for FIV before allowing them to intermingle with your existing cats


Article written by Dr. Amanda Page, DVM. Published with permission. For more information, see Cornell University’s online brochure on FIV.