Feline Immunodeficiency Virus (FIV) in Cats

Feline immunodeficiency virus (FIV) is considered a lentivirus, which is a slow moving virus that is a part of the retrovirus family. Retroviruses are species specific. FIV is in the same family as human immunodeficiency virus (HIV), which is the cause of AIDS. Because both FIV and HIV are retroviruses, thus only felines can contract FIV and only humans can contract HIV. However, felines tend to weather FIV better than humans weather HIV. In fact, 90% of cats will go on to live out their normal lifespan.

This feline virus was first discovered in a California cattery in 1986 when some of the felines were exhibiting the same symptoms humans do with HIV. This doesn't mean that FIV is a new virus. In fact, there is evidence that it has been around long before it was actually discovered.

FIV is toxic to the cat's T helper cells (CD4) which is a type of white blood cell that is crucial to the immune system. FIV dramatically affects these white blood cells of the immune system by significantly damaging or even killing them. This is what causes the feline's immune system to gradually weaken. Because the immune system is responsible for fighting off disease and cancerous cells, the feline will be more prone to illnesses, disease, bacteria, and other organisms such as Haemobartonella felis (a bacteria based parasite) and Toxoplasma gondii (a parasitic protozoa).

Signs of FIV

There are three stages to the Feline immunodeficiency virus. Keep in mind that according to veterinarian researchers, there aren't any exact clinical signs that are FIV- specific no matter what the stage. This just means that the signs and symptoms could be signs and symptoms for other illnesses as well. The only way to know for certain is to have your cat tested for FIV.

Stage One

In approximately four to six weeks after a feline has been infected, some cats will have swollen lymph nodes and their white blood cell count will decline. Some cats will also have a fever, diarrhea, loss of appetite, anemia, lethargy, and neutropenia in this early stage of FIV. During this stage, the CD4 count progressively decreases thus the risk to the cat becoming ill from another disease or illness increases. Stage one can last for days, weeks, and even months and is usually undetected.

Stage Two

In stage two, the feline is asymptomatic thus showing no signs of being infected. This stage, however, can last for years.

Stage Three

This stage has been referred to as AIDS-related complex (ARC). This is due to the cat's immune system weakening significantly. The cat will become more susceptible to disease caused by bacteria, fungi, viruses, and protozoans that usually do not have any effect on healthy felines. These are considered opportunistic infections. Opportunistic infections are the main cause of death in FIV-positive felines. These infections can attack a variety of places and functions with the feline.

Immunologically the feline can suffer from anemia (persistent of recurrent low red blood cell count), leukopenia (reduction in number of circulating white blood cells), lymph node hypoplasia (decreased tissue in the lymph nodes, which impairs immune function), lymph adenopathy (enlarged lymph nodes), lymphosarcoma (cancer in lymphoid tissue).

Gastrointestinally the feline can suffer from chronic diarrhea caused by overgrowth of normal bacteria and fungi, and parasitic infections thus leading to progressive weightloss.

Neurologically the feline can suffer from behavioral changes, facial twitching, seizures, dementia, peripheral neuropathies and psychomotor abnormalities.

Dermatologically the feline can suffer from Pustular dermatitis (inflammation and visible collections of pus within the skin), chronic abscesses, chronic gingivitis (infection and inflammation of the gums), chronic stomatitis (infection and inflammation of the mucous membranes in the mouth), periodontitis (inflammation of tissues surrounding a tooth).

Ocularly the feline can suffer from conjunctivitis (inflammation of membrane lining the eyelid), keratitis (inflammation of the cornea), cataracts (partial or complete thickening of the lens), and glaucoma (increased pressure within the eye causing visual defects and possible blindness).

Reproductively the feline may have spontaneous abortions and stillbirths.

Regarding the feline's upper respiratory tract, they could suffer from chronic rhinitis which is post nasal drip or basically a runny nose.

Diagnosis of FIV

Your veterinarian can diagnose the feline immunodeficiency virus by using a blood test to detect antibodies against the virus. In most cases, veterinarians will only test for FIV if there are unexplained chronic symptoms of disease in one or more the feline's major body systems. However, the American Association of Feline Practitioners suggests that before introducing a new cat to a multi-cat household, the owner should have the cat tested for FIV. This helps in the prevention of exposing the existing cats to the feline immunodeficiency virus. The reasoning behind this is that kittens under six months of age may have the antibodies of FIV contracted from their mother without having the virus themselves. If a kitten that has been tested positive for FIV, it should be tested again after six months of age.

How FIV Is Transmitted

Feline immunodeficiency virus is present in the saliva, blood, and cerebrospinal fluid of infected felines. The virus itself is very fragile and does not survive long outside the feline's body. This is why the main source of transmission from one cat to another is through a bite wound during a fight with another cat. It is extremely rare that FIV is transmitted through casual contact with another feline. Be aware that mother cats can pass FIV to their unborn kittens.

According to Cornell University's College of Veterinary Medicine, this occurs when the kitten is being passed through the birth canal. It can also occur when kittens ingest infested milk. Sexual contact, ironically, is not high on the list for transmission. On rare occasion, it has also been known to be transmitted through a blood transfusion of blood tainted with FIV. This isn't a common occurrence though.

Risk Factors

Some of the risk factors for contracting the feline immunodeficiency virus include age, gender, illness, and the time the cat spends outdoors. Cats older than five years old are at a greater risk for contracting the virus. Male cats are more apt to fight with other cats, especially if they aren't neutered. This causes a greater risk to a male cat contracting and spreading the virus. The virus isn't as prevalent with indoor cats. Outdoor cats and feral cats come in more contact with other felines. This puts them at a higher risk for contracting the virus. Cats that already suffer from illnesses, such as the feline leukemia virus (FeLV), are also at a greater risk for contracting FIV.


Unlike HIV, there is no treatment available to specifically treat the feline immunodeficiency virus. Also, there is no known cure for FIV just like with HIV. Most treatments are targeted toward other illnesses and diseases instead of FIV itself.


There is some hope in preventing the transmission and spread FIV. Dr. Janet K. Yamamoto, a co-founder of FIV, developed a vaccine which was made available to the United States in July of 2002 for FIV. Fel-O-Vax FIV, the name of the vaccine, was licensed by the University of Florida to Kansas-based Fort Dodge Animal Health which is a division of a New Jersey pharmaceutical company.

Fel-O-Vax FIV is an ongoing vaccine. It is suggested that the first vaccine can be given to healthy kittens as young as eight weeks old. After the first initial dose, the second and third vaccination dose should be given two to three weeks later. It is advised to continue this preventative measure by giving the feline a dose of Fel-O-Vax FIV annually. However, you should know that the current FIV test cannot distinguish between the FIV antibodies and the antibodies in the vaccine. Researchers are currently working on developing better testing systems.

Although a vaccine is available, this doesn't mean that the vaccination is completely fail-safe. It has a success rate of 84% - 90%. Therefore, as a responsible pet owner, there are other ways you can help in preventing the spread of FIV. If you normally allow your cat to go outside for extended periods of time, it is time you brought your cat inside to stay. Exposure to other cats that are not in the household places your cat at high risk. Also, as I said before, if you plan to have a new addition to a multi-cat household have the new cat tested first. Cats are more likely to be aggressive if they aren't spayed or neutered, so please spay or neuter your cat.

Feline immunodeficiency virus is manageable for the most part. Also understand that the rate of infection is 1% in healthy cats to 14% in cats that are already ill. As with any disease, you should do as much research as possible. Knowledge is crucial in knowing how to give your cat the best life possible.

Other Helpful Articles on FIV and Cat Health

© 2014 Linda Soaring Eagle Sarhan

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TeriSilver profile image

TeriSilver 2 years ago from The Buckeye State

Excellent and informational, says this cat-mama. Thank you.

marcus morgan 23 months ago

My cat has been acting funny and I heard of the immunodeficiency virus. But I didn't know what the symptoms were. According to this the only way to know for sure if my cat has it is to take it into the vet to get it tested which is good to know.

Snakesmum profile image

Snakesmum 16 months ago from Victoria, Australia

Well written hub, which covers everything one needs to know about FIV. Having had cats with this in the past, I'm all too familiar with it! Voted up.

AnneRako profile image

AnneRako 14 months ago from Chicago

Fantastic article! I think I might link to this from my hub if you don't mind since yours provides more practical FIV information.

LindaSarhan profile image

LindaSarhan 14 months ago Author

Anne, that is more than okay. Thanks! I have also added your article link to this article. It is a good compliment to the article.

LaurieNunley517 profile image

LaurieNunley517 9 months ago from Deep South

Very helpful and informative article!

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