Feline Immunodeficiency (FIV) and Feline AIDS

PetMD Editorial
October 30, 2008
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Reviewed and updated for accuracy on July 9, 2019, by Dr. Natalie Stilwell, DVM, MS, PhD

Feline immunodeficiency virus (FIV) is a complex retrovirus that’s similar to HIV. And similar to the way HIV can lead to AIDS, FIV can cause immunodeficiency disease in domestic cats.

Immunodeficiency is the medical term that describes the body’s inability to develop a normal immune response. Here’s everything you need to know about FIV—the symptoms, outlook and how you can help an FIV-positive cat lead a long life.

Do FIV-Positive Cats Always Show Symptoms?

Retroviruses insert copies of their genetic material into the cat’s DNA, which means they are infected for life and cannot clear the virus from their body.

But FIV is slow-moving and may take months or years to incubate, so the virus typically lies dormant in the body before causing symptoms. Cats who are infected with FIV may not show symptoms for several years and often have a normal life expectancy.

However, they are prone to developing secondary infections and even certain types of cancer, especially during the advanced stages of the disease.

Symptoms of Feline Immunodeficiency Virus

Symptoms usually occur due to the body’s decreased ability to develop a normal immune response against infections. They may include:

  • Recurrent minor illnesses, especially with upper respiratory and gastrointestinal signs

  • Mild to moderately enlarged lymph nodes

  • Inflammation of the gums and oral tissues

  • Upper respiratory tract disease—including inflammation of the nose and eyelid tissues

  • Eye disease—including inflammation of the cornea and iris, and glaucoma

  • Long-term (chronic) kidney insufficiency and disease

  • Persistent diarrhea

  • Long-term, nonresponsive or recurrent infections of the external ear and skin resulting from bacterial or fungal infections

  • Fever, weight loss and weakness, especially in advanced stages of FIV disease

  • Cancer—particularly lymphoma, which is a cancer of the white blood cells formed in lymphoid tissues throughout the body

  • Nervous system abnormalities—including abnormal sleep pattern, behavioral changes (such as pacing and aggression) and changes in vision and hearing 

FIV Causes and Risk Factors

FIV transmission requires close contact because it is passed from cat to cat via infected saliva.

Bite wounds and scratches are the most common method of infection; less commonly, the virus can be passed from a pregnant female to her kittens. Sexual transmission is rare, although studies have detected the FIV virus in semen.

Because FIV spreads directly from cat to cat through the saliva, infection is most likely to occur in outdoor, intact males, as they are more likely to fight and roam. Indoor cats generally have an extremely low risk of contracting FIV.

There is no genetic susceptibility for infection, although genetics may play a role in how quickly the disease progresses.

How Is FIV Diagnosed?

The average age of cats when diagnosed with FIV is 5 years old, and the likelihood of infection increases with age.

If FIV infection is suspected, your veterinarian will want to perform a thorough physical exam on your cat, taking into account the background history of symptoms and possible incidents that might have precipitated this condition.

The next step is to test for FIV using an enzyme-linked immunosorbent assay (ELISA). This type of test (also known as a SNAP test) can be performed in the veterinary clinic, and works by screening for FIV-specific antibodies circulating in the blood.

Your veterinarian will need to confirm a positive test result by sending a blood sample to a commercial laboratory for a different test that’s known as a Western blot.

If your cat is confirmed to be FIV-positive, your veterinarian will assess his overall health by performing blood work and a full diagnostic workup. Blood tests typically include a complete blood count (CBC) and a serum biochemical profile.

A urinalysis will also be performed to assess kidney function and screen for urinary infections.

Your doctor may want to perform other diagnostics, including X-rays, an ultrasound or a fecal exam. This is done to rule out other health issues, including bacterial, viral, fungal and parasitic infections, as well as cancer.

Treatment for FIV Cats

Because FIV-infected cats can live for years with no symptoms, treatment may not be necessary until signs suggest that the disease is progressing.

Secondary infections are common in the advanced stages of FIV infection due to the progressive weakening of the immune system. Issues can vary from mild to serious and will be treated on a case-by-case basis.

Certain issues that can occur with advanced FIV, such as dental infections and tumor development, may need to be managed with surgery. Cats with severe dental disease may require full-mouth extractions (removal of all of the teeth) in order to alleviate the pain caused by gingivitis and other oral issues.

Your veterinarian may also recommend a special dietary plan to manage your cat’s specific health issues.

Long-Term Management and Life Expectancy

Cats with FIV infection need to be monitored by you at home and through regular visits to your veterinarian. This will help detect the development of secondary infections and other manifestations of the disease.

Progressive health issues, such as gradual weight loss and increasingly frequent secondary infections, may be signs that the FIV infection is starting to affect your pet’s quality of life.

In general, however, the earlier that FIV is detected, the better your cat’s chances are for living a long and relatively healthy life.

A nationwide study in Canada found that, while around 20 percent of cats died within 4.5-6 years after becoming infected with FIV, over 50 percent still had no signs of disease at that time. However, once progressive signs of FIV disease become obvious, life expectancy decreases to less than 1 year.

Can You Protect Cats From FIV?

Until recently, an FIV vaccine was available in North America. However, the vaccine has been pulled from the market because it caused false-positive test results and only protected against some FIV strains.

This means that managing your cat’s lifestyle is the main way to minimize risk of FIV infection. This includes spaying and neutering your cats as well as keeping them indoors to prevent contact with stray cats, who have an increased risk of being FIV-positive.

Any new cats that come into your household should be tested for FIV. If a cat tests positive, it does not mean that you can’t bring your new cat into your home. The risk of an FIV-positive cat passing the disease to other indoor cats is considered to be very low.

Recent evidence suggests that FIV rarely spreads between indoor cats who are housed together, even through grooming and sharing of food and water bowls.

An FIV-positive result will mean that your cat will need to live an indoor-only lifestyle to avoid getting into fights with other cats and spreading the disease further.

Remember that cats with FIV can live long and healthy lives, and euthanasia is not usually called for when a cat is diagnosed with FIV.

Featured Image: iStock.com/MonikaBatich