Veterinarian-written / veterinarian-approved articles for your cat.

Feline Immunodeficiency Virus

How do cats get it? How is it spread?

cat_collar_layingThe FIV is in the same Retroviridae family as Feline Leukemia Virus (FeLV), although its subfamily, the lentivirus, is different. Lentiviruses are responsible for disease in many types of animals, including acquired immunodeficiency syndrome (AIDS) in human beings, caused by HIV. FIV is often referred to as “Feline Aids.” The viruses are apparently specific for each species, and there is no evidence that FIV is infecting people, or HIV infecting cats. FIV-infected cats are found throughout the world. According to the Cornell Feline Health Center “In the United States, approximately 1-3% of healthy cats are infected with FIV.”

The primary mode of transmission of FIV is through bite wounds. Therefore outdoor cats, especially territorial tomcats, are at greatest risk of infections. Casual contact among cats sharing food and water dishes is not a significant mode of transmission as it is with FeLV. Unlike humans, sexual contact is probably not a significant way for the disease to be transmitted. This virus may be transmitted from a mother cat to her kitten, though this is rare. Kittens may also be aborted or stillborn if the mother is infected.

What happens if cats get it?

After infection, the virus enters the bloodstream (viremia) and from there it can become latent (or inactive) in the body for a while, or progress to an active disease, which eventually progresses to a terminal illness. In young kittens in the early phase of infection, fever and swollen glands (lymph nodes) may be the first signs noted. The primary target of the virus is the cells of the immune system such as CD4+ / CD8+ T lymphocytes, B lymphocytes and macrophages.

Malfunction of the body's protection system leads to many opportunistic infections. FIV infection has been associated with a wide variety of disorders including, but not limited to: enlarged lymph nodes, ulcers of the tongue and inflamed gums, progressive weight loss and wasting, poor haircoat and skin disease, diarrhea, anemia, eye and nervous disease, cancer, and many other diseases. They all take advantage of the immune system dysfunction.

Infected cats may appear normal for months to years until signs of their suppressed immune system begin to show. In the late stages, changes in behavior such as increased aggression or anxiety may occur in some cats.

How can infection be prevented?

Preventing infection is the key. Cats bitten by infected cats are at highest risk. Keeping your cat indoors alone or with tested negative cats will prevent the type of contact necessary for infection. If you introduce a new cat to the home, an FIV test should be carried out in order to make sure that the new cat is FIV negative BEFORE it is introduced to the resident cats.

A vaccine for FIV is available, but does not prevent infection in all vaccinated cats (60-80% effective after 3 doses). After vaccination the results of certain diagnostic tests may be affected, so discuss whether FIV vaccination is appropriate for your cat. Your veterinarian will help determine the risk for infection.

How is it diagnosed?

In FIV testing, confirming a positive antibody test result is crucial especially in asymptomatic cats since a portion of uninfected cats may have false positive results. A second test using a different technique will be done in the laboratory to try to confirm the positive first test. In most cases, a negative second result is reliable and means the cat is not infected. If there is discrepancy between tests, then the cat will be retested in about 12 weeks.

If the cat has been bitten by either an FIV-infected cat or a cat that has not been tested negative, starting at 60 days post-injury, testing will be done in order to pick up possible new infection.

Young kittens may have positive test results for 3 to 4 months after birth without actually being infected with the virus because of antibodies that were transferred from the vaccinated mother; others might have been born to an infected mother who passed protective antibodies to the offspring. If kittens aged 6 months or less test positive for FIV, retesting will be recommended to determine whether the kitten is positive for antibodies because they are truly infected, or whether the kitten had maternal antibodies for a while and has become negative.

False negative tests occur, though rarely. This can happen when a late stage cat is tested and the immune system is so exhausted, antibodies are no longer being produced at detectable levels.

Is it treatable?

There is no cure for FIV infection. Although the disease is considered fatal, many cats infected with these viruses but without clinical signs of disease can live for many years in relatively good health. Once infections move in, medications can be given to control those secondary diseases. Because of the immune system suppression, longer and more aggressive treatment may be needed to help FIV positive cats overcome routine infections. Some of the same drugs used in people have been tried off-label in cats and show some promise.

Identification of infected cats via testing allows the veterinarian to develop a long term management plan for cats that are positive. Once a veterinarian suspects that a cat may be infected, a quick blood sample will be taken. The test can be performed in most veterinary offices and results are usually available within ten minutes. A combination test for both FeLV and FIV is available in most facilities.

There are no medications or therapies proven to help prevent the transition from asymptomatic to symptomatic cat. Raw uncooked foods should be avoided in infected cats due to an increased susceptibility to food-born bacteria. The environment should be kept clean. If you cat dies and a new cat is coming home, complete a careful cleaning process before bringing home the new cat.

Infected cats need to see the veterinarian more frequently than a well cat. Thorough physical examination, complete blood count, blood chemistry, urinalysis, and fecal examination should be performed as recommended by your veterinarian. Symptomatic cats should receive veterinary attention promptly at the onset of any clinical signs. Accurate identification of any secondary illness is extremely important for successful treatment. Vaccination programs to prevent infection by other diseases should be maintained in asymptomatic cats. Sexually intact males and females should be altered (neutered) to reduce the stress associated with estrus and mating behaviors.

If owners are unable to quarantine infected cats from healthy cats in the home due to living circumstances, confine the infected cat indoors, or bear the costs of the veterinary care that ill cats require, the veterinarian should be consulted.

Disclaimer: This website is not intended to replace professional consultation, diagnosis, or treatment by a licensed veterinarian. If you require any veterinary related advice, contact your veterinarian promptly. Information at is exclusively of a general reference nature. Do not disregard veterinary advice or delay treatment as a result of accessing information at this site.