What is Feline Immunodeficiency Virus (FIV)?
The Feline Immunodeficiency Virus (FIV) is likened to the AIDS virus in humans because of their similarities. Fortunately, most viruses are species specific. This is the case with the human AIDS virus and with FIV. The AIDS virus affects only humans and FIV affects only cats.
Which cats are likely to be infected with FIV?
FIV is transmitted primarily through bite wounds that occur in cat fights. Other interactions, such as sharing common food and water bowls or grooming, have not been shown to be significant in transmission.
What are the clinical signs?
An infected cat will generally go through a prolonged period of viral dormancy before he/she becomes ill. This incubation period may last as long as six years; therefore, we generally do not diagnose FIV in sick cats that are relatively young.
When illness occurs, the cat may experience a variety of severe, chronic issues. The most common illness is a severe infection affecting the gums around the teeth. Abscesses from fight wounds, which would normally heal within a week or two may remain active for several months. Respiratory infections may linger for weeks.  The cat may lose weight or go through periods of not eating well and the hair coat may become unkempt. The cat may also have episodes of treatment-resistant diarrhea. Ultimately, widespread organ failure can occur.
How is FIV diagnosed?
Evidence of exposure to FIV can be detected by a simple blood test. A positive test means the cat has been infected with the virus and will likely remain infected for the remainder of his/her life. A negative test may mean that the cat has not been exposed; however, false negatives do occur.
FIV Testing in Adult Cats
It may take up to three months after the initial infection for an FIV test to turn positive. This means that, for up to three months, the test may be negative even though the virus is present in the cat.
Rarely, the test may also turn negative when a cat becomes terminally ill with FIV. This occurs because antibodies (immune proteins) produced against the virus become attached and bound to the large amount of virus present. Since the test detects antibodies that are free in circulation, the test may be falsely negative.
FIV Testing in Kittens
The vast majority of kittens under four months of age that test positive for FIV have not been exposed to the virus. Instead, the test is detecting the antibodies that were passed from the mother to the kitten. These antibodies may persist until the kitten is about six months old; therefore, the kitten should be retested at that time. If the test remains positive, the possibility of true infection is much greater. If the kitten tests negative, there is no cause for worry.
If an FIV-infected cat bites a kitten, he/she can develop a true infection. However, the FIV test will usually not turn positive for several months. If a mother cat is infected with FIV at the time she is pregnant or nursing, she can pass large quantities of the virus to her kittens. This means of transmission may result in a positive test result in just a few weeks.
Is treatment possible?
While there is no cure for FIV, the disease state can sometimes be treated with antibiotics or other drugs to stimulate the immune system, restoring the cat to relatively good health. However, the virus may become active at a later date.
If you have a cat that tests FIV-positive but is not ill, it is not necessary to immediately euthanize him/her.  As long as the cat does not fight with other household cats or those of your neighbors, transmission is not likely to occur. However, if the cat is prone to fight or if another cat often instigates fights with him/her, transmission is likely. In fairness to your neighbors, it is generally recommended to restrict an FIV-positive cat to the house. Owners of infected cats must be responsible so the likelihood of transmission to someone else's cat is minimized.
Can this virus be transmitted to me or my family?
The feline immunodeficiency virus is cat-specific. It does not infect humans.
How can I prevent my other cats from getting infected with FIV?
Neutering male cats and keeping an infected cat indoors are the only available preventive measures for this virus. Currently, no vaccine is available to prevent infection.