Feline Immunodeficiency Virus

FIV (feline immunodeficiency virus) is in the retroviral family of lentiviruses. This class of RNA viruses functions by converting its RNA into DNA using an enzyme called reverse transcriptase and then integrating that DNA into the host’s DNA. After initial infection these viruses either integrate with the host cell and remain latent, or they integrate with the host cell and begin to rapidly replicate their own RNA. And when the host cell replicates (as cells will do) the host cell will be forced to create copies of virus RNA. In the case of FIV upon leaving the host cell the virus also kills the host cell.

FIV specifically infects the CD4+ T-cells (there are multiple types of T-cells) and macrophages which are cells that produce the cellular-mediated immune response in the body. Upon initial infection with FIV large numbers of virions are produced and subsequently large numbers of T-cells and macrophages are killed. This will produce flu-like symptoms in the cat (fever and enlarged lymph nodes). The immune system will recognize this foreign virus in the body and produce antibodies and various types of T-cells to kill the virus. After the battle the immune system will usually “have won” and only a small percentage of T-cells infected with the virus in a latent or dormant state will remain. Many cat owners do not even notice this stage of the disease as it is short lived and generally clears up on its own. At this point the cat will be asymptomatic (and can remain this way for months or years). The virus then slowly moves to other parts of the body (usually to the lymph nodes of the body) while slowly replicating itself and killing T-cells. During this time period your cat may get a few infections here and there but nothing too horrific. Each time the cat contracts a new infection T-cells will replicate to combat it, and since FIV has integrated itself into the T-cell DNA it will replicate as well. Thus the cat gets into a bit of a catch-22. The more infections the cat gets, the more T-cells are activated, which produces more virus, which kills more T-cells. As the T-cells in the body slowly diminish the cat is more and more susceptible to greater infection. Once the levels of T-cells fall below a certain point the cat is considered to have Feline AIDS. Once this occurs he/she usually falls victim to a secondary disease that the body can not fight off.

It is currently thought that FIV is only transmitted through bites as infected cats are known to shed the virus in their saliva. It is not thought that the virus can be transmitted from cat to cat by casual means (licking, sharing food, touching noses, sharing litterboxes). Although it is probably better to be safe-than-sorry and keep an FIV+ cat separated from other pets in your home. FIV, although it acts similar to HIV, is genetically and structurally different from HIV and can not be transmitted to you.

FIV is seen in cats of all ages and breeds. However, FIV is seen mostly in feral males who come in contact with many other cats and often get into fights (this makes sense as this disease is thought to have a bite as the primary mode of transmission).

Symptoms to look for:

  • Chronic skin infection
  • Chronic bladder infection
  • Chronic upper respiratory infection
  • Chronic gum disease
  • Chronic conjunctivitis
  • Any other secondary infection that doesn’t go away
  • Poor coat
  • Enlarged lymph nodes
  • Fever
  • Weight loss
  • Lethargy
  • Diarrhea
  • Neurologic Signs


The test performed to find FIV is called an ELISA (enyzme linked immunosorbent assay) test and it looks for the presence of the antibody. This test is about 90% accurate and can give false-negatives. Thus if your cat has all of the symptoms but comes back negative on the ELISA test he/she still may have FIV. You may want to ask your vet to perform a virus isolation test such as an indirect immunofluorescence antibody assay (IFA), western blotting or Immunoblotting. These are generally much more accurate. However, these tests are more costly and take longer to get results back so only request them if your cat has come up FIV- on the ELISA but you still are fairly sure he/she has FIV.

Once your cat has FIV he/she will always have the virus. There is no cure at this time. The general method of therapy at this time is to treat the secondary infections. Cats can lead a very long and full life with FIV depending on the severity of the disease and how well the cat is taken care of. A good diet, low stress, a clean home (to keep bacteria in the environment low), and drug therapy are all going to be part of keeping your cat as healthy as possible for as long as possible. Remember if your cat has FIV the largest problem faced with will be from the fact that he/she is immunocompromised (ie. the immune system isn’t as strong as it should be in warding off disease and infection). With that, try to keep your cat out of any situations in which it may get sick, and if he/she does get sick treat the infection or illness asap. Also as FIV is contagious keep your cat indoors so he/she can not infect other cats, conversely this will also benefit the FIV+ cat as he/she will have less contact with other cats with disease or illness.

In humans with HIV there are many drug therapies commonly used including anti-virals (reverse transcriptase inhibitors, protease inhibitors) and antiretrovirals (hydroxyurea). It is not completely known whether or not these types of drugs can be beneficial in felines with FIV. Many cat owners are currently using combinations of some of these drugs and are having great success with them. Some other controversial drugs that are being used for treatment of FIV include immunoregulin (stimulates the immune systems cell-mediated response) and acemannan (an aloe vera derivative which has been shown to stimulate the immune system). If your cat has FIV you should consult your vet and ask his/her opinion on what medications you can try and what might work. If your vet doesn’t seem to know as much as you would like don’t be afraid to go elsewhere to find FIV information and FIV treatment.

Precautionary measures:

Make sure your cat eats a high-quality, high-protein diet. Keep your cat out of fights and away from unknown animals. If you can, keep your cat indoors where the chance of being bitten by a FIV+ cat is slim to none. Also if you have one FIV+ cat you will need to take precautions to make sure that he/she does not come in contact with any other cats that you may have.

Click here to read John Finlow’s book about FIV treatment. This book includes medications used, sources of supply, details of treatment and results.