Q. Recently, a stray cat appeared on my porch, and he is the sweetest thing. I would like to adopt him and bring him into our house, but when I brought him to the veterinarian, he tested positive for Feline Immunodeficiency Virus (FIV). I am concerned because I have two other indoor cats. Can you provide some advice about how to proceed?
A. I think it is wonderful that you have already done so much for kitties who need homes and that you are still willing to take more cats into your family. I understand your concern about FIV, as it is a serious viral disease of cats, but it is also important to realize that cats can live with FIV for years in some cases, and that depending upon a number of factors, infected cats can be integrated into homes that already have kitties. Perhaps a brief review of how FIV infects and affects cats would be helpful.
FIV is a member of the retrovirus family, which consists of viruses that infect cells (in this case, primarily white blood cells) and use the machinery of infected cells to make copies of itself by repetitively using their genetic material (ribonucleic acid, or RNA) to make another type of genetic material called deoxyribonucleic acid (DNA). This is incorporated into the host cell DNA and is used to make copies of the virus that ultimately infect other cells.
FIV is a very common disease of cats, infecting between 2.5 and 4.5 percent of domestic cats, and it is found in relatively high concentration in the saliva of infected cats. It is transmitted primarily by deep bite wounds and (rarely) scratches. In very rare cases, FIV can be transmitted from a pregnant queen to her offspring during pregnancy, but this is not believed to be a common occurrence. This mode of transmission is very different from another common retrovirus of cats, Feline Leukemia Virus (FeLV), which can be transmitted by casual contact with the urine, saliva, nasal secretions, feces, and milk of infected cats. These different modes of infection significantly impact recommendations regarding the management of cats with each of these viral diseases.
Cats infected with FIV can remain asymptomatic for long periods of time. The median survival time of cats diagnosed with FIV is approximately five years, although many FIV-infected cats live longer than this if managed appropriately. When cats do succumb to FIV, this is often due to suppression/abnormal function of the immune system, which can predispose to infections and certain types of cancer.
An important point here is that if this kitty can be introduced into your household without any fighting between cats, the likelihood of transmitting FIV from this kitty to your other cats is low. Of course, it will be important to keep the kitties separated (even by a screen or gate) until you can be sure that they get along. You may wish to consider vaccinating your other cats against FIV prior to introducing the new kitty, and if this is the case, it will be important to test them for FIV first, as current tests cannot distinguish an FIV-infected cat from one who has been vaccinated (the test identifies antibodies that are produced both in response to vaccination and to natural infection with the virus). If you choose to vaccinate your current kitties, it would be best to keep them separated from this new guy for two months following completion of the vaccine series. Please discuss this option with your veterinarian, as he/she is in the best position to make specific recommendations regarding your situation and how to manage it.
In terms of managing this FIV-positive kitty, it would be best to take him to the veterinarian twice yearly to monitor for signs of illness and to be proactive about any problems that may arise. Making sure he is getting a nutritionally complete and balanced diet, that he is free of parasites, and that he maintains his weight are also important. Finally, it would be best to keep him indoors if you decide to adopt him, as he is a source of FIV infection for other outdoor cats, particularly if he were to get in fights with them.
I hope that this is helpful. Please visit the Cornell Feline Health Center’s website at the address below for more information on FIV, and keep us up to date on how things are going.
—Best regards, Elizabeth
Elizabeth is thankful for the assistance of Bruce G. Kornreich, DVM, Ph.D., ACVIM, Associate Director of the Cornell Feline Health Center, in providing the answer on this page.