This email came from Nancy.
My 12 year old cat Billy was recently tested positive for FIV. He used to be free roaming. He now lives completely indoors and gets along well with my three other cats. I am going to get my other cats tested for FIV, to be on the safe side. As of right now Billy seems to be doing well, though I am keeping a vigilant eye on him. My main questions are: What is the best way to care for Billy, in terms of should I feed him anything special, do I need to make sure that he stays warm, etc? What are the warning signs that I need to look out for as the disease progresses?
Feline immunodeficiency virus is very similar to HIV in humans. Both viruses can lay dormant for years, during which time there are no outward signs of illness. FIV affects the immune cells and bone marrow, making cats more susceptible to infection. Because of a deficiency of proper immune cells the entire immune system is reduced in efficacy (hence the name). The virus itself does not cause death. Instead infections that would otherwise be fought off take hold and lead to serious illness.
As long as Billy is acting normal, there really isn't anything you can or need to do for him. Until the virus activates, there really isn't anything wrong with him and he doesn't need care any differently than a non-infected cat. The best thing you can do is to keep him inside (as you are doing) and keep stress to a minimum. Physiologic stress can lower the immune system and cause dormant viruses to become active. Being inside keeps him from spreading the virus and puts him at a lower risk for injury and disease.
You also need to have him seen regularly by your vet. I would recommend a minimum of every six months even if he is acting normal. A full chemistry panel and blood cell count may show early signs of oncoming illness and would give you some warning that something is wrong, so this should be done at least annually. Also take him in at the first sign of any illness in order to try and head it off.
If and when the virus activates, the initial symptoms will likely be subtle. You may notice a decrease in activity and appetite, find him acting more reclusive, or see some weight loss. Most of the time there aren't dramatic changes early on. If you see these things talk to your vet, as there will likely be changes in the blood cell count that will confirm that the disease is progressing. At that point there are only limited things that can be done.
Best of luck to you.