I have a mixed household of FIV and none Fivers. I treat them all equally and my vet says just to keep a special eye on the Fivers, as any infection could be serious to their health. There is no reason for FIV positive cats to be restricted from free movement unless they are known fighters, or unneutered, as deep bites and mating are the two ways in which FIV is spread. It cannot be spread by sharing food or water, or mutual grooming, it cannot be spread by sneezes or scratches, so the chances of your 14 year old being any risk to the cat community is negligible. Your vet needs to be educated.
Bob and Barbara run their sanctuary mentioned earlier for FIV and felv cats, and have produced a wonderful guide which if you pm me the address if your vet I will happily forward on to him.
As for her teeth, all 14 year old cats have some kind of tooth or gum decay, so just treat the condition for what it is. If it turns into stomatitis you may wish to consider extractions but ordinary gingivitis is not generally connected with the virus.
The likelihood is she has always had the virus, so why should she be treated any differently now? Stats suggest that up to 40% of the UK population of feral and stray cats may be infected with FIV. I suggest this proportion is likely to be reflected in the domestic cat population as well, but stats only record the cats actually tested for the condition, healthy cats generally do not get tested and as the vast majority of FIV positive cats live full and healthy lives they never figure in the stats. This means the stats are likely to be drastically disproportionate as only sickly cats would figure in the stats!
Please don't panic, find a new vet who appreciates the correct thinking on FIV and get on with enjoying your cat.
