I took Marvin, my kitty, to the vet for his shots a month or so back. We got talking about Feline Immunodeficiency Virus, the cat equivalent of HIV. It can be transmitted between cats who are outdoors a lot and who fight with other cats...
Marvin fights all the time. He's missing part of one of his ears. At my old flat, there was a large white cat he had constant battles with. At our new place, he quickly carved out a territory, although there is a pesky grey cat who seems a bit quicker than he is. And occasionally steals his dinner.
So the vet suggested I get him tested. Long overdue, in retrospect. There is a vaccine that can be given, but it's useless if they're already positive.
Anyway, the test came up positive. I can't say I'm surprised.
FIV is less of a big deal than the human version. There's no reason he can't live out quite a long life (he's nine already). We just have to keep an eye on him and make sure any cuts or infections he gets are treated quickly. We also need to keep him indoors as much as possible, so he doesn't infect other cats. Which is going to be hard given what a determinedly outside cat he is. So in practise, we're going to keep him inside at night, when cats fight most.
Hopefully he should be OK. He has a mild cat cold at the moment, so we're having to feed him pills twice a day - which is interesting. He hates pills, hates being restrained and has big teeth and claws! So I've been sneaking it into his food, which seems to be working so far.