Well, I just wrote a long response and accidentally pushed some button that took me to a different thread, so I lost the post.
Here's my take on the vet situation. Vets are obligated to focus on the risk. That said - some vets are more knowledgable about FIV than others. Some are not up-to-date on the literature, and know what they read about it five years ago. Others don't know the difference between FIV and FeLV. It's going to be up to you to read up on FIV and figure out where your vet stands in that group.
The bottom line is that your boys do roughhouse enough for one to have an infected... bite wound? If it was a scratch, that doesn't transmit it, because that's not saliva-to-blood or mucouse membraine. But if JD has gingivitis and bit Brooks, he's potentially already been exposed. (No point in testing him for another few months though).
The other thing to consider is that there are false positives. In fact, I think about 30% (sorry, I don't remember the number, but it's pretty high) of tests are false positives. That's why if you can afford it, it's best to follow-up the SNAP (ELISA) test with the Western Blot. Where we live, the Western Blot costs about $135 - $145. It tests for two specific antibodies, and is a confirmatory test (no false positives in cats older than six months).
Your vet should be knowledgable about your cats, how they interact, and your specific situation. So I wouldn't completely discount the advice. But I'd take it in view of other information you're learning about FIV. It lives outside of the body for a few seconds (unlike FeLV, which is believed to exist outside of the body potentially for hours). FIV is transmitted via saliva to blood or mucous membrane, and it is generally thought to require the deep tissue penetration for "incubation," though there is a risk with cats that have compromised immune systems that transmission from an FIV+ kitty could be more "casual."
But the bottom line is that FIV is such a slow acting virus that from the time of initial infection it generally takes a minimum of six weeks and up to three months for there to be detectable levels of virus in the cat. So take our Chumley as an example. We trapped him as part of a TNR program, but didn't want to release him because he became people-friendly quickly - and was SO cat aggressive, he scared all the ferals away. During the neuter, they treated him for an abscessed bite wound. The foster network couldn't take him right away - but if they could, he likely would have tested negative for FIV. As it was, he lived inside on his own for about six weeks until they DID have room for him. THEN we took him to be tested - and he tested positive.
But in a normal shelter-intake process, he would have tested negative. And he would have been adopted out as an FIV negative kitty. His family would have dealt with his diarrhea and his allergies &etc., all the time not knowing he had FIV. Let's say he lives in a home with other cats, indoor-only. In 5, 6, 7, 10 years... he gets some hard-to-treat illness. A vet thinks to test him for FIV. He would test positive. And everyone is left wondering - when and how did he become FIV+? And yet all the other cats in the home are still FIV-.
I don't know if I answered your question.
But hopefully we've all helped with information that will help you - with your vet - decide the best course of action.
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). Spend time on the 
! I did not mention it as it was not taught to me till just now.
I will just say that I agree with your veterinarian. But they are your cats and the decision is completely up to you.
!!! So glad your other cat tested negative and I am sure it will stay that way
