As long as you cook the meat thoroughly, you should be fine. If it looks diseased, feed the other wildlife with it, not yourself. Like GT said, you'll know it when you see it. If you know the Bible, remember what is said about swine, there's a reason He said that. They are known to carry diseases.
Feral Hogs and Disease « Texas Natural Wildlife
Shooting from a stand or a tree is the safest. When you fire, the pigs will scatter, it's every pig for himself after the first shot. If you're hunting in dense vegetation, don't expect to kill very many, open ground is best. Or at least timber with little undergrowth. The younger the pig, the better the meat. It's best to hunt with a round that has some umf to it. Reason is that males develop a shield, for fighting, on their sides. It may sound like BS, but, the shield has been know to stop bullets (doesn't happen much though) and arrows from penetrating and causing death. Again, it doesn't happen much.
Is this hunt for meat or population control? If it's for control, hunting is actually a poor method. Large traps are best for control. If hunting at night, a spot/flood light with a red or green filter is a must. I favor green myself. I see better and see more with it, and it's easier on my eyes. They, like lots of animals, can't see red and green. Pigs have poor eye sight but can smell and hear very well. So if a pig runs at you, stand still and step out of the way if it is going to run you over. If it's not going to hit you, don't move, blind basturd can't see you but he can hear you. So running around won't help. They will run you over and get you if they get a chance though.
Two years ago my dad and I were squirrel hunting west of town on company land. We got down to a stand of pecans in a creek bottom. Dad stayed close to the fence line about a hundred yards to my right. I was walking through 8-12 foot tall weeds/Johnson grass. Heard some noise ahead of me, though it was cows since they were once run out there, but two big pigs ran by me, three feet to my right. A sow and young male. I could see them running around due to the grass movement, and hear lots of grunting. I believe they were looking for me. The male stepped out in the roughly 20ft diameter opening I was in, right in front of a massive pecan. I was hunting with my old Rem 870 with low brass 2-3/4" skeet loads. So I put 3 round in his face at close range. He scrunched up squealing louder than any pig I've ever heard. Reloaded (had the plug in it), three more shots, reloaded, three more shots, finally laid over, still alive though. One more round to the head with the muzzle 1" away finished him off. The female bolted on the first shot. Dad shot at her with his 20ga at 30yds but all it did was knock the dirt off her and she ran unscathed. Wasn't expecting contact so we didn't have pistols. All this happened in probably 30 seconds or so, I shot and reloaded as fast as humanly possible trying to avoid getting got. It felt like a lot longer to tell you truth. Anyways, pigs are tough animals.