What disease or parasite would cause such severe brain damage to a man he would intentionally insert his penis into human feces?

Answer 1

It's not about brain damage. The man in question has a fetish called "coprophilia" -- an erotic attraction to feces. Most people would find this pretty gross, but it's his business, not ours.

Unless, of course, it is yours because you're his partner or spouse. In that case, you need to have a serious talk about what happens when a fetish becomes more important than real live human beings. It's also worth saying that messing with feces can cause an infection. Let's hope the man knows what he's doing and that he's taking proper precautions.