As someone with ulcerative colitis myself, I haven't heard of a parasite causing colitis. Usually, the cause is unknown and it's a chronic condition. I'm certainly no expert, but if it is truly just a temporary issue, that's great! Although even if it lingered, it shouldn't cause much of an issue as long as its mild to moderate. There are several NFL players that have dealt with similar issues, such as David Garrard, Rolando McClain, and a few others I can't remember off the top of my head.
Best of luck to him. As an NC State guy, I've been rooting for him, obviously. He's got talent. The mental aspect of his game will dictate how far he goes, imo.