How bad is it? It's very gross and lowbrow.
Should you see it? Yes, though it's hard to watch at times.
I was expecting this to be silly and campy, but it's in the vein of "Tokyo Gore Police," so it's wild, violent, gory, sick and still pretty funny, though the humor is about as base as one can get. A girl and her friends go camping and she intentionally swallows a parasite to keep her skinny, but it sends her running to an outhouse, where there are zombies hiding below. Soon, there are crap-covered zombies attacking and the girl tries to use her karate skills to stop them before discovering she can stop them with farting.