Hookworms are an intestinal parasite that sucks blood from the walls of the intestines. They can be acquired either through ingestion of or skin penetration by infective larvae, I know that people can pick up hookworms by walking around barefoot on infected ground. I'm not sure how that would work with a snake that has scales but I would imagine that it's possible for them to pick up the parasite by slithering through infected feces if the larvae can worm they're way up to the skin between the scales

Mark