It's like if you go to a mall and test 200 people, you will probably find millions of germs, and what not on them. By keeping healthy and eating right, your body fights off any attempts for them to bring you down. Same rules really...
Germs or bacteria is one thing, worms, flukes and protists is another.
I was quite surprised by the heavy load and variety.
Basically in humans the organisms are different but the equivalent of, malaria, sleeping sickness, entamoeba, giardia, cryptosporidium, hookworm, tapeworm, pinworm, liverflukes.
I'm not sure I'd want to be shopping in that mall
... and I certainly wouldn't be eating amazonian sushi.