What CAN survive/disseminate outside the colon?

Hi all,
My question is how can a person know what they are dealing with, what type species disseminated? Can Tapeworms disseminate into the body? I am still trying to figure this out. Maybe ICU or another expert can share what can survive in the body's extremities?

I used to have the urticaria rash on buttocks until herbs/dissemination. So I wonder if that is strongyloides?

Thanks for any insight in advance! Hopefully getting ELISA testing done if the lab can figure it out with having to mail the blood specimens.