A cestode (parasite), Hymenolepis nana aka the dwarf tapeworm. Spread human to human. World wide in distribution.
Human to human (fecal-oral).
Mild abdominal discomfort.
And there is this really creepy case where there tapeworm underwent malignant transformation and became a tapeworm tumor. EEEUUUUWWWW. (PubMed)