The Danaxian tapeworm was a parasitic organism that attached itself to the lower intestinal tract and absorbed nutrients from its host. Extracting it was a simple procedure that required the insertion of a standard V-probe into the body.
Phlox used one as a "perfectly harmless" way to lose weight in late 2153 or early 2154. Trip Tucker found the practice gross and interrupted Phlox before he could elaborate further. (ENT: "The Council")