- You may be looking for the Regellian blood worm.
A Regulan bloodworm.
The Regulan bloodworm is a creature native to the Regulan system. It has been described as soft and spineless. Medically, it is quite useful for cleansing a being's lymphatic system. (ENT: "Doctor's Orders")
In 2151, when suffering from inadequate hibernation, Doctor Phlox suggested the use of Regulan bloodworms to filter a toxic antigenic compound in Ensign Travis Mayweather's bloodstream. Believing that fresh bloodworms would be more effective than ones from Enterprise's sickbay, Phlox contacted the starship's bridge and gave the order to travel to Regulus at maximum warp. The doctor eventually treated Mayweather with the proper medication. (ENT: "Two Days and Two Nights")
In 2153, Captain Archer ordered that Phlox should develop a memory removal syrum to use on the Xindi-Primate Degra, to erase his short-term memories, so the Captain could extract information from him about the location of the Xindi superweapon. The use of a harmless Regulan bloodworm was a ruse to gain Degra's trust more easily.(ENT: "Stratagem")
Korax, a Klingon Defense Force lieutenant, once insultingly compared Humans to Regulan bloodworms on Deep Space Station K-7 in a conversation which immediately preceded a barroom brawl. (TOS: "The Trouble with Tribbles")
Information about Regulan bloodworms was displayed by the computer as an okudagram graphic in Keiko O'Brien's schoolroom on Deep Space 9. (DS9: "A Man Alone", "The Nagus")
A graphic of a Regulan bloodworm was also displayed in the infirmary aboard Deep Space 9. (DS9: "Babel")
Background
A Regulan bloodworm (bottom middle-left)
The computer display in the schoolroom described data taken from a 1977 reference work, the Star Fleet Medical Reference Manual, coincidentally co-authored by art contributor Doug Drexler.
The reference to Regulan bloodworms by "Trouble with Tribbles" writer David Gerrold was never followed by an explanation of what they did to get the name "bloodworm", and it was never revealed which of the planets orbiting Regulus the worms originate from; according to the schoolroom display, however, the homeplanet of the bloodworm is Regulus II.
Gerrold reportedly pitched a script for Star Trek: The Next Generation involving infections of bloodworms carried by helpless victims. The story used bloodworm infection as a metaphor for the 1980s AIDS crisis, describing the same kinds of mistreatment and persecution of carriers.