- You may also be looking for the TNG holodeck character Felix Leech.
The leech was an animal that attached itself to another creature, usually absorbing some of its blood. It was sometimes used in medicine, though the practice had ceased by 2374.
The leech native to Earth consumed hemoglobin present in the blood of many other Earth organisms. (TNG: "Phantasms")
Doctor Phlox was fond of leeches as a snack. In 2154, he snacked on some leeches while dictating a letter to Dr. Jeremy Lucas. He also fed one to a begging Porthos after warning him that it would clear out the dog's intestinal tract. (ENT: "Doctor's Orders")
While experiencing Q's take on Robin Hood in 2367, Maid Marian (Vash)'s servant suggested using leeches to relieve her fever caused by the brain sickness she feared Marian had. (TNG: "Qpid")
The Emergency Medical Hologram of the USS Prometheus told The Doctor, after arriving in the Alpha Quadrant, that advances in medical equipment since the USS Voyager left meant that "scalpels and leeches" were not used anymore. (VOY: "Message in a Bottle")
In 2377, when The Doctor was forced to work aboard Hospital Ship 4-2, he complained "With technology this primitive you may as well be using leeches." (VOY: "Critical Care")