Regulan Bloodworm

Regulan Bloodworms (Regulani vermis) are small, parasitic worm-like organisms native to planet Regulus II, in the Regulan System. Their bodies are soft and spine-less and they have long thin tendrils protruding from the anterior portion of the body. The Bloodworms are used in medicine, at least by Dr. Phlox, who states that the creatures are quite useful for cleansing the host's lymphatic system.

Behind the scenes
According to an unproduced episode of Star Trek: The Next Generation, they are also capable of infecting a host causing a deadly disease. The scientific name Regulani vermis and the anatomical diagrams come from the reference book Star Fleet Medical Reference Manual.