Throat Leech (Infestation, Vermin) CR 4
The throat leech is a one-inch-long gray leech that lairs in pools, streams, underground springs, and similar sources of fresh-flowing water. When a living creature consumes liquid containing a throat leech, the leech attaches itself to the back of the victim’s throat and begins draining blood. This deals 1d3 points of Constitution damage each round. Once the leech has drained 6 points of Constitution, it ceases draining (but does not detach). When a throat leech has sated itself, its body swells up, causing its victim to start to suffocate. A remove disease spell kills a throat leech as does a precise application of fire to the affected area (such as a heated wire or dagger tip) that deals at least 1 point of fire damage.
Throat Leech from the Tome of Horrors Complete, Copyright 2011, Necromancer Games, Inc., published and distributed by Frog God Games; Author Scott Greene, based on original material by Ian Livingstone.