FOR MOBILE PLAYERS ONLY:

These can be found in swamp dungeons, one will spawn in the water at fountains at a high level, and you will be guaranteed to find them for every fountain that exists in that dungeon. If one latches onto you they can be removed by stepping into a poison gas vent, same thing applies to diseased leeches too as they also have a chance to spawn there.

FOR MOBILE PLAYERS ONLY: