A leech (genus: hirudinea) was a worm-like animal which fed on blood. (AUDIO: City of Spires [+]Simon Bovey, Main Range (Big Finish Productions, 2010).)
Leeches were sometimes used for medicinal purposes. Sir Isaac Newton once refused an offer of help for one of his seizures, as he knew it would involve leeches. (AUDIO: Summer [+]Mike Maddox, Circular Time (Main Range, Big Finish Productions, 2007).) In 1794 Paris, a physician claimed he needed to go collect some leeches to treat Susan's illness. (TV: The Reign of Terror [+]Dennis Spooner, Doctor Who season 1 (BBC1, 1964).) When Barbara Wright offered Vicki some aspirin, Vicki compared taking the pills to sticking leeches on someone, as both treatments seemed medieval to her. (TV: The Web Planet [+]Bill Strutton, Doctor Who season 2 (BBC1, 1965).) On Arcadia, leeches were used to try to treat Elaine Delahaye's madness. (PROSE: Deceit [+]Peter Darvill-Evans, Virgin New Adventures (Virgin Books, 1993).)
In 1699 on the Fancy, a leech bit De Florres, causing the Siren to take him to her ship. (TV: The Curse of the Black Spot [+]Steve Thompson, Doctor Who series 6 (BBC One, 2011).)
In 1965, Alexander Lullington-Smythe was temporarily transformed into a leech by the Latter-Day Pantheon. (PROSE: Salvation [+]Steve Lyons, BBC Past Doctor Adventures (BBC Books, 1999).)
Sarah Jane Smith was bitten by several leeches during a visit to Papua New Guinea. (PROSE: Conscription [+]Error: Code 2 - no data stored in variables, cache or SMW.)
The Fourth Doctor called the Collector a blood-sucking leech. (TV: The Sun Makers [+]Robert Holmes, Doctor Who season 15 (BBC1, 1977).)
Mula compared Zanak to an enormous leech after the Fourth Doctor explained how it consumed other planets. (TV: The Pirate Planet [+]Douglas Adams, Doctor Who season 16 (BBC1, 1978).)
The Eighth Doctor called Miraculite a leech. (AUDIO: Faith Stealer [+]Graham Duff, Main Range (Big Finish Productions, 2004).)
The Process resembled a giant leech. (PROSE: Cat's Cradle: Time's Crucible [+]Marc Platt, adapted from Cat's Cradle, Virgin New Adventures (Virgin Books, 1992).)
Azoth created leech-like creatures and placed them in humans as part of his plan to destroy the Beast. (PROSE: The Taint [+]Michael Collier, BBC Eighth Doctor Adventures (BBC Books, 1999).)
Pelt was attacked by leeches on a planet in the Quadrille. (PROSE: The Dalek Factor [+]Simon Clark, Telos Doctor Who novellas (Telos Publishing, 2004).)
The Eighth Doctor and Perfection encountered leeches on an island in the Divergent Universe. (AUDIO: The Next Life [+]Alan Barnes and Gary Russell, Main Range (Big Finish Productions, 2004).)