The love bite of a leech

Closely re­lated to earth­worms and used for hideous blood­let­ting since the Mid­dle Ages, the trans­gen­der medic­i­nal leech now helps to con­trol scar tis­sue fol­low­ing re­con­struc­tive surgery, dis­cov­ers David Pro­fumo

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The medic­i­nal leech still has a role to play in mod­ern medicine, re­ports David Pro­fumo

ONCE widely con­sulted as a weather prophet and with an en­dur­ing rep­u­ta­tion as both a loathly blood­sucker and a source of heal­ing, the medic­i­nal leech is now quite rare in the wild. There are some 600 species of leech world­wide, not all of them san­guiv­o­rous. Our two prin­ci­pal va­ri­eties are the car­niv­o­rous horse leech (Hae­mopis san­guisanga) that has no equine con­nec­tion, ‘horse’ be­ing merely an old word for ‘coarse’, and Hirudo

medic­i­nalis it­self, an am­phibi­ous in­ver­te­brate with nat­u­ral stocks now con­fined to a few pop­u­la­tions around Kent and Nor­folk.

Closely re­lated to earth­worms, they pos­sess a flex­i­ble, hy­dro­static skele­ton, 10 stom­achs along each side of the body, a sheathed pe­nis and a fe­male ori­fice. The anus is no­to­ri­ously hard to lo­cate, its usual po­si­tion be­ing oc­cu­pied by a pos­te­rior mouth. Al­though her­maph­ro­ditic, leeches do cop­u­late, but al­ter­nate gen­der dur­ing their life­time. Per­haps not ex­actly a beau­ti­ful worm, its slightly flat­tened olive-green body sports sev­eral thin or­ange lines and can in­crease to six times its length when en­gorged.

Vig­or­ous swim­mers, leeches on land haul them­selves along cater­pil­lar-style us­ing their suck­ers, only the front one of which has mouth­parts. The three ser­rated jaws leave a pain­less, Y-shaped bitemark re­sem­bling a Mercedes logo; leech saliva con­tains the an­ti­co­ag­u­lant hirudin, a syn­the­sised ver­sion of which (bi­valirudin) is used to pre­vent post-op­er­a­tive blood clot­ting in mod­ern medicine.

The leech used to be a pop­u­lar cot­tage barom­e­ter, slink­ing to­ward the top of its flask of liq­uid at the on­set of rain and twitch­ing as thun­der im­pended. The hap­pily named Dr Mer­ry­weather of Whitby de­vised—for the Great Ex­hi­bi­tion of 1851—an ‘at­mo­spheric elec­tro­mag­netic tele­graph’, con­tain­ing a dozen leeches that rang a bell when stormy weather was in the off­ing.

In many cul­tures, ther­a­peu­tic blood-let­ting by var­i­ous meth­ods (scar­i­fy­ing, cup­ping, ve­ne­sec­tion or leech­ing) was be­lieved ben­e­fi­cial to the bal­ance of hu­mours in the body and the prac­tice cer­tainly dates back to Homeric times, as well as fea­tur­ing in an­cient Ayurvedic tra­di­tion. In­deed, some say the pat­tern of Pais­ley fab­ric de­sign was based on an In­dian leech.

In Eng­land, there is a quite sep­a­rate An­glosaxon word laece—a homonym that means ‘healer’ and re­lates to ‘leechcraft’ as an early form of pre-sci­en­tific treat­ment in­volv­ing herbal­ism and charms to com­bat ail­ments that in­cluded elf-hic­cups and the Evil Eye, but not prin­ci­pally con­cerned with ap­pli­ca­tions of the blood-suck­ing par­a­site. How­ever, these con­no­ta­tions of heal­ing have grad­u­ally ac­crued to H. medic­i­nalis down the cen­turies.

From the Mid­dle Ages on­wards, leeches were used where a more vi­o­lent lanc­ing of veins might not be ap­pro­pri­ate—for chil­dren or preg­nant women, for in­stance. They were sup­pos­edly used to draw out im­pu­ri­ties from those af­flicted with ul­cers, her­nias, car­ci­no­mas or piles and ac­quired mor­bid as­so­ci­a­tions by be­ing fre­quently ad­min­is­tered to the dy­ing (Stalin’s doc­tors even tried this at his deathbed). Apothe­caries sold them and monas­ter­ies of­ten had special hold­ing ponds, as rou­tine bleed­ing be­came a re­li­gious rit­ual.

Leeches were metic­u­lously se­lected and cleansed and much care was needed in their han­dling as they can be mer­cu­rial—some­times grow­ing dozy and be­ing re­vived with a splash of wine, at other times re­quir­ing forcible re­moval from the epi­der­mis with horse­hair or ashes. Elab­o­rate ‘glasses’ and other ap­pa­ra­tus evolved for the trans­port and con­fine­ment of these lit­tle suck­ers: a no­table haz­ard of us­ing leeches is that, un­su­per­vised, they do have a pen­chant for dis­ap­pear­ing into var­i­ous bod­ily ori­fices.

His­tor­i­cally, the method of catch­ing them was to stand bare­legged in suit­able wa­ter and then de­tach them from your skin. Wordsworth’s some­what ro­man­ti­cised por­trait of his no­ble old rus­tic leech-gatherer in Res­o­lu­tion

and In­de­pen­dence tes­ti­fies that, al­ready in 1802, there was a prob­lem with over­har­vest­ing, such was the de­mand from Europe’s hos­pi­tals.

This vogue reached its zenith in postrev­o­lu­tion­ary France, with a mil­i­tary physi­cian named F.-J.-V. Brous­sais, who oc­ca­sion­ally at­tached 50 leeches to a sin­gle pa­tient and even used them to treat his fight­ing cocks. Par­tially thanks to this vam­pire de la méde

cine, France im­ported some 42 mil­lion leeches in 1833 alone and ar­ti­fi­cial hiru­di­cul­ture be­came an in­ter­na­tional trade.

For­tu­nately, the ma­nia for Brous­saism was as short-lived as many of his pa­tients, but leech­ing didn’t be­come en­tirely re­dun­dant as a clin­i­cal tool and is used today to treat ev­ery­thing from os­teoarthri­tis to pri­apism and can play a use­ful role in the con­trol of scar tis­sue fol­low­ing re­con­struc­tive or plas­tic surgery.

In pop­u­lar cul­ture, the leech has long been equiv­a­lent with greed and was a sta­ple of po­lit­i­cal car­toon­ists dur­ing the Vic­to­rian era. It has also fur­nished many a hor­ror­film mo­tif, es­pe­cially in the works of Cana­dian di­rec­tor David Cro­nen­burg (nick­named the Baron of Blood), who used to keep a pet leech in his fridge: Shivers (1975) and

Rabid (1977) fea­ture leechly images so graphic that even the good Dr Brous­sais would have spilt his pop­corn.

‘Cana­dian film di­rec­tor David Cro­nen­burg kept a pet leech in his fridge ’

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