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

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 ’