Leeches: From ancient times to modern medicine

Clinical
By
Dr Leigh Dayton
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From ancient bloodletting to modern microsurgery, the humble leech has evolved from feared parasite to an unlikely yet powerful medical ally.

Imagine the ultimate movie monster. Its body is divided into 34 segments. It has two hearts, two or three jaws, and powerful suckers on its mouth and anus. A bloodthirsty hermaphrodite, the scary beast gorges on enough blood to triple in size after biting onto its victim. It even eats its own kind.1–4

It is – yes – a leech. And Australia is home to 70 of the world’s 500 species, including Richardsonianus australis, Hirudo verbana and Hirudo medicinalis. Most species are aquatic, but in Australia and Southeast Asia, some live on land.3–6

As the name Hirudo medicinalis suggests, the species’ blood-sucking capability has been exploited for thousands of years. The earliest well-documented record of its use dates to 1500 BCE in Egypt. In the first century AD, Pliny the Elder used leeches to treat phlebitis and haemorrhoids. Napoleon’s surgeon Jean Dominique Larrey claimed they were a cure-all.6–8

With such high-profile advocates, it is no surprise that by the 18th and 19th centuries leeches were used widely across Europe. They provided treatment for diverse conditions, ranging from battle wounds and headaches to infections and unbalanced humours.9

But having reached their popularity peak, the use of leeches gradually declined until the 1980s. That is when the slimy squigglers scrubbed up and began assisting surgeons as a ‘living, breathing medical device’.7–11

Ms Latrille

This role was officially acknowledged in the US in June 2004. That is when Dr Celia Witten of the US Food and Drug Administration wrote to Brigitte Latrille, head of the French firm Ricarimpex SAS. Witten approved the sale of medicinal leeches for the purpose of treating post-surgical venous congestion. No formal approval to sell medical leeches – Witten’s ‘unclassified device’ – exists in Australia.12

Maintain the flow

Leeches are ideal assistants for reconstructive and microsurgical procedures. They are considered a ‘nonsurgical option’ for helping save reattached body parts like severed fingers, toes and ears.13

These procedures are successful up to 98% of the time. But a condition called venous congestion may occur when the thin-walled veins cannot carry the blood away. Instead, the blood pools in the veins and is unable to flow to the lungs and heart for reoxygenation.7,13

Ordinarily, leeches help keep blood flowing thanks to hirudin, an anticoagulant and antiplatelet agent in their saliva. The saliva also contains roughly 100 other bioactive substances that trigger anti-inflammatory, bacteriostatic, analgesic and many more actions. Collectively, this activity is known as hirudotherapy.10,14

Home sweet home

Back in Pliny’s and Napoleon’s days, leeches were scooped from ponds, lakes and slow-moving streams.6 Today, they are usually bred in sterile, controlled environments like Minibeast Wildlife’s Bugshop in Queensland.15

Australia’s leech farmers Brian and Carol Woodbridge are the exception. Pliny-style, they breed them in a water channel off the Murray-Darling Basin near Echuca, Victoria. A few years ago, Brian estimated they sold about 5,000 annually. ‘[But] it’s a bit hard to do a stocktake,’ he joked.6,8,16