Out on a limb for leeches

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Dad loved his garden pond. Here he is feeding the fish a couple of years ago.

This column appeared in the Darlington & Stockton Times on 2nd February 2018, & the Gazette & Herald on 31st January 2018.

I went through the ‘frogs and snails and puppy dogs tales’ phase with each one of my three boys when they were at primary school. They were fascinated by ‘minibeasts’, which was a new word to me, but referred to what we would have called creepy crawlies. They had no squeamishness about picking up spiders, worms, slugs, snails and wood lice and presenting them to me with great glee.

Even more excitement was to be had whenever we came across a pond, as there were more fascinating minibeasts to found in and around it. When my oldest was a toddler, we lived in house with a pond in the garden and I can’t forget the noise the frogs used to make, and the undulating surface of the water, during mating season. The females are attracted to the males with the loudest croak, hence the cacophony! They also lay up to 2000 eggs, so soon our pond would be teeming with tadpoles, although not all would make it to adulthood, and those that did risked a messy confrontation with the lawnmower if they ventured far from the water.

My brother was also fascinated with such creatures in his youth, and in his February 4th 1978 column, Dad recalls the occasion when he built his own pond. Finding that a hole in the ground lined with polythene was no good, my brother resorted to using an old, Belfast sink, sunk into the rockery outside Dad’s study window. He filled it with with plants and pond life gathered from a local disused swimming pool and nearby lakes. He was very proud that soon his family of great crested newts had started breeding. He wouldn’t have known that 40 years later, if he disturbed the habitat of a great crested newt, he’d face up to six months in prison and an unlimited fine!

Alongside newts, frogs, sticklebacks and minnows, he also unwittingly rehomed a number of freshwater leeches, thankfully a small variety which were harmless to humans.

In medieval times, doctors were called ‘leeches’ due to their custom of treating all manner of ailment by bleeding their patients with the sluglike bloodsuckers. For many centuries, it has been one of the most effective treatments for a number of reasons, and this medical practice continues to this day. There is a farm in Wales which breeds medicinal leeches for this purpose, which is known as hirudotherapy (from the Latin name for these leeches, hirudo medicinalis). As well as supplying the NHS, the company sends them all over the world for use in surgery. The leech, which is about three and half inches long, is particularly effective in treating areas of poor circulation, especially in parts of the body with delicate soft tissue, for example when surgeons are trying to repair or reattach a severely injured limb. They clean up the wound by removing the clotted blood that is inhibiting blood flow, and then encourage circulation to restart.

It is the mechanics of mouth of the leech, a curious biological triumph, which makes it so effective for medical treatment. It has a circular, overlapping lip, and then three jaws, shaped a bit like the Mercedes-Benz logo, each with a row of 100 tiny teeth, perfect for making clean incisions into the skin at exactly the right depth. As they bite, they secrete a local anaesthetic, making the bite painless, alongside another substance, known as a vasodilator, which stimulates blood flow. Once the leech has filled its boots with blood, it then simply drops off to digest it. However, it leaves behind two important chemicals called hirudin and calin, which prevent further clotting and continue to stimulate blood flow for up to 48 hours after the leech has dropped off, which is so important when when it comes to success in treating these kinds of injuries. Although it all sounds a bit gruesome, it is one of nature’s amazing accomplishments, far more effective than many other medicinal treatments, and in fact the leeches only consume a relatively small amount of blood before they become full, around 15ml.

Incidentally, trials have shown that the anti-inflammatory and anaesthetic properties of leech saliva have been shown to be effective in treating pain and tenderness in the joints of people suffering conditions such as osteoarthritis. Vets are also finding them useful during surgical procedures on animals.

Now my question is, how would you feel with a leech let loose on your injured limb?
(Sources: biopharm-leeches.com, guysandstthomas.nhs.uk).

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